Materials Genome Initiative for Global Competitiveness
C. Ward, Air Force Research Laboratory, AFRL/RX, Materials and Manufacturing Directorate, WPAFB, OH
In June of 2011, President Barack Obama launched the Materials Genome Initiative for Global Competitiveness (MGI) to develop an infrastructure to accelerate advanced materials discovery and deployment in the United States. Creation of an MGI infrastructure will require technological advances in digital data, experimental, and computational tools. The infrastructure will seamlessly integrate into existing product-design frameworks to enable rapid and holistic engineering design. This talk will provide an update on Federal investments to stimulate computational capabilities, data management, and an integrated approach to materials science and engineering.
Overview of the Advanced Manufacturing Partnership
A. Kracke, ATI Metals, Monroe, NC
On June 24, 2011 President Obama announced the launch of the Advanced Manufacturing Partnership (AMP). AMP is a national effort, recommended by the President’s Council of Advisers on Science and Technology (PCAST,) bringing together industry, universities, and the federal government to invest in the emerging technologies for the purpose of creating high quality manufacturing jobs and enhance our global competitiveness. The President’s quote in the announcement was, “Today I’m calling for all of us to come together – private sector industry, universities, and the government – to spark a renaissance in American manufacturing and help our manufacturers develop the cutting-edge tools they need to compete with anyone in the world.” From July 2011 through March 2012 representatives from twelve industrial companies, six universities, and numerous federal agencies met to investigate, analyze, and discuss issues and problems facing U.S. manufacturing today and in the future. This presentation will review AMP’s organization, findings, recommendations, and status.
Advanced Manufacturing Research and Education: New Technologies and New Degrees
D. Hardt, Massachusetts Institute of Technology, Cambridge, MA
This presentation will address some of the new most promising areas of advanced manufacturing technology, which can form the basis for new industries and new products, and a novel educational program that is part of an effort to prepare US industries for global leadership in manufacturing . The former will include a brief discussion of processes for the scale up of micro and nano-scaled processes, as well as exciting areas such as printed electronics and a new look at additive manufacturing. Switching to a more US Industry focus, the latter will present a novel degree at MIT that aims to create and strengthen the profession of manufacturing. The key elements of the degree are admission based on a significant interest in a manufacturing career, a closely coordinate, project based curriculum, and a team-oriented, industry based project in lieu of a research project.
The Role of Professional Societies in Supporting Materials and Manufacturing Innovations
S. Henry1, W. Hunt2, G. Spanos3, (1)ASM International, Novelty, OH, (2)The Minerals, Metals, and Materials Society, penn, PA, (3)The Minerals, Metals, and Materials Society, Penn, PA
Representatives from ASM and TMS will review how they are responding to the Advanced Manufacturing Partnership, the Materials Genome Initiative, and similar programs that are dramatically changing the information, education, collaboration, and networking needs of their membership and the broader communities and industries they represent. Increased collaboration and cooperation will be essential to meet the goals of these initiatives, and the societies will describe how they are working together and fostering teamwork among industry, academia, and government groups to accelerate materials and manufacturing innovation. Initiatives to be discussed include Materials Innovation@TMS programs supporting accelerated discovery, development, deployment, and manufacturing of materials and the recently announced ASM Center for Computational Materials Science and Engineering Data. Particular emphasis will be given to projects related to aerospace structural materials
Big M Manufacturing of small m materials
B. Wang, Georgia Tech, Atlanta, GA
This presentation will provide an overview of the Big M Manufacturing at Georgia Tech: what it means, what the enablers are, and who the stakeholders are. A case study that involves the development of nanotube buckypaper will be used to illustrate some aspects – processing, characterization, applications and supply chains – of Big M Manufacturing.
A Review of Titanium Casting Development for the F -22 Raptor
H. Phelps1, J. D. Cotton2, (1)Lockheed-Martin, Marietta, GA, (2)The Boeing Company, Seattle, WA
The F-22A Raptor is the first, high performance, fighter to use Ti-6Al-4V titanium investment castings in safety of flight applications. The last of the Raptor’s will be delivered to the USAF in 2012 and so it is an appropriate time to review the highlights of development work performed and technical challenges faced in the production application of Ti castings on the F-22. These include understanding the defects associated with the casting process, such as ceramic shell & hard alpha inclusions, porosity and weld defects. In addition, the methods used to mitigate defects in castings will be discussed including design & analysis considerations, improved detectability face coats and non-destructive inspection techniques. These aspects will be illustrated via discussion of the design evolution of the largest casting on the F-22, the aft side-of-body joint which underwent several design changes during the F-22 production run and was ultimately converted from a casting to a welded assembly due to the technical issues discussed. Finally, the presentation will include a discussion of design considerations to improve the likelihood of successful application of titanium castings on critical airframe structures.
Computational Design and Development of New High-Strength, High-Ductility Castable Titanium Alloys
J. Sebastian, J. Wright, H. J. Jou, S. Backs, QuesTek Innovations, Evanston, IL
QuesTek Innovations has applied its Materials by Design® approach to invent, design, and develop three new castable titanium alloys with strength and ductility characteristics similar to wrought titanium (e.g., wrought Ti-6Al-4V). The development of these alloys has been sponsored by a U.S. Army-funded Small Business Innovation Research (SBIR) program administered through Picatinny Arsenal, New Jersey. QuesTek’s titanium alloy computational design has considered a number of important factors including strength, toughness, alpha/beta transformation kinetics, and castability/solidification. The new alloys have been designed to be lower cost in terms of: 1) Near-net-shape formability (castability); 2) Raw materials (alloying additions); 3) Tolerance to impurities (e.g., oxygen and/or iron); and 4) Overall ease of processing (e.g., response to hot isostatic pressing, and overall microstructural and mechanical property robustness with respect to cooling rate after heat treatment). Results will be presented from initial prototype wedge castings, further commercial-scale ingot production, ongoing alloy specification development efforts (ASTM and AMS), and first-round Army component production and testing. QuesTek is seeking partnerships (titanium casting designers, titanium alloy producers, titanium foundries, etc.) to further commercialize its new castable titanium alloy technologies.
The Potential for High Strength Castings
J. Campbell, University of Birmingham, Birmingham, United Kingdom
Recent developments relating to casting production have indicated that improvements to ductility, toughness and fracture resistance of several hundred per cent seem attainable. This will be illustrated for Mg and Al alloys, steels and Ni-base superalloys. The essential condition is the control of bifilms which appear to be the initiator (probably the sole initiator) of cracking in metals. Traditionally this major factor controlling properties has remained neglected. Aspects of control and quantification of bifilm content of castings with a view to achieving the proper potential of metals will be outlined.
A20X - High Strength, Elevated Temperature Aluminium Casting Alloy
J. Forde, Aeromet International PLC, Worcester, United Kingdom
The aerospace and automotive industries are striving to reduce their carbon footprints and relative impact on the environment. New component design is being driven by reducing component weight and increasing operating temperatures and pressures. Light-weight, high strength materials are at a premium in terms of both aerospace and automotive design. Historically, wrought aluminium such as the 2000 and 7000 series alloys exhibit respectively higher strength and superior elevated temperature properties than cast alloys. High strength/elevated temperature aluminium-copper based cast alloys do exist (A201/K-01), however difficulties associated with the ‘castability’ of these alloys has limited the widespread integration of these alloys particularly in the aerospace industry. ‘Castability’ issues include; severe hot-tearing, a high susceptibility to the formation of shrinkage porosity, segregation and compositional inhomogeneity, mechanical property inconsistency and poor weldability.
Aeromet International Plc have developed ‘A20X’, a modified version of A201 where the aforementioned issues have been eliminated through small but significant compositional modifications resulting in alterations to the solidification mechanisms of the alloy. The castability of A20X is equivalent to current aerospace and automotive casting alloys allowing large and complex components to be cast. The modified solidification mechanisms allow for a significantly reduced feeding requirement and a reduction in the use of mould chills, thus resulting in simplified mould designs and increased metal yields even when compared to aluminium-silicon based casting alloys. A20X is highly weldable and its properties are comparable with both the 7000 and 2000 series wrought materials allowing castings to compete, realistically, with fabrications, forgings and machined from solid production routes.
Advance Lightweight Casting Technologies and the Use of Casting Simulation and on-Line Alloy Database
J. Shah1, T. Prucha2, (1)Product Development & Analysis LLC, Naperville, IL, (2)American Foundry Society, Schaumburg, IL
The presentation will out line the overall driving factors for the research; brief description of the technologies being developed, such as the casting process (MMC, dual-phase iron) and alloy/material (7075 aluminum, ADI Austempered ductile iron, low cost Ti alloy and FeMnAl alloy - low density high strength steel) with benefits over currently used conventional alloys and processes; and potential applications and engineering data, useful for the design and materials engineers as well as system integrators of various military platforms. Each research areas will have the case study, which will include the application of the modern process modeling and simulation tool in assisting the design and manufacturing engineers. Some of the case studies will include the actual demonstration test articles designed, developed and fabricated for the current military programs. In some cases, relative cost comparison over the current process and alloys will be presented also to assist design and manufacturing engineers make down selection. Also, there will be a detail description of the on-line casting alloy database search (CADS) tool and case studies will be presented describing how a design engineer can chose from various casting alloys and process applicable at it’s conceptual stage using CAPS (Casting Alloy and Process Selector) tool and how they can down select the applicable casting alloy and download the engineering data, including fatigue and high temperature properties for some alloys using CADS tool.
Evaluation of EV31A-T6 Magnesium Casting Alloy for Rotorcraft Applications
L. W. Weihmuller, Bell Helicopter -Textron, Arlington, TX
Castings offer a low cost manufacturing approach for many rotor-craft components. Aluminum and magnesium castings are used extensively for drive system transmission housings and provide an economical means to produce complex geometries with cored passageways for oil cooling. Other rotorcraft applications have utilized titanium, steel, and aluminum investment castings to provide an optimized geometry for specific loading applications. A brief overview of casting components in rotorcraft applications will be presented, along with a detailed evaluation of EV31A-T6 magnesium sand casting material.
EV31A alloy was developed by Magnesium Elektron (MEL) as a more producible alternative to WE43, and provides greater strength at temperature and corrosion resistance than traditional sand casting structural alloys such as ZE41A. Mechanical strength evaluations were performed on welded and non-welded cast material, along with quench media variations. Additionally, a demonstration casting was poured to evaluate the producibility aspects of a typical transmission housing.
The Competition for Castings in Aerospace
T. W. Scoville, The Boeing Company, Seattle, WA
The use of castings in aerospace has declined in recent new airplane designs. Improved efficiencies of mature processes such as high speed machining, the selection of new structural building materials, and the maturing of other near-net shaped processes are crowding the spectrum of applications where castings have typically reigned. Perhaps this niche is just being better defined. What types of applications have been successfully challenged? Where do castings continue to be the process of choice? Are there developments in casting processes, materials, or design methods that will enable them to find more application on future airplane platforms? This presentation will survey Boeing and other aerospace applications and industry developments to help answer these questions.
MAI PCC-1: "Use of Digital Radiography for Final Part Acceptance of Aerospace Castings"
D. A. Brayshaw, J. R. Barrett, PCC Structurals, Inc., Portland, OR
The use of digital media is a process improvement over the current film based radiography and holds the promise of faster cycle times, improved acquisition costs, being environmentally friendly, and is pervasive across the entire industrial supply base. Despite these benefits, the implementation of digital radiography has been slow due to many barriers and differences amongst the aerospace industry. A 3-year program was funded through the Air Force and the Metals Affordability Initiative to accelerate the introduction of digital radiography into the aerospace industry for castings. Team members of this program included: the Air Force, Boeing, Lockheed-Martin, GE-Aviation, Honeywell, Pratt & Whitney, Rolls-Royce, Howmet, PCC, GE Inspection Technologies, Fuji, North Star Imaging, VJ Technologies, and Yxlon. The program completed in January 2012 and the project team was successful in removing the following barriers to implementation:
These technical barriers have allowed for successful implementation of digital radiography into production of aerospace castings. Active conversion is currently taking place at both Howmet and PCC. Equipment has been purchased and multiple components are currently being inspected in production.
Ablation Casting Process Update
D. Weiss1, J. Grassi2, B. Cox2, F. Major3, J. Campbell4, (1)Eck Industries, Manitowoc, WI, (2)Alotech Limited, Brooklyn, Cleveland, OH, OH, (3)Rio Tinto Alcan, Québec, QC, Canada, (4)University of Birmingham, Birmingham, United Kingdom
The ablation casting process is a relatively new precision sand casting process in which the soluble binder for the mold is ablated (eroded) away by water jets prior to the freezing of the liquid metal, thereby solidifying the metal at unprecedented rates as a result of the direct impingement of cooling water (in contrast to most other casting processes whose rates of solidification are largely controlled by heat transfer across the ‘air gap’ between the casting and mold). In addition, environmental acceptability of this water-based process is high, but productivity and cost appear to be keenly competitive. Both magnesium and aluminum castings with high properties have been successfully demonstrated, with a significant number that have resisted all attempts to fail them by normal testing procedures.
High Strength Chill Cast 7075 Aluminum
D. Weiss1, T. D. Wood2, P. D. Fraley2, J. LaCosse3, P. G. Sanders2, C. Thorne1, (1)Eck Industries, Manitowoc, WI, (2)Michigan Technological University, Houghton, MI, (3)GS Engineering, Inc, Houghton, MI
High Strength Chill Cast 7075 Aluminum
The use of high strength 7075 wrought aluminum is widespread in the aerospace industry. The ability to shape cast the high strength 7075 alloy chemistry is desirable to reduce component costs. The high alloy content and corresponding large freezing range of the alloy present challenges related to undesirable segregation during solidification. By combining known foundry practices with high thermal conductivity and high heat capacity chills, high integrity shape castings can be produced with minimal segregation and a refined microstructure.
Chill casting of 7075 step plates and a vehicle component has been conducted through a DOD sponsored and American Foundry Society (AFS) managed program called Achieving Lightweight Casting Solutions (ALSC). It is demonstrated that by controlling the chemistry and cooling rate, wrought alloy mechanical properties can be achieved.
Aluminum Alloys for Aerospace Castings – Status, Challenges and Trends
M. Hartlieb, F. Major, Rio tino Alcan Inc., Montreal, QC, Canada
Aerospace aluminum castings are made from a wide range of alloys in various processes. Due to the relatively low volume (compared to automotive) and high precision required, investment and precision sand casting as well as PM are the most common processes, but for certain parts in higher volumes even high integrity diecasting is used. The different processes – together with the typically very high requirements of the components – determine the most suitable alloy (and temper). This presentation describes the most commonly used alloys for the different processes, the challenges and recent developments. The most common alloys for aerospace castings are typically high purity versions of the 356/357 alloy family (B and C356, E and F 357), high temperature alloys like C355, high strength alloys like the A or B206 or high integrity (primary) diecasting alloys The presentation describes trends and challenges of these alloys in terms of achievable properties, castability, opportunities of cost savings e.g. in heat treatment, etc.
Development of Sand Cast E357 Design Allowables for Incorporation Into MMPDS
T. Prucha, American Foundry Society, Schaumburg, IL
Design engineers need properties not based upon typicals but ones representative the of population variation observed in manufacturing that would be encountered as a function of different processes section thickness (cooling rates) encountered in complex casting designs and also from multiple supply sources. The requirements for components that are considered flight critical are even more demanding as the Federal Aviation Administration (FAA) FAR 25.613 requires statistically validated properties for structural materials and FAR 25.621 compels the use of casting factors, which means that a more conservative design approach is used which adds section thickness and weight. Currently, most casting alloys have no statistical validation and cannot be considered for replacement or new design without developing this data on a component by component basis. This expensive process requires an extraordinary business case analysis to justify this added expense and time delay. Yet this is routinely done in the jet engine business and is documented in the Metallic Materials Properties Development and Standardization (MMPDS) Handbook. The approach taken in this project was to develop statistical basis A & B design allowables for sand cast E357 for six thicknesses from 1/8 to 2.5 inches to supplement statistically based allowables for investment cast E357 at five thicknesses (< 0.500, 0.501-1.000, 1.001-1.500, 1.501-2.00, 2.001-2.500-inches) available in the MMPDS-05 Handbook. A consortium of casting users, foundries, suppliers and organizations that support metalcasting assisted in design of the test castings, devising the gating and rigging practice and manufacturing the tooling and test parts, establishing the melt and metal treatment, heat treatment and evaluation practice for the plates produced to develop these properties. Also critical was to demonstrate the utilization of Computer Aided Engineering and Modeling tools to create the tooling design as an approach to design reliability and repeatability into the process, also collect valuable information on the repeatability of inspection validation systems. This project was also to consolidate weld knowledge to develop an AFS Recommend Practice for the in-process weld repair of aluminum-silicon hypo-eutectic alloys and develop mechanical properties to demonstrate the efficacy of the practice, and develop statistical data that facilitates acceptance of weld practice.
Induction Heating of Ferrous Alloys Prior to Hot and Warm Forming
V. Rudnev, Inductoheat Inc., Madison Heights, MI
Presentation focuses on advances in induction heating of ferrous alloys prior to forging, rolling and extrusion. Besides through heating applications, presentation not will also discuss induction heating of selective areas of the workpieces. Good practices to ensure high quality of heated components (microstructural and thermal) will be revealed in this presentation. This includes review of measures to avoid intergranular cracking (incipient melting), excessive grain growth, oxidation and scale formation, etc.
The Need for Additive Manufacturing Capabilities in a DoD Depot Repair Environment
B. Boyette, R. Kestler, NAVAIR, Cherry Point, NC
DoD repair depots provide a unique opportunity for the implementation of additive manufacturing technologies. Depots scrap large numbers of components that are worn beyond usable limits due to the limitations of traditional manufacturing technologies used in component repair. The potential exists for large returns on investment in developing additive repairs for legacy components. Several opportunities will be presented along with discussion of which additive processes might be suitable for component repair as opposed to new manufacture. DoD platforms also face logistics hurdles in procuring parts that have been out of production for some years. The lead-times associated with retooling for and remanufacturing of legacy components can be years in some cases. This problem is compounded when considering the small lot sizes often required. Additive manufacturing has the potential to remedy this situation as well, which must be considered when considering the costs of additive parts.
Higher Productivity Laser Powder Bed Deposition
R. Freeman, E. Ashcroft, TWI Ltd, Cambridge, United Kingdom
There have been significant developments in the field of additive manufacture in recent years, and TWI has taken a strong lead in the area of Laser Metal Deposition (LMD) using blown powder and Selective Laser Melting (SLM) using powder bed systems.
This presentation cover the developments made in recent research work on making the process as productive as possible, including the following areas of work:
High Entropy Alloys
J. D. Cotton1, M. J. kaufman2, D. B. Miracle3, G. Wilks4, U. R. Kattner5, (1)The Boeing Company, Seattle, WA, (2)Colorado School of Mines, Golden, CO, (3)Air Force Research Laboratory, Dayton, OH, (4)General Dynamics, Inc., Dayton, OH, (5)NIST, Gaithersburg, MD
“High Entropy Alloys” are characterized as alloys consisting of roughly equal concentrations of at least five metallic elements and are claimed to favor close-packed, disordered structures due to high configurational entropy. Such crystal structures, e.g. face-centered cubic (FCC), hexagonal close-packed (HCP) and body-centered cubic (BCC), are advantageous in that they should offer multiple active slip systems usually observed in ductile metals and alloys. This opens the door to a large number of rich chemistries which would otherwise contain unacceptable volume fractions of intermetallic compounds to be useful in structural applications.
Despite thermodynamic arguments for entropic stabilization of simple, disordered phases, the high entropy alloys studied to date are typically combinations of elements with extensive solid solubility. For example, many investigated alloys are based on a cast CoCrFeNiX type base chemistry, where X = Al, Cu, Mo or Ti. Isolated research in other high-solubility systems, such as TaNbHfZrTi, has also been conducted. In the majority of papers, FCC and/or BCC crystal structures have been observed to predominate. In some cases, one compound-forming element, such as Al, is selectively added and appears to destabilize the FCC phase. Hence, the question the degree of influence of configurational entropy on solid solubility persists, and systematic studies comparing enthalpy (and compound formation) versus entropy stabilization (and disordered, crystalline solid solutions) have not been reported. Another issue is the dearth of reported tensile property data, which suggests there may be limited true ductility in reported chemistries. This could be discouraging for the development of future structural alloys. However, whether or not entropy plays a significant role in phase selection, the richness of the alloy design space and the breadth of microstructures that have so far been produced appear to offer possibilities for new discoveries and much to consider.
This presentation will review high entropy research to date and offer commentary on potential directions and applications, and also dicsuss some standing questions on the topic.
The Use of Micro-X-Ray Fluorescence in a Scanning Electron Microscope for Failure Analysis of Aerospace Materials
D. S. DeMiglio, Stork Herron Testing Laboratories, Charlotte, NC
Abstract Title: The Use of Micro-X-ray Fluorescence in a Scanning Electron
Microscope for Failure Analysis of Aerospace Materials
Authors: Daniel DeMiglio
Speaker: Daniel DeMiglio
Abstract: Micro X-ray fluorescence spectroscopy (micro-XRF) is a relatively new failure analysis tool. An X-ray gun with focusing capillary fiber optics interfaced with a scanning electron microscope (SEM) is used for semi-quantitative XRF microanalysis by energy dispersive X-ray spectroscopy (EDS). This paper will present a brief overview of how micro-XRF EDS can be a useful complementary microanalysis technique with electron beam EDS to obtain a more complete understanding of chemical composition in critical areas on a sample surface or where the volume of sample material is too small for conventional bulk chemical analysis. Some advantages to using micro-XRF include: higher X-ray peak to background ratios and greater beam stability for increased accuracy with standards as well as greater sensitivity for higher atomic number elements. Micro-XRF is well-suited to identification of non-ferrous materials and highly alloyed ferrous alloys. Examples will be presented of how micro-XRF and electron beam EDS have been applied to investigations involving alloy identification, contamination and wear particle analysis.
Advantages of the ForceMate2 Bushing Method for Composite Component Manufacture or Repair Applications
J. S. Ransom, K. S. Stow, Fatigue Technology,, Seattle, WA
Composite structures require holes to be machined for different attachment requirements. Liners or bushings can be used to protect the holes and provide wear surfaces in joints. ForceMate2 is a double bushing system that is radially expanded into the composite hole. The ForceMate2 process provides advantages for repair as compared to a single bushing or liner.
Three rework options will be discussed:
1) Inner bushing is worn out or ovalized – exchange of inner bushing only
2) Inner bushing badly damaged and outer bushing affected – repair outer bushing without removal and exchange inner bushing
3) Collateral damage on both bushings – repair composite with ream to oversize hole and exchange both bushings
The ForceMate2 system installs a bushing interference fit into the composite material and then draws an inner bushing into the hole in a single operation. The bushings can resist migration and axial movement without staking or bonding, though they can be installed with sealants or coatings if required for the application. In addition, the process has been tailored so that the inner bushing will move before the outer bushing to protect the composite material. The bushings are adapted to meet the customer’s unique needs. The expanded bushing process has been shown to achieve higher retention performance than shrink fit type bushing installations. Additional benefits of the ForceMate2 system besides the rework options include the use of flanges on both sides of hole, ability to install in areas of access restriction and the use of different materials for the two installed bushings.
High Interference Cold Expansion of Bushings Made From Copper-Beryllium Replacement "ToughMet 3" Alloy
L. Reid1, B. Bertin2, (1)Fatigue Technology,, Seattle, WA, (2)Materion, Placerville, CA
Extra precautions required to safely machine copper-beryllium alloys has driven the aerospace industry to find a replacement material with similar properties for use as a high strength bushing and bearing material. “ToughMet 3”, a Cu-15Ni-8Sn spinodal alloy is now successfully being used as an alternate alloy material. In service, it has shown to provide lower friction and increased wear resistance when compared to other copper based alloys used for bushings and bearings including copper beryllium. For high interference fit bushing installations, most aerospace companies use the ForceMate method to expand the bushing into a hole to create a high interference fit with a synergistic residual compressive stress around the hole. Fatigue Technology conducted a bushing removal force comparison between different bushing materials including copper beryllium (AMS 4533), 13-8 PH stainless steel (AMS 5629) and ToughMet 3 (AMS 4596). ToughMet 3 had greater retention than copper beryllium and also had a higher retained expansion in the parent material. This paper will discuss the evaluation and comparative test results between conventional shrink-fit and ForceMate installation methods for the different materials mentioned above along with FEA results of the retained expansion properties. The results showed conclusively that the ToughMet 3 alloy can be installed with the ForceMate method and will meet or exceed retention properties of copper beryllium.
NEW HYBRID SOL-GEL Coatings for Aluminium Alloys CORROSION Protection
M. J. Menu1, J. P. Bonino1, F. Ansart1, J. Esteban2, A. Uhart3, J. C. Dupin3, D. Gonbeau3, (1)Centre Interuniversitaire de Recherche et d'Ingenierie des Materiaux, Toulouse, France, (2)Messier-Bugatti, Molsheim, France, (3)ECP-IPREM , University of Pau, PAU, France
Sol–gel films are actively investigated from the last decade as possible candidates for environmentally friendly pre-treatments on metals [1-2].
However, the main drawback is the lack of active corrosion protection compared to chromate conversion coatings, particularly on aluminium alloys [3]. However, the environmental laws in many countries have imposed severe restrictions on chromate use due to its high toxicity and environmental hazards.
A new promising approach consists to use sol-gel process to prepare hybrid coatings containing cerium on aluminium substrates [4-5]. In this work cerium nitrate was used as additive to the hybrid sol–gel formulations in order to confer active corrosion protection without damaging the coating. The cerium nitrate was added at different ratios in the synthesis process to understand the role of possible interaction of the inhibitor with components of the sol–gel system. A series of microstructural and physico-chemical characterizations (X-ray photoelectrons and Auger spectroscopies, EIS) were performed on the coatings to understand the role of cerium, its spatial distribution (depth profiling) and an important focusing was made on the accurate characterization of oxidation degree of Ce (+III, +IV) within the solgel matrix as a function of the doping level and the composition of the solgel.
The results demonstrate that first, cerium nitrate do not affect the stability of sol-gel films and second, that this inhibitor plays two roles in the coating: first, an active role in corrosion resistance and second, an increase of polymeric network cohesion leading to a best adhesion on the metallic substrate due to a well-defined bond at the aluminium alloy/ solgel interface.
Present work belongs to SOLGREEN-Aerospace Valley consortium.
[1] K.A. Yasakau; M.L. Zheludkevich; O.V. Karavai; M.G.S. Ferreira; Progress in Organic Coatings, 2008, 63, 352.
[2] M.L. Zheludkevich; R. Serra; M.F. Montemor; I.M. Miranda Salvado; M.G.S. Ferreira; Surface and Coatings Technology, 2006, 200, 3084.
[3] M.L. Zheludkevich; R. Serra; M.F. Montemor; I.M. Miranda Salvado; M.G.S. Ferreira; Surface and Coatings Technology, 2006, 200, 3084.
[4] V. Moutarlier; B. Neveu; M.P. Gigandet; Surface and Coatings Technology, 2008, 202, 2052.
[5] A. Conde; A. Durán; J. J. de Damborenea; Progress in Organic Coatings, 2003, 46, 288.
Cerium Addition to Improve Both Chemical Structure and Corrosion Behaviour of a Sol-Gel Coating on Martensitic Stainless Steel
J. B. Cambon1, F. Ansart1, J. P. Bonino1, C. Santilli2, P. Hammer2, S. Pulcinelli2, S. Santagneli2, (1)Institut Carnot CIRIMAT, Toulouse University, Toulouse, France, (2)Instituto de Química, Universidade Estadual Paulista, Araraquara, SP,, Brazil
Stainless steels are highly used in the aeronautics field for the manufacture of structural parts. One of them, the CX13VDW martensitic stainless steel (X12CrNiMoV12-3), known for its good mechanical properties, has a poor corrosion resistance particularly in confined or severe environments. In the last decade, Cr(VI) based pre-treatments have been currently used for corrosion protection of different metals or alloys. However, these compounds are toxic and due to environmental regulations, will be definitely prohibited in a near future. Alternatives to replace Cr(VI) are studied and show advantages and drawbacks when sets of key properties have to be considered such as: corrosion resistance, adhesion of organic coatings, fatigue resistance, reliability and quality control. However, some of these alternatives are very promising.
In this paper, a process was developed to improve the corrosion resistance of the martensitic stainless steel. Organic-inorganic hybrid silane-alumina coatings were deposited onto stainless steel by sol–gel route using a dipping technique. Different amounts of Ce(NO3) (0 to 0.1 M) have been added in the matrix as corrosion inhibitor. Corrosion and mechanical properties of the coatings were evaluated by respectively electrochemical impedance spectroscopy and nanoindentation. The consequence is that a cerium concentration of 0.01 M into hybrid coating found to be optimal.
The effects of cerium concentration on the structural features of hybrid films were also studied by 29Si, 27Al and 13C nuclear magnetic resonance (MAS NMR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. It was shown a real influence of the inhibitor concentration towards the chemical structure of hybrid and therefore a possible correlation with the sol-gel coating anti-corrosion performance. In this paper, a focus is dedicated to explain why the cerium concentration of 0.01 M in the sol-gel matrix is optimal.
Low Cost Surface Treatment for Enhanced Wear of Stainless Steel Brake Components
L. Steele1, B. T. Brandewie1, J. Swank1, M. Adams2, (1)Goodrich Corporation, Troy, OH, (2)Tribology Testing Labs, Saginaw, MI
Aircraft braking components operate at high temperatures in extremely harsh service environments. This requires the use of expensive cobalt-base torque-drive inserts for demanding wear conditions in multi-disk A/C brakes. This paper will describe the benefits of using a low cost stainless steel drive insert treated with an adherent lubricious oxide coating for wear resistance against several types of torque-bar drive coatings. Reciprocating friction and wear testing, using a modified ASTM D5707 method, at different temperatures will be presented. Results from a new reciprocating galling-threshold test for several different wear-couples will also be presented.
Portable Ultrasonic Shot Peening Repair of Helicopter Components
J. A. Gran1, G. G. Liu1, J. H. Chang1, M. J. Kane1, R. Buckner2, R. Bilbrey2, (1)US Army, Redstone Arsenal, AL, (2)Avion Solutions, Inc., Huntsville, AL
Portable Ultrasonic Shot Peening Repair of Helicopter Components
John A Gran, George G Liu, Jung-Hua Chang, and Michael J Kane
U.S. Army RDECOM, Aviation and Missile RDEC, Aviation Engineering Directorate
Redstone Arsenal, Alabama, 35898
U.S.A.
Randy Buckner and Robert Bilbrey
Avion Solutions, Inc
Huntsville, Alabama 35805
U.S.A.
Abstract:
Many helicopter dynamic components are fatigue critical and depend on shot peening to enhance fatigue life and lessen the impact from field induced surface damages. These components require conventional peening at Army approved vendors during manufacturing or overhaul repair. A common question asked during overhaul or field repair is: Can these components be repaired with a portable shot peening device in the field rather than shipping the parts back to the shot peening vendor? This ability would significantly increase readiness and reduce repair and life cycle costs. Through a Small Business Innovative Research project, a test plan was developed by the Aviation Engineering Directorate of the U.S. Army Research, Development, and Engineering Command, and carried out in conjunction with Avion Solutions, Inc. The effort includes a detailed comparative analysis of ultrasonic shot peening versus conventional shot peening on commonly used metallic alloys, optimization of ultrasonic shot peening parameters, and understanding its impact on fatigue strength. Based on the study, several helicopter components have been selected for use of the portable ultrasonic peening repair. Some examples of actual repairs of helicopter dynamic components will be presented. Also, the variation of the ultrasonic parameters and their impact on peening intensity in one particular field repair application will be discussed.
Characterization of near Surface Conductivity Profiles of Shot Peened and Laser Peened Inconel 718
R. Chandrasekar, T. Lesthaeghe, A. M. Frishman, B. F. Larson, C. C. H. Lo, N. Nakagawa, Center for Nondestructive Evaluation, Iowa State University, Ames, IA
This paper reports on comparison studies of near surface conductivity profiles of Inconel 718 sample plates that underwent two types of surface enhancement treatments, namely shot peening and laser peening. Both treatments are used to introduce protective compressive residual stresses, but they are known to produce different surface conditions: shot peening introduces shallow compressive residual stresses and high percentages of cold work, while laser peening introduces much deeper compressive stresses at lower cold work percentages in the material. The objective of this study is to characterize the near surface conductivity changes induced by the two peening processes, and to examine the correlations of the conductivity changes with the residual stress and cold work profiles. This aims to evaluate the feasibility of characterizing nondestructively the surface conditions of peened engine components, especially the residual stress profiles, by means of conductivity profiling using a swept frequency eddy current (SFEC) technique. By way of approach, Inconel 718 samples were solutionized, solutionized and aged, or direct-aged to produce three different types of microstructures. The samples were shot peened and laser peened at different intensities. SFEC measurements were conducted before and after peening. Conductivity profiles obtained by model-based inversion will be presented for each of the two peening processes, and will be compared with the residual stress profiles measured by XRD in order to evaluate the ability of the SFEC technique to discriminate dissimilar material conditions and responses to the two peening processes.
New Chemical Free Black Coatings for Aerospace and Space Applications
J. G. Carton1, N. Cobbe1, J. O'Donoghue1, L. Pambaguian2, A. Norman2, V. Liedtke3, T. McCaul4, (1)EnBio Nova UCD, Dublin, Ireland, (2)European Space Agency (ESA), Noordwijk, Netherlands, (3)Advanced Aerospace Composites (AAC), Seibersdorf, Austria, (4)Astrium, Stevenage, United Kingdom
For many spacecraft missions, high emissivity black body coatings are required to help manage the radiative exchange between the external surfaces of the satellite and the space environment. Although a number of thermal coatings have been developed, many suffer from issues relating to adhesion, conductivity, and ease of application. Furthermore, those coatings which contain organic components can exceed current off gassing requirements. For space applications, there is the additional complication that they must survive in a very harsh environment (vacuum, thermo-cycling, UV radiation). There is therefore a requirement for a coating technology which can produce coatings which have good adherence, are conductive, and can survive in space. Such coatings would also be of interest to the aerospace industry. In this presentation a relatively new coating technology, CoBlast, has been used to deposit a powdered material on to a titanium substrate, resulting in a black body surface. CoBlast, replaces the oxide layer of reactive metals with a fused thin surface. Unlike many other coating processes, CoBlast is uniquely non-complex, requiring no thermal input, no wet chemistry and is performed in an ambient temperature and pressure environment. A number of different coatings have been produced on a titanium substrate, and the thermo-optical properties and conductivity have been measured. Microstructural analysis was also performed and the coatings have also been subjected to thermal cycling and thermal shock tests. Subsequent analysis demonstrates that the samples survive the various tests resulting in a coating which is robust, has good adherence, high emissivity and is conductive.
High Performance Thin Films for Aerospace Applications
A. N. Ranade, M. A. Matos, The Boeing Company, Seattle, WA
The usefulness of polymer-based materials and coatings in aircraft components is two-fold. First, weight reductions are highly desirable to decrease fuel consumption and second, polymer-based materials are usually less expensive and convenient to manufacture. However, when used in applications with strict optical requirements, these polymeric surfaces can be susceptible to erosion which results in increased haze and decreased clarity. For example, when staple materials such as polycarbonate or stretched acrylic are used in windows, windshields, and canopies, one of the drawbacks is the tendency to scratch and craze. Polymeric windows have been historically coated with polysiloxane or polyurethane based coatings to overcome this limitation by improving the surface resistance to scratches. Still, improvements to the processes involved can decrease the required long drying times and can offer long term solutions in which the resistance to erosion is maintained overtime. Advanced thin film coatings based on Plasma Deposition Technologies can improve the durability of many components on aircrafts. These technologies can be exploited to generate materials with high performance, which are also environmentally friendly and produced with waste free processes. We are currently focusing our efforts in the development and study of thin films to improve the resistance to material erosion on polymeric substrates with applications in the aerospace industry and defense.
Testing and Implementation of Non-Chromium Sealer for U.S. Air Force Anodizing Operations
E. Berman1, S. N. L. Clark2, N. Hughes3, M. Klingenberg4, R. Mason5, N. Voevodin6, (1)AFRL, Dayton, OH, (2)Concurrent Technologies Corporation (CTC), Fairborn, OH, (3)Landing Gear Process Engineering, Ogden Air Logistics Center, UT, (4)Concurrent Technologies Corporation, Johnstown, PA, (5)Concurrent Technologies Corporation, Largo, FL, (6)University of Dayton Reserach Institute, Dayton, OH
Ogden Air Logistics Center (OO-ALC), Utah, is the primary facility within the United States Air Force for maintaining and overhauling aircraft landing gear. Aluminum landing gear components are anodized at OO-ALC to provide enhanced corrosion resistance, paint adhesion, and wear resistance; a sodium dichromate sealing operation usually completes the anodizing process. However, this sealer contains hexavalent chromium, which is listed on the Environmental Protection Agency's list of industrial toxic chemicals that are targeted for voluntary reduction or elimination. While the specification that outlines the sodium dichromate sealing process delineates other sealing processes (specifically, boiling deionized water and solutions containing cobalt or nickel acetate) that are approved for use, these alternatives have not been successful for all OO-ALC applications. Because the specification also allows the consideration of other, less traditional non-chromium sealers, the Air Force Research Laboratory Energy and Environment Team tasked Concurrent Technologies Corporation to identify viable alternatives to the sodium dichromate sealer, conduct testing on these alternatives, and initiate implementation of the most-promising sealer(s) based on the test results. This presentation will describe test results for several alternative non-chromium sealing technologies. Based on these results, a commercial-off-the shelf permanganate-based sealer was recommended because it can be used on both 2024 and 7075 aluminum alloys for wheels and struts processed at OO-ALC. This sealer was subsequently approved for use by OO-ALC on these materials after a thorough engineering review. OO-ALC's plans to use the new sealer will also be described.
Brush Plating of Nickel-Tungsten Alloy for Engineering Applications
Z. Zhong, S. J. Clouser, SIFCO Applied Surface Concepts, Independence, OH
Hard coating can improve the surface properties of a material beyond the capability of the substrate. For a long time, coatings such as hard nickel, hard chromium, hard alloys and hard composites have been developed for engineering applications due to the improved wear resistance. A newly-developed nickel-tungsten brush plating process has the potential as an alternative of electroplating of hard chromium for engineering application.
The nickel-tungsten solution is based on the ammoniacal citrate bath, which can be conveniently brush plated just as brush plating of other metals or alloys. On the other side, hard chromium cannot be brush plated due to the exposure of hazardous hexavalent chromium exceeding the Occupational Safety and Health Administration (OSHA) limits.
The nickel-tungsten alloy coating has been developed for engineering application. It is of nanocrystalline structure (~ 2 nm crystallite size) and demonstrates excellent hardness and wear resistance. The coating is 60% nickel, 40% tungsten by weight. Due to high tungsten content in the alloy, it is thermally stable. Moderately elevated temperatures (200 ~ 500 °C) do not cause grain size growth and softening as the case of most other hard coatings (such as hard chromium, nickel phosphorus). Actually, the nickel-tungsten alloy coating can be further hardened by exposure to high temperature of 200 ~ 500 °C for a short period of time. Beyond the hardness and wear properties, the coating has been further characterize by XRD, electronic and optical microscopy, hydrogen embrittlement, salt spray corrosion, tribology, axial fatigue, and other testing.
Computer Modeling of Induction Heating of Metals
V. Rudnev, Inductoheat Inc., Madison Heights, MI
Many of commercial codes used for computer modeling of induction heating processes are all-purpose generalized programs that were primarily developed for modeling electro-thermal processes taking place in electrical machines, motors, medical, circuit breakers, non-destructive testing, transformers, magnetic recording systems and were later adapted to induction heating needs. A necessity to sell products to as many customers as possible forces software developers to produce universal simulation tools that can be used by much larger industries compared to induction heating.
As a result, certain process subtleties related to induction heating of metals were “over-looked” by developers or substantially simplified. Regardless of well-recognized impressive capabilities of modern numerical commercial software, many of generalized programs experience difficulties in taking into consideration certain features of induction heating applications.
Presentation provides an objective assessment of a variety of generalized commercially available software for modeling of induction metal heating. It also discuses common misinterpretations, misassumptions, and errors occurred while applying some commercially available software. Case studies of computer simulations of a variety of induction heating applications will be discussed in this presentation as well.
Metallic Coating of Composite Materials
R. Freeman, M. Riley, D. Harvey, TWI Ltd, Cambridge, United Kingdom
The use of composites as structural components is increasing due to good strength to weight ratios. However their limited surface properties prevent their use in applications where thermal management, wear resistance or electrical conductivity is required e.g. aircraft engines, missile systems, helicopter blades etc. TWI has developed an advanced coating technology (CompoSurf™), employing thermal and cold spraying processes, which offers the prospect of increased functionality of composite materials. The coatings enhance the surface properties of composites to provide greater resistance to wear and erosion, corrosion, as well as providing electrically conductive (CompoStrike™ and CompoConduct™), tooling surfaces (CompoTool™) and thermal protection (CompoTherm™).
This presentation will show examples of where the coatings have been developed for specific applications, and recent advances in this exciting area.
Practical Applications of Cold Gas-Dynamic Spray
D. Wright, Accuwright Industries, Inc., Gilbert, AZ
Accuwright Industries, Inc. is a leader in Research & Development and Production applications of High and Low Pressure Cold Spray. Applying materials such as Pure Aluminum and Aluminum Alloys, Accuwright has developed and pioneered repairs for Aluminum and Magnesium housings and worn components for Aerospace and Industrial applications. We propose to describe a brief history of our developments and specific application success to share practical potential capabilities of the Cold Spray processes.
Evaluation of Cold Spray Process for Repair of Damaged ALCLAD 2024-T3 Aircraft Skin: The Advantages and Limitations
M. Yandouzi1, B. Jodoin2, S. Gaydos3, (1)Ottaw University, Ottawa, ON, Canada, (2)Ottawa University, Ottawa, ON, Canada, (3)Boeing, St. Louis, MO
Unlike thermal spray process, the recent development of cold spray technology has made possible the deposition of dense and oxide-free coatings; with good adhesion and with almost no degradation on the microstructure of the coated parts. This work will focus on the performance of using low pressure cold gas dynamic spray system (LP-CGDS) to repair damaged Alclad 2024-T3 aircraft skin. The effect of the spraying process parameters on the quality of the coating has been investigated. The optimal parameters’ of spraying commercially pure aluminum have been determined. Microstructures, microhardness, adhesion strength, surface finish and corrosion resistance were performed using different ASTM & Boeing standards.
The Forging Defense Manufacturing Consortium: Activities within Aviation
J. D. Tirpak, SCRA, Charleston, SC
The Forging Industry Association Department of Defense Manufacturing Consortium will illustrate several of its projects related to Aerospace Forgings and Aerospace Forging Supply Chains. Since our last presentation at Aeromat in Dayton 2009 the FDMC has continued to invest in a host of projects of which we will highlight progress as of 2012. The Metal and Process Optimization Project addresses the question of how to simultaneously tradeoff material and process for new or legacy systems. Often forging is competed with machining, and the optimal selection is often influenced by the combined factors of order quantity and part performance. Job Shop Lean Internships continue to produce results in forges in optimizing process flow with new algorithms and training future industrial engineers for forges. The National Forging Tooling Database continues to perform while addressing the needs of new systems which are rapidly becoming legacy systems. The FORGE-IT Team continues to reach out to Forging Designers and Buyers, and coupled, with our Modeling Team at Scientific Forming Technologies Corporation we have also addressed work force needs in forging design. The presentation will also touch upon the elusive topic of affordable, rapid tooling for forgings.
JobshopLean: A Different Lean Manufacturing Strategy for High-Variety Low-Volume Forging Suppliers in Defense Supply Chains
S. Irani, The Ohio State University, Columbus, OH
A significant number of forges (and foundries) that are DOD suppliers are high-variety low-volume (HVLV) manufacturers. While these manufacturers have reported significant benefits by adopting some of the tried-and-tested universal Lean best practices, like Visual Workplace (5S), Setup Reduction, Total Productive Maintenance, Quality At Source, Workforce Empowerment, etc., they also acknowledge getting frustrated when they begin tackling tackling the “jobshop aspects of their operations”, such as high variety of product routings, equipment monuments and batch-type processes that cannot be co-located in one-piece flow cells, scheduling using their legacy MRP systems, etc.
Inspired by this reality that many of Toyota’s methods are inappropriate for HVLV jobshop-type manufacturers, the Forging Defense Manufacturing Consortium invested in the development of a new manufacturing strategy, JobshopLean, the Nation’s only research, academic education, workforce training and industry outreach program that is specialized for small-to-medium HVLV manufacturers. This strategy was developed and deployed in forging supply chains as part of a project nested within the PRO-FAST and FAST programs funded by the Defense Logistics Agency. Over the last 10+ years, our projects have enriched and expanded the existing Lean Manufacturing programs already in place at custom forge shops (and foundries) that produce forgings and castings to sustain aging DOD weapon systems.
This presentation will summarize the spectrum of projects (facility layout, setup reduction, Office Lean, cellular manufacturing despite the existence of monuments that prevented co-location of all equipment into cells, tool and die flow management, shopfloor scheduling) that were done in a variety of forges and the tangible results that were delivered to each of those forges.
Three Decades of Metal Forming Process Simulation
J. Walters, Scientific Forming Technologies Corporation, Columbus, OH
In the late 1970’s and early 1980’s, initial applications of process simulation were reported for metal forming applications using FEM. The ALPID code was developed with funding from the US Air Force, and showed promise in a number of initial industrial applications.
Connecting the dots between early computer models and the shop floor required significant time and effort. Over the years, many contributors pushed this technology to the point where most forge shops use simulation daily. This technology has contributed directly to hundreds of millions of dollars in savings and faster process development cycles. The benefits have been compounded with of improvements in computer technology.
Today, process simulation spans multiple processes, with an eye on predicting the microstructure and mechanical properties of a finished part.
The presentation will provide an overview of the advancements made in metal forming and heat treatment process simulation. Additionally, a look at the future will be provided. This is an ongoing success story worth telling.
" Complying with Aerspace Forging and Heat Treating Standards with Regenerative Combustion Systems "
W. Tracey1, J. Dzik2, (1)Fives North American, Cleveland, OH, (2)Fives North American Combustion, Cleveland, OH
Evaluation of Near-Beta Titanium Forgeability, Heat Treat, and Testing Capabilities
L. Moody, Weber Metals, Paramount, CA
Near-beta alloys have much to offer aerospace applications, with many new alloys being developed to provide better forgeability, ductility, fracture toughness, and strength than traditional alloys. This presentation will provide an overview of near-beta alloys forgeability, heat treat response, and testing in closed die forging configurations.
Overview of New Hydraulic Radial Forging Operation at Universal Stainless’ Ohio Plant
J. Daw, Universal Stainless and Alloy Products INC, Bridgeville, PA
Universal Stainless has installed and commissioned a state of the art hydraulic radial forge ( SMX-650 / 13MN) at a greenfield site in North Jackson, Ohio. The results of initial forging trials on a number of aerospace alloys including Vacuum Arc Remelted (VAR) low alloy and stainless steels, as well as higher alloy materials will be reviewed. The open die , mechanical radial , and hydraulic radial forging processes will be compared and contrasted.
Integrated Computational Materials Engineering: Recent Progress in the Advanced Titanium Microstructure and Mechanical Properties Modeling
V. Saraf1, M. G. Glavicic2, R. R. Boyer3, T. F. Broderick4, F. Cohen5, Y. Wang6, D. Boyce7, W. T. Wu8, A. Salem9, R. A. Wallis10, V. Venkatesh11, S. L. Semiatin12, (1)ATI Ladish, Cudahy, WI, (2)Rolls-Royce Corporation, Indianapolis, IN, (3) Consultant, Issaquah, WA, (4)UTC, Beavercreek, OH, (5)Pratt & Whitney, East Hartford, CT, (6)The Ohio State University, Columbus, OH, (7)Cornell University, Ithica, NY, (8)Scientific Forming Technologies Corporation, Columbus, OH, (9)Universal Technology Corporation, Wright-Patterson AFB, OH, (10)Wyman Gordon Forgings, Inc, Houston, Texas, Houston, TX, (11)TIMET, Henderson, NV, (12)Air Force Research Laboratory, Wright-Patterson AFB, OH
Development and adaptation of predictive thermal, mechanical and microstructure models is becoming a norm in the aerospace supply chain. The USAF brought together different companies across the aerospace supply chain under the auspices of the Metals Affordability Initiative (MAI) to develop, validate and integrate the predictive models for wrought titanium alloys. Thus, creating a true Integrated Computational Materials Engineering (ICME) story.
In this ICME program, various computational models were developed and validated that predict location specific microstructure and mechanical properties for wrought titanium alloys. Developed models such as phase field, crystal plasticity, variant selection, thermodynamic and artificial neural network models will be integrated to help design the manufacturing process for Ti6-4 components yielding desired properties. Program results and integration plan will be discussed with the emphasis on the end-goal of training the artificial neural network that can predict mechanical properties for Ti6-4 components based on chemistry, microstructure and crystallographic texture.
Solution Heat-Treatment of the Nb-Modified MAR-M247 Superalloy
P. R. S. A. e Silva, R. Baldan, G. C. Coelho, A. M. S. Costa, C. A. Nunes, The University of Sao Paulo , Lorena, Sao Paulo, Brazil
MAR-M247 superalloy has excellent mechanical and oxidation/corrosion properties at elevated temperatures. Niobium is a refractory element normally present in the composition of nickel-based superalloys, found mainly in γ’ phase and MC carbides [1]. In general, solution heat-treatments are applied before an aging heat-treatment. The objectives of these treatments is to dissolve the γ’ phase in γ matrix and minimize segregation from non-equilibrium solidification, in order to produce a γ’ controlled re-precipitation during aging heat-treatment, an uniform and isotropic material with better properties [2,3]. The aim of this work was to find the best condition for solution heat-treatment of a MAR-M247 modified Ni-base superalloy through microstructural characterization of as-cast and heat-treated materials, comparing the results with experiments of differential thermal analysis (DTA) and Thermocalc simulations.
The conventional MAR-M247 superalloy was modified by replacing the amount of tantalum by niobium (in atomic %) and then the nominal composition of Nb-modified MAR-M247 superalloy is: 10.2 wt % Co, 10.2W, 8.5Cr, 5.6Al, 1.6Nb, 1.4Hf, 1.1Ti, 0.7Mo, 0.15C, 0.06Zr, 0.015B, Ni balance. This superalloy was produced in a vacuum induction melting furnace (VIM) via investment casting (lost-wax technique) at Açotécnica (Jandira, São Paulo, Brazil).
The samples selected to solution heat-treatments were encapsulated in quartz tube in argon atmosphere and heat-treated in a ceramic tube furnace with MoSi2 resistive element followed by air cooling. The samples were heat-treated at 1185, 1240, 1260, 1280 and 1300 oC for times of 2, 4 and 8 hours. The as-cast and heat-treated samples were prepared following conventional metallographic techniques, etched with a glyceregia solution and characterized in conventional SEM and FEG-SEM, both with EDS detector. All samples were submitted to microhardness measurements.
According to Thermocalc simulations, the window of solution heat-treatment for MAR-M247(Nb) superalloy is between 1212 oC (γ’ solvus temperature) and 1315 oC (solidus temperature). Besides, in DTA experiments, the γ’ solvus temperature was 1238 oC and the incipient melting temperature was 1281 oC, limiting temperature of heat-treatment because segregation. The sample heat-treated at 1280 oC showed incipient melting. Therefore, Thermocalc simulations have shown a good agreement with DTA experiments.
Characterization of Rafting and its Influence on TMF
M. M. Kirka1, R. A. Kupkovits2, R. W. Neu1, (1)Georgia Institute of Technology, Atlanta, GA, (2)Exponent Failure Analysis Associates, Los Angeles, CA
In thermomechanical fatigue (TMF) testing and life prediction of Ni-base superalloys used in gas turbine engines, the evolution of the two phase γ-γ’ microstructure is often neglected. During service, the turbine components form gradients of aged microstructures that are dependent on the localized temperature and stress state. In the case of Ni-base superalloys, the aged microstructures are of the form of coarsened γ’ precipitates with morphological changes called rafting. These changes in microstructure have been shown to influence both the stress-strain and TMF behavior.
Prior work has attempted to address whether γ-γ’ rafting is damaging or in some special cases advantageous, and also to see if this behavior can be avoided through further optimization of the initial microstructure constituents. While most of these attempts have been unsuccessful, it is now commonly understood that rafting can lead to creep acceleration and a reduction in creep strength, although these are not mutually exclusive, and is therefore important to include in a holistic life prediction methodology.
This study is aimed at developing structure-property relationships based on rafting experiments. One of the end goals is to develop a microstructure-sensitive constitutive model that captures how changes in microstructure from coarsening and rafting influence the mechanical behavior, including the temperature dependence on the yield and hardening response as well as TMF, so that these influences can be readily predicted in the design and life analysis of hot section components. This paper focuses on the experimental characterization and observations in a particular directionally-solidified (DS) Ni-base superalloy.
Special axial fatigue specimens were designed to facilitate pre-rafting through placement in a creep frame. Compared to virgin samples, specimens whose γ-γ’ microstructure had been rafted normal to the stress axis under relative short-term creep conditions exhibited an increased yield strength by a factor of 1.2 at temperatures below 700°C and a reduced strength above. The opposite effect was observed for rafts lying parallel to the stress axis. When the tensile rafting conditions are more severe, for example a 300hr creep exposure, the yield strength is reduced.
Fractured Surface of An INCONEL 713 Superalloy Turbine Blade
N. Boutarek1, M. A. Acheheb2, (1)University of Science and Technology, Algiers, Algeria, (2)bLaboratoire de Science et Génie de Métallurgie LSG2M, Ecole des Mines de Nancy,, Nancy, France
This study focuses on the characterization and examination of the fracture mechanisms acting simultaneously on the fractured surface of a nickel-based Inconel 713 superalloy gas turbine blade. This objective is reached using a variety of experimental approaches to determine the material's properties (chemical composition, morphology and crystalline structure) and the microscopic observation of the fractured surface. Major morphological variations are observed (microfacets, microcupules and streaks). Correlations have been established leading to the conclusion that three competing fracture mechanisms are involved. The main fracture mechanism is intergranular thermo-mechanical fatigue starting at the border of the blade. However, intragranular fracture by stress corrosion under load, and intergranular fracture by creep are also operative simultaneously in the center of the observed surface. Various explanations for the premature fracture behaviour of the turbine blade are discussed.
A Study of the Effects of Ta and Y in the Microstructure and Oxidation of MCrAlY Based Bond Coating Alloys
E. Karagianni, P. Tsakiropoulos, The University of Sheffield, S1 3JD, United Kingdom
Ni based superalloys in power plants operating with a wide range of fuels using combined cycle power plant technologies require protection for high temperature oxidation and type I and type II hot corrosion. MCrAlY overlay coatings are environmental protection coatings that can provide an optimised corrosion response over a wide range of turbine operating conditions that are likely to be encountered in utility turbines, working with multi-fuel capability. In this study we have concentrated on Co and Cr rich, Ni-Co-Cr-Al based bond coat type alloys. We shall report on the effects of Ta and Y individually and simultaneously in the as cast and heat treated (1200 ºC/ 100 h, 200h) microstructures and oxidation behaviour of Ni-23Co-20Cr-8.5Al (wt%) based alloys. The paper shall discuss phase formation and stability with particular emphasis on solidification path and composition of phases. The oxidation behaviour of the alloys at 975 ºC will also be compared.
Crack Growth Behaviour of An Advanced Nickel Disc Alloy Under Thermo-Mechanical Fatigue Conditions
M. Lunt1, S. Stekovic2, S. Jacques3, L. Waterhouse4, A. Wisbey3, (1)DSTL, Salisbury, United Kingdom, (2)Rolls-Royce plc, Derby, United Kingdom, (3)Serco Technical Services, Warrington, United Kingdom, (4)Serco Technical Consulting Services, Warrington, United Kingdom
The increasing operating temperature of aerospace gas turbines is beginning to result in the fracture critical discs experiencing new combinations of thermal and mechanical stresses during operation of new engine designs. This change is leading the disc material to encounter thermo-mechanical fatigue conditions more and has required the development of improved life prediction methods to account for this change in operating conditions.
To assist in the validation of the life prediction methods and to enable a better physical understanding of the crack growth behaviour under thermo-mechanical fatigue conditions to be obtained a facility has been recently commissioned to specifically enable crack growth measurements under representative conditions. This paper very briefly reviews the development of this test facility.
The initial tests have been performed on the advanced nickel disc alloy, RR1000 in two microstructural conditions. Thus the temperature has been cycled between 400oC and 700oC, whilst a simplified load cycle has also been applied. The fatigue crack growth rate measurements have demonstrated a significant benefit from the use of a large grain size microstructure, compared with the conventional fine grain structure. The fracture path and underlying microstructural features have been examined and correlated with the change in crack growth rates.
Effect of y' size on Strain Localization at Micro-Scale in Nickel-Base Superalloy RR1000
P. Enderson, M. Preuss, J. Quinta da Fonseca, University of Manchester, Manchester, United Kingdom
Polycrystalline nickel base superalloys used for turbine disc applications are being required to operate at higher thermal and mechanical stresses due to the efficiency gained from increasing turbine entry temperatures. The performance of these materials relies heavily upon the strengthening gained from the ordered phase Ni3Al (y’). In order for the mechanical properties of these materials to be optimised, it is key to improve our fundamental understanding of the effect of y’ size and its distribution on the deformation mechanisms and deformation characteristics. Fatigue resistance is an important requirement for these materials. In single crystal alloys, fatigue failure has been linked to deformation localization. Recent work [1] has suggested that the degree of localization is influenced by y’ size, which has important implications for the fatigue resistance of these alloys. The aim of this work is to quantify the level of strain localization, at the microstructural scale, in samples of polycrystalline disc alloy RR1000 with different y’ sizes.
Recent developments [2] have made it possible to map strain localisation with sub-micron resolution using digital image correlation (DIC) of images acquired with an electron microscope. DIC is a computational image analysis technique, which allows the calculation of in-plane strains at different stages during deformation from changes in a pattern deposited on the sample surface.
The results indicate that the fine y’ microstructure shows significant amounts of strain localization which is displayed by the presence of very defined slip bands caused by y’ shearing. The coarse y’ microstructure however, displays far more homogeneous deformation with no apparent y’ shearing. Electron backscatter diffraction was then used to determine the relationship between slip bands and crystallographic orientations. Although the majority of slip bands are aligned with {111} slip traces, a significant amount are not. Furthermore, the degree of strain localization does not seem to be related to the Schmid factor calculated by resolving the macroscopic applied stress along the likely slip direction.
Elemental Effects on Nickel Base Superalloy Powders
A. Banik1, T. Gabb2, B. McTiernan3, (1)ATI Allvac, Monroe, NC, (2)NASA Glenn Research Center, Cleveland, OH, (3)ATI Power Metals, PITTSBURGH, PA
The interest in powder metal superalloys has continued to grow since the 1960’s with the development of the Gatorizing process. As a result, the processing of powder metal superalloys has evolved into a combination of special compositions and process routes based on the mechanical property constraints of the application. Typically, powder metal alloys utilized high gamma prime forming compositions to accommodate the high turbine inlet temperatures in combination with high carbon and boron compositions to control grain growth and creep resistance. As the applications of powder metal superalloys expand, compositions tailored to meet specific property requirements in the bore and rim of components are being developed. Elemental considerations relative to superalloy powder processing, material costs and the effect on superalloy properties will be discussed.
Role of Precipitates Statistics on Intergranular Crack Growth in Ni-Based Superalloys
K. Maciejewski, H. Ghonem, University of Rhode Island, Kingston, RI
This paper examines the role of microstructure, in particular, the size and volume fraction of secondary and tertiary γ’ precipitates, on intergranular crack growth in P/M IN100. Heat treatments have been carried out on the material in order to control the γ’ statistics. Dwell fatigue crack growth experiments were performed on different microstructures at 650°C, resulting in variations of crack growth rate (CGR) by one order of magnitude. CGR is shown to decrease with an increase in yield strength. This is discussed in terms of the hardening behavior of the continuum surrounding the grain boundary (GB) and its effect on the opening displacement rate during the intergraular cracking process. This trend was further investigated by considering the individual contributions of solid solution, γ’s and γ’t to the total yield strength. For this, the hardening contribution of the γ’ to the yield considers dislocation/precipitate interactions involving particle shearing and/or Orowan by-passing mechanisms. Results of the CG tests indicated that both the γ’s and γ’t yield components are inversely proportional to CGR. Additionally, there was a higher dependency of the γ’t yield component in relation to CGR and yield, indicating that γ’t would indirectly play a role in intergranular cracking. Thus, conditions where the γ’t are unstable, such as dissolution, could lead to an increase in CGR. This has been studied in ME3 alloy at 760°C, where the γ’t particles near the GB crack path have shown evidence of dissolution resulting in a transient microstructure and variations in CGR.
An Update on Technical Development and Implementation of ATI 718Plus Alloy
E. T. McDevitt, Allegheny Technologies Incorporated (ATI), Monroe, NC
ATI 718Plus® alloy is a cast and wrought Ni-base superalloy developed in the early 2000’s to bridge the gap in temperature capability between alloys 718 and Waspaloy. At the Superalloys 718, 625, 706 and Derivatives 2005 conference, ATI presented several papers on the development and performance of the alloy in multiple product forms. Since that time, ATI 718Plus alloy has been fully commercialized and is being inserted into gas turbine engines. Furthermore, the manufacturing characteristics and the mechanical properties have been more thoroughly characterized. This presentation will review the progress to date in characterizing the mechanical properties and performance of ATI 718Plus alloy as well as discuss applications and new product forms currently under development.
Characterization of H-282 Forged Seamless Rings
O. Covarrubias, Frisa Forjados SA de CV, Santa Catarina, Mexico
Haynes H-282 alloy is a new gamma-prime strengthened superalloy developed for high temperature structural applications. This superalloy can develop an interesting combination of creep strength, thermal stability, weldability and fabricability. Such properties and expected operational temperature range of 649 to 927C, make this material suitable for the fabrication of seamless rings with application in aircraft engines.
In this paper, microstructural and mechanical characteristics of H-282 superalloy are evaluated when seamless rings are produced considering industrial conditions. Effect of variables as hot-working temperature, deformation ratio and heat-treating are evaluated in characteristics as microstructure, tensile and stress-rupture testing. Scanning electron microscopy complements microstructural evaluation.
Batch Uniformity Proved by Means of Electrical Conductivity Measurement Influenced by Solution Heat Treatment Only?
C. Henkel1, R. Rachlitz1, H. Böttcher2, (1)AMAG rolling, Ranshofen, Austria, (2)AMAG Casting, Ranshofen, Austria
The batch uniformity of aircraft plates has to be proven by means of electrical conductivity measurements. The absolute value is influenced by the solution heat treatment as well as the natural and / or artificial aging. The difference value is normally controlled by the quench conditions after solution heat treatment. Sporadically, in 7075 plates in temper T7351 conductivity differences of up to 1.5 MS/m occurred, i.e. above the tolerance limit, so that the plates had to be scraped.
The mechanical properties are not affected by these conductivity differences. At the first root cause analysis solution heat treatment variations could be excluded too. In the following the whole process chain was investigated systematically, beginning with the chemical composition of the ingot up to the artificial aging of the final plates.
The investigations proved that the conductivity differences were caused by Cr-precipitations, which arise in an early stage of the production and cannot be solved afterwards.
The Microstructure Evolution of Semi Solid AM80 Alloy Added Zr and Its Compression Behavior At Elevated Temperature
B. H. Seong, H. K. Kim, G. H. Van, S. G. Lim, Gyeongsang national university, jinju, South Korea
In this research, the effect of Zr addition on the microstructure of semi solid AM80 alloy by cooling plate was investigated and compression test on the alloys at elevated temperature was performed. First, in order to catch the semi-solid temperature range of Zr added AM80 alloy, a natural cooling experiment was conducted to acquire the cooling curve of Zr added AM80 alloy. Second, the microstructure observation by Optical scope (OM), scanning electron scope (SEM) and energy dispersion spectroscopy (EDS) was carried out to confirm the formed phase and change of its morphology in the alloy during elevated temperature. Third, compression test was carried out under deformation temperature range from 300 to 440oC, in present study. After natural cooling, its cooling curve with a liquidus temperature of 603oC and solidus temperature of 435oC can be obtained.
Aleris High Performance Aluminium Alloys for Innovative Solutions to the Aerospace Industry
S. Spangel, A. Buerger, Aleris Aluminum Koblenz GmbH, Koblenz, Germany
Today’s main requirements to the aircraft industry are higher fuel efficiency, lower manufacturing costs and reduced down time for inspection and repair of their aircrafts. To meet these targets and to compete against other materials such as fiber reinforced composites Aleris has developed new plate and sheet alloys designed for optimum performance while considering new manufacturing techniques and a fast ramp-up scenario.
Within Aleris focus was placed in the past years on the development of new 7xxx and thermally stable 5xxx sheet and plate alloys allowing for a superior strength toughness balance and low weight solutions.
With a density in the range of today’s Al-Lithium alloys, their excellent fatigue and damage tolerance properties, good corrosion resistance, very good weldability and robust processing route, AlMgSc alloys offer huge benefits in terms of weight and cost savings.
In addition Aleris is working on 7xxx plate products for use in wing components such as wing covers, spars, or ribs or for use in integral structures.
This paper will provide an overview of new, improved sheet and plate alloys for various aircraft applications and cost efficient processing routes based on advanced manufacturing techniques. Future developments in the field of new aerospace alloys will be highlighted.
Advances in the Development of Plate Products for Lower Wing Applications
B. H. Bodily1, L. M. Karabin2, J. Witters3, (1)Alcoa, Everett, WA, (2)Alcoa, Alcoa Center, PA, (3)Alcoa Inc, Bettendorf, IA
Al-Li-Cu-Mg alloy/products, with and without Ag additions provide substantial performance advantages over conventional 2xxx products. For lower wing applications, the combination of specific ultimate tensile strength and plane stress fracture toughness is of particular importance and this is an area in which the Al-Li alloys can excel. Corrosion resistance is an area that has received attention since it can impact inspection intervals. In this presentation, the microstructures and properties of two new alloy/products aimed for lower wing applications,
2199-T86 and 2060-T8E86, will be reviewed and compared with conventional non-Li 2xxx products. The state of maturity in terms of temper registration, AMS and design allowables is examined in detail. It is concluded that the performance improvements of Al-Li alloys/products in addition to their lower density should enable significant weight savings in modern aircraft.
New Forged Products from Alcoa
D. Bush1, C. Yanar1, A. Morris2, E. Colvin1, (1)Alcoa Forged Products, AFE, Cleveland, OH, (2)Alcoa Inc, Birmingham, United Kingdom
Development of Al-Li forged products has been a goal contemplated since the early 80s. Early alloys such as 2090 forgings exhibited low strength and toughness. 8090 products on the other hand included cold working prior to aging and were successfully implemented into the EH-101 helicopter, among other applications. In Russia, forged products from alloy O1420 gained some acceptance. This paper describes the technical aspects involved in legacy Al-Li forged products and describes the forging design challenges overcome for the development of successful forging applications. The performance of three new forging alloys termed C99N, C14U (2060) and C77W is presented and discussed in terms of the achieved mechanical properties that dictate positive performance as compared to alloys such as 7050-T74(52).
Strength Properties of Alumina Fiber Reinforced Aluminium Matrix Composites at Elevated Temperature
J. Kaczmar1, K. Naplocha1, J. Morgiel2, K. Granat1, (1)Wroclaw University of Technology, Wroclaw, Poland, (2)Polish Academy of Sciences, Krakow, Poland
The influence of fibre volume and temperature on tensile, bending and compression strength of short planar randomly distributed fibre reinforced AC 44200 aluminium alloy matrix has been tested and analyzed. First, porous (80-90%) alumina Saffil fibre preforms characterized proper permeability and strength were prepared for infiltration with molten metal. Using direct squeeze casting method, with pressure 100MPa, composite materials were produced. Microstructure observations revealed good interface between fiber and matrix, without chemical reaction products and typical in such systems spinel MgAl2O4. Though, after preparation of preform, when silica binder were used thin, 70-100nm homogenous layer of amorphous SiO2 coated fibers. Distinct improvement of strength properties with increase of fibre content was observed. At 20 vol.% of fibre increase of tensile, bending and compression strength amounted ca. 60%, 50% and 30% correspondingly. At higher temperature (200-300°C) all tested properties decreased to the level of strength of unreinforced matrix at ambient temperature.
Mechanical Characterization of Aluminum-Lithium Alloy 2050 for Space Structure Applications
J. Blacker1, J. Bowers2, M. Domack3, R. Hafley3, B. Stocking1, (1)Touchstone Research Laboratory, Triadelphia, WV, (2)Constellium Rolled Products, Ravenswood, WV, (3)NASA Langley Research Center, Hampton, VA
Aluminum-Lithium (Al-Li) Alloy 2050, manufactured by Constellium, is a promising new material that could replace the legacy alloy, Al-Li 2195, for many space structure applications. The availability of 2050 in plate gauges up to 6 inches thick provides a distinct advantage over 2195, which is limited in thickness to 2 inches, thereby enabling the design of lighter weight structures. The current efforts have resulted in an initial microstructure/property characterization of 4 inch 2050 plate, which includes tension, compression, and fracture toughness testing at room and cryogenic temperatures, as well as metallurgical evaluation. The results show that alloy 2050 has promising mechanical properties for space structure applications, which warrants further development of this alloy.
Development of Structural Plate for Aircraft Internal Structure
J. Boselli1, B. De Mestral2, J. Witters3, G. Venema4, A. Morris5, D. Humphreys5, G. Feyen5, (1)Alcoa Incorporated, Alcoa Center, PA, (2)Alcoa, Geneva, Switzerland, (3)Alcoa Inc, Battendorf, IA, (4)Alcoa Inc, Riverdale, IA, (5)Alcoa Inc, Birmingham, United Kingdom
A significant weight of "thick" aluminum plate products is used in the manufacture of an aircraft's internal structure in applications such as ribs, spars, frames, bulkheads, etc. With the recent launch of more fuel efficient and primarily metallic single aisle aircraft but also the introduction of composite-intensive twin-aisle aircraft, a number of opportunities exist for upgrading alloys developed more than 30 years ago with a new generation of Al-based products. These include 7xxx aluminum thick plate products (7085, C85T) that show significant improvements in both strength and toughness along with Al-Li products (C77W, C14U) that show high strength, low density and very high corrosion resistance with significantly improved toughness over previous generation products. Property improvements are reviewed in terms of metallurgical enablers, such as lower quench sensitivity, along with predicted structural gains (weight savings, lower maintenance) for typical applications. Development status and timelines for commercialization are also presented.
Fatigue Endurance of Al-Cu-Li Alloys
J. C. Ehrstrom, Constellium LLC, Voreppe, France
Al-Cu-Li alloys show a considerably improved fatigue resistance compared to conventional aerospace alloys, particularly those showing the same strength level. This has been demonstrated in open hole fatigue tests, in high load transfer fatigue specimens, and in notch fatigue specimens that have been subjected to surface treatment. The effect is maintained when specimens are subjected to variable amplitude loading. The origin of this improvement is not yet clear and is the subject of this paper.
The present work examines the early stages of crack initiation and growth using optical microscopy, scanning electron microscopy and eddy current local defect detection. A reference 7050 T74 alloy is compared to an Al-Cu-Li, AIRWARETM 2050 alloy, using open hole specimens. Initiation sites are identified as a function of stress level.
The results show that constituent particles are the main initiation site. Less expected is the fact that slip bands are more common as initiation sites at low stress level.
A micro-crack growth model is fitted to the observations mentioned above, using in particular the inter-striation distance. This model is then included in a statistical model for fatigue life prediction based on the distribution of constituent particles. This allows merging the data from both alloys in a consistent data set. The conclusion obtained from the modeling is that both the constituent distribution and the short crack growth rate contribute to the better behavior of AIRWARE 2050 versus 7050. However the latter effect is larger.
The model can be used as a tool to predict the effect of alloy modifications.
The Evolution of Plate Products for Upper Wing Applications
G. Venema1, D. Denzer2, B. Bodily3, J. Witters4, (1)Alcoa Inc, Riverdale, IA, (2)Alcoa Inc, Alcoa Technical Center, PA, (3)Alcoa Incorporated, Alcoa Center, PA, (4)Alcoa Inc, Battendorf, IA
High specific ultimate strength and high plane stress fracture toughness are primary requirements of aircraft fuselage skins. The performance of alloys/products used in high performance fuselage applications is first reviewed. The specific fracture toughness for products such as 2017-T3, 2024-T3, 2524-T3 and 6013-T6, is discussed as a function of their composition and microstructure. Then the performance of modern Al-Li alloys/products such as 2199 and 2060 sheet and 2099 and C99N extrusions is examined. It is concluded that the performance of Li containing alloys/products offer significant improvements over non-Li containing conventional fuselage products because of the optimization of strengthening precipitates and grain microstructures. The role of chemical composition and processing on resulting microstructures is discussed.
New Fuselage Sheet Products for Medium Size and Llarge Aircraft
D. Mooy1, P. Magnusen2, B. H. Bodily3, R. Kane2, J. Witters1, (1)Alcoa Inc, Battendorf, IA, (2)Alcoa, Inc., Alcoa Center, PA, (3)Alcoa, Everett, WA
Whenever a new plate or sheet product for fuselage or wing applications is developed, a companion extruded product needs to be developed in parallel. This is to optimize the performance of the structural (extrusion combined with flat rolled product) component. This presentation highlights the evolution of extruded products for use in aircraft construction. Particularly the performance of the latest extruded products from Alcoa is highlighted. Product characteristics and state of maturity towards temper and AMS registration is discussed in detail
An Integrated Approach to Manage the Impact of Bulk Residual Stress On the Design-Build-Sustain Process for Primary Aircraft Structure
M. A. James, J. D. Watton, M. Newborn, B. Schultz, R. J. Bucci, Alcoa, Inc., Alcoa Center, PA
Integrated product development teams and computational methods have received significant attention in recent years as a means to accelerate new material insertion and reduce cost in the product development cycle. When combined, they form the basis for the field of Integrated Computational Materials Engineering (ICME), which is held up as an enabler for the community with benefits ranging from material design through component design, manufacturing, and even sustainment. Alcoa has for many years used ICME as part of the product design process, and during that time, substantial progress has been made towards solving myriad complex technical challenges associated with forged part design. Recently, under the Metals Affordability Initiative (MAI), the Air Force provided opportunity for stakeholder companies to join forces to develop and validate computational capabilities necessary to integrate bulk residual stress into the design and manufacture of forged, aluminum-alloy, primary aircraft structure. The presentation discusses advances in residual stress modeling achieved during the last several years, summarizes recent residual stress measurements that are part of the validation plan, and outlines the path forward via the MAI program. The preliminary results affirm that more than ever, knowledge of residual stress influences on design and manufacturing processes is essential to both assure conservatism and maximize performance.
Optimization of Stiffened Panels Using Element Free Galerkin Method and Kriging Model
A. Yeilaghi Tamijani, S. B. Mulani, R. K. Kapania, Virginia Polytechnic Institute and State University, Blacksburg, VA
A framework is developed for structural optimization using Element Free Galerkin (EFG) method, kriging method and Genetic Algorithm (GA). The element free Galerkin method is used to evaluate the objective function at the sample points used for developing the surrogate model for estimating the function value in design optimization. Kriging method is used to develop a surrogate model and a genetic algorithm is used as a global optimizer. The framework is tested for a plate with curvilinear stiffeners. The efficiency and the accuracy of the framework is compared with two other approaches: 1) MD.PATRAN®, MD.NASTRAN® and VisualDOC® as implemented in EBF3PanelOpt, a Computational Design Environment being developed at Virginia Tech to optimally design panels with curvilinear stiffeners, and 2) kriging, MD.PATRAN® and MD.NASTRAN® (using EBF3PanelOpt) and genetic algorithm. All approaches use optimization methods on both the shape and size design variables. The optimization scheme is a two-step optimization approach by dividing the design variable into size and shape variables. First the buckling parameter is maximized over the shape design variable and then mass is minimized over the size variable with constraint on buckling. The comparison between three approaches shows the efficiency and accuracy of the developed framework. It was shown that by using meshfree method, the curvilinearly stiffener geometry and nodes are regenerated for each design point analysis while plate geometry and mesh can be kept unchanged during optimization which results in significant reduction in CPU time.
EBF3PanelOpt: An Overview and Recent Developments of An Optimization Framework for Stiffened Panel Using Curvilinear Stiffeners
S. B. Mulani, R. K. Kapania, Virginia Polytechnic Institute and State University, Blacksburg, VA
For the last four years, an optimization framework, EBF3PanelOpt, is being developed to design panels with curvilinear stiffeners so as to utilize the larger design space made possible by direct digital manufacturing that uses additive manufacturing techniques like the Electron Beam Free Form Fabrication, Friction Stir Welding, and Selective Laser Sintering. Structural loads of future aerospace vehicles may not be well characterized using current knowledge-based databases, so medium-fidelity software like Msc.Patran (geometry modeling and mesh generation), Msc.Nastran (Finite Element Analysis) are integrated in EBF3PanelOpt framework using the Python programming environment. Earlier version of the EBF3PanelOpt supported curvilinear blade stiffeners without loads acting through the stiffeners to optimize the panels for minimum mass subjected to buckling, von Mises stress, and crippling or local failure of the stiffener constraints. EBF3PanelOpt is enhanced to have curvilinear T and L stiffeners with or without axial loads in addition to the loads acting only on the panel. The panel/stiffener geometry is defined in a parametric fashion based on design variables that include variables for orientation and shape of the stiffeners. This framework is modified to support a coarse-grained parallelism to analyze multiple designs on the cluster. This framework can easily be coupled with any optimizer like VisualDOC, DAKOTA or MATLAB. A vertical stabilizer skin panel of transport aircraft panel having two extreme load-cases, is optimized using with or without stiffener loads. The optimization results are compared with the current industry practice leading to a 17% reduction in the panel mass for an example panel.
Optimal Supersonic Wing Structure Design Using Curvilinear Spars and Ribs (SpaRibs)
D. Locatelli, S. B. Mulani, Q. Liu, R. K. Kapania, Virginia Polytechnic Institute and State University, Blacksburg, VA
Supersonic aircraft design is characterized by major interactions among different disciplines: namely, structures, aerodynamics, thermal effects and flight dynamics. Hence, designing such aircraft requires severe constraints or requirements on the static and dynamic behavior of the structure. These requirements can only be met with the implementation of innovative design concepts during the early design phase. This research illustrates how the use of curvilinear spars and ribs, SpaRibs, can be advantageous for designing supersonic transport aircrafts. The primary benefit of using curvilinear stiffening members in the fabrication of wing-box structures is the coupling between bending and torsion deformations which provides a more efficient load-bearing mechanism. Moreover, the use of SpaRibs provides an enlarged and more flexible design space as compared to conventional design concepts. The mathematical parameterization used to describe the geometry of the SpaRibs is presented. In particular, the shape of the stiffening members is defined using third-order B-splines. The SpaRibs concept is applied to the design optimization of a supersonic transport aircraft. Aerodynamic loads are computed for critical maneuvers using doublet-lattice and ZONA51 methods implemented in MSC.NASTRAN. Static and buckling analyses are subsequently performed to check for maximum stress and instability constraints. Divergence and flutter velocities are also computed using MSC.NASTRAN and included as constraints of the design. A comprehensive set of results is presented, showing the optimum configuration using SpaRibs, the stresses, and the deformation of the structure under computed flight loads and the aircraft flutter envelope.
Light Weight For Today’s and Future Metallic Airframes: an Update on AIRWARETM Developments and Applications
F. Eberl1, T. Warner2, A. Danielou2, (1)Constellium LLC, Issoire Cedex, France, (2)Alcan, Voreppe, France
Within the today’s challenges for competitive commercial aircraft, as reduced environmental impact, reduced operating cost and more comfort for the passengers, the right material choices play a key role.
Concerning the reduced environmental impact, the optimized structural weight to reduce fuel consumption is fundamental. Close collaborations between material supplier and airframer allow to optimize design by using lightweight technologies as AIRWARETM. In complement to the lightweight structure, the full life cycle of the airframe needs to be taken into account, from the fabrication up to the dismantling of the aircraft structure, in particular for commercial aircraft programs lasting at least 30 years. The AIRWARETM low density alloys allow a 100% recycling loop, minimizing the environmental footprint. Also from a cost point of view, the full recycling loop has great interest for the customer. In close customer collaborations, win-win situations can be generated for the supplier and the airframer for competitive business cases.
Recent commercial aircraft programs as Airbus A350XWB and Bombardier CSeries selected the AIRWARETM technology for primary structure parts. Metal quantities per airframe became significant, so that investments were needed to respond to the market needs. Constellium switched from an industrial ingot by ingot technology to a full size industrial AIRWARETM cast house technology. The step change of technology allows further acceleration of future developments in order to further face the today’s market challenges.
From an intrinsic AIRWARETM alloy properties point of view, AIRWARETM shows step change improvements in fatigue, corrosion and easiness in assembly, in particular friction stir welding (FSW). These characteristics are still exploited only partially, so that AIRWARETM technology is only in the beginning of future airframe improvements.
An overview of Constellium‘s AIRWARETM technology will be presented including its use in advanced assembly concepts. Comparisons to today’s flying structures will be mentioned as baseline in order to better appreciate the step-change which has been made in the last decade.
The Evolution of Extruded Products for Use in Aerospace
L. Yocum1, D. Denzer2, E. Colvin3, (1)Alcoa Forgings & Extrusions, Lafayette, IN, (2)Alcoa Inc, Alcoa Technical Center, PA, (3)Alcoa Inc, Lafayette, IN
The progression of upper wing product improvements achieved through the development of alloys that include 7075-(T651 & T7651), 7150-(T6151 &
T7751) and 7x55-(T7751 & T7951) is reviewed. The most current advancements include aluminum-lithium plate and extruded products that can attain strength equivalent to that of 7055-T7751 with higher modulus, similar fracture toughness and improved fatigue, fatigue crack growth and corrosion performance. The state of development of a new class of high strength Al-Li alloys is reviewed in detail. The improved fatigue performance of these products is highlighted. Trade studies showing the benefit in terms of weight savings and durability using advanced products and advanced design considerations are discussed.
The Development and Validation of New Thermodynamic and Mobility Databases for Aluminum Alloys
P. Mason1, A. Markstrom2, Y. Du3, S. H. Liu3, J. L. Zhang3, L. Kjellqvist2, J. Bratberg2, A. Engstrom2, Q. Chen2, (1)Thermo-Calc Software Inc., McMurray, PA, (2)Thermo-Calc Software AB, Stockholm, Sweden, (3)Central South University, Changsha, Hunan, China
CALPHAD based tools are an integral component of ICME in terms of predicting the underlying thermodynamics of multicomponent alloys of industrial importance, the phases formed , their sensitivity to compositional variation and temperature, phase transformations, soldification behavior and microstructure evolution. Such tools are useful both from an alloy design perspective while also improving understanding of existing alloys, and process optimization.
The CALPHAD approach relies on the capability to provide fundamental phase equilibrium and phase transformation information, which is possible due to the adopted methodology where free energy or atomic mobility of each phase in a multicomponent system is modeled hierarchically from lower-order systems, and model parameters are evaluated by considering ab-initio and various experimental data.
For more than fifteen years CALPHAD has been applied successfully within the aluminium industry, but to maximize the benefits of ICME requires further development of both software and databases; databases which cover broader ranges of composition for example. With ongoing research and development into new aluminum alloys for the aerospace market, with the drive towards lower density, higher performance alloys, databases need to be developed which take these requirements into account.
Presented here is a new thermodynamic database, and a corresponding mobility database for Al- alloys based on the critical evaluation of all the constituent binary systems across their full range of composition, 59 ternaries, 15 quaternaries and 1 quinary. This database contains all the important Al- alloy phases within a 26-element framework [Al-Cu-Fe-Mg-Mn-Ni-Si-Zn-B-C-Cr-Ge-Sn-Sr-Ti-V-Zr-Ag-Ca-H-Hf-K-La-Li-Na-Sc] and in total 345 solution and intermetallic phases are included
On the Prediction of Machining-Induced Distortion in Forged Aerospace Components
S. Ayvar, M. Thomas, P. Osborne, S. Turner, Advanced Manufacturing Research Centre with Boeing, Rotherham, United Kingdom
Residual stresses introduced during the primary processing of aerospace components can lead to distortion during down-stream machining operations. Such distortion can be problematic from a manufacturing perspective in achieving the stringent dimensional tolerances required within the aerospace industry. Efforts to predict the resulting distortion during roughing and semi-finishing machining operations are therefore necessary to develop mitigation strategies to minimise part distortion and maximise right-first-time components.
In this study, the suitability of the finite element code DEFORMTM-2D/3D for predicting the machining distortion in residually stressed components was assessed. A residual stress model for a condition of supply forging was validated through the hole drilling method. Machining distortion simulations were performed for the roughing and semi-finishing operations on front cover plate components with predicted distortions compared against probing data collected during experimental machining trials. The general trend of distortion as predicted by the finite element code is comparable with the experimental data, although the magnitudes of the distortions are inconsistent. Two strategies were investigated in order to compare the predicted distortions with the experimental data, and a preliminary sensitivity analysis was undertaken to identify the key variables that influence the predicted distortion.
BlueArc ™ Machining - A High Speed Roughing for Aerospace Alloys
A. L. Trimmer, S. R. Hayashi, B. Wei, General Electric Global Research Center, Niskayuna, NY
BlueArc™ is a High Speed Electro Erosion (HSEE) process that was developed to rough cut high strength aerospace alloys. Fundamentally, BlueArc™ is a controlled thermal removal process driven by an electrical potential between a tool electrode and a workpiece. Thermal events are more intense and widespread than conventional EDM processes and are controlled by the applied potential and current, the electrolyte, and the distance between the tool electrode and workpiece. Each thermal event erodes some of the workpiece resulting in bulk material removal. Under most conditions the contact forces between the electrode and the workpiece surfaces are negligible enabling the use of slender electrodes or light duty machines. End milling, peripheral machining, and shaped electrode profile machining have been studied. Machining results will be shared for nickel based superalloy and titanium alloy rough machining. In each case material removal rates 2-3 times the conventional analog for similar size tooling was achieved. BlueArc™ is a versatile rough machining process that can have high material removal rate and significant tooling cost savings.
Minimum Quantity Cryogenic Machining the 400 Degree Difference
D. Watts, MAG, Sterliing Heights, MO
Minimum Quantity Cryogenic Machining The 400 Degree Difference
The idea of sustainability is becoming more defined and better understood. However, most manufacturers still are not taking the necessary steps to implement newer proven technologies that employ the philosophy of sustainability. Generally speaking, manufacturers still associate sustainability with higher costs. However, when we break down the investment and operating expenses of “wet” manufacturing systems we begin to understand just how much they are costing us. One huge step towards sustainability is eliminating the costly consumable known as “coolant“. Minimum Quantity Lubrication (MQL) technology eliminates the large quantity of water and oil based coolants and replaces them with a small quantity of lubricant mixed with air. The air oil stream is precisely metered and delivered to the cutting edge. The philosophy of MQL technology is based on the principle that more isn’t better. Only use the quantity needed for the application, because enough is as good as a feast.
Manufacturers applying MQL are reaping the many sustainable benefits. Their workers are safer. Operators, skilled trades, and engineers are no longer exposed to the toxicity, bacteria, and fungi risks that come with traditional “wet” manufacturing systems. The metal chips produced in MQL applications are nearly dry and much cleaner. The chips are easier to recycle and more valuable as a recycled material.
Materials that are poor thermal conductors generally require cooling power that MQL cannot provide. As such, MAG’s vision for next generation dry machining is to evolve from their significant MQL expertise and replace or supplement MQL with Minimum Quantity Cryogenic (MQC) technology enabling higher cutting speeds and productivity.
Machinability of the Nickel Alloys Inconel 625 and 718
S. Turner1, C. M. Taylor1, A. Etxeberria2, P. Arrazola2, (1)The University of Sheffield, Rotherham, United Kingdom, (2)Advanced Manufacturing Research Centre, Catcliffe, Rotheram, United Kingdom
Machinability of the Nickel Alloys Inconel 625 and 718
Inconel 625 and Inconel 718 are nickel-based alloys which are heat and corrosion resistant, as such they are used in aerospace, petrochemical, nuclear and biomedical applications. Numerous previous studies have been conducted regarding the machinability of Inconel 718, but very little machinability data is available for Inconel 625. The aim of the study presented was to investigate the machinability of Inconel 625 and the more commonly-used Inconel 718, when cut with coated carbide tools. Inconel 625 was tested in its annealed form, whilst Inconel 718 was tested in a solution treated and aged condition. Tests were carried out for a turning process. The main focus of the study was on tool life and cutting forces, however some interesting insights are provided regarding chip formation and machining dynamics (vibration) issues.
Orthogonal cutting force measurements showed that for Inconel 718 there was a linear relationship between the feed rate (chip thickness) and cutting forces, whereas Inconel 625 showed a non-linear relationship in the feed range studied. This non-linearity was reflected by dynamic behavior documented when roughing Inconel 625 using RCMT round inserts, with vibration being observed only at certain feed rates.
VNMG rhombic, CNMG rhombic and RCMT round carbide inserts were tested for their performance in cutting Inconel 718. 15 minutes of tool life could not be achieved when machining Inconel 718 with VNMG inserts. Burring, depth of cut notch wear and tool edge fracture were key factors. CNMG inserts were more successful. The material removal rate achieved, and the total material removed per RCMT round insert, was 4 to 5 times the value achieved using the CNMG rhombic inserts, which shows the promise of round “button” inserts for roughing operations.
Machine Tool Genome Project
J. C. Ziegert, University of North Carolina at Charlotte, Charlotte, NC
For many machining operations, the onset of unstable chatter vibrations can limit the achievable material removal rate. Past research by Tlusty and others has shown how to create stability lobe diagrams that provide regions of stable and unstable cutting, and allow selection of non-intuitive machining parameters that can greatly improve productivity. However, creation of the stability lobe diagrams requires knowledge of the structural dynamic response of the tool-holder-spindle-machine system, typically obtained by experimental measurement. Given the huge number of combinations of machines, spindles, holders, and tools, the effort required to collect all of the required data experimentally is overwhelming; calling for an approach that can predict the tool point frequency response function for arbitrary tool-holder-spindle-machine combinations using minimum input information. This talk will describe an method for characterizing the "dynamic fingerprint" or "DNA" of each machine, spindle, and holder; and ways to analytically predict the tool point frequency response for arbitrary tools.
High Performance Machining of Titanium - The Holistic Solution
B. P. Erdel, Consultant, Pittstown, NJ
The attributes of Light-Small-Simple-Fast and Smart are permeating through-out industrial manufacturing in both Processes and Products. Advanced materials are at the core of it and manufacturing networks are following the materials from which innovative and advanced parts are made. Titanium is one of the most sought-after materials in the Aerospace Industry due to its superior strength and light weight. While titanium's superior strength-to-weight ratio makes it the designer's material of choice, machining it with productivity and cost-effectiveness continues to pose great challenges on the manufacturing floors throughout the Aerospace Supply Chain. However, High Performance Machining of Titanium can be achieved with robustness and relative ease by embracing the entire machining envelope and optimizing all parameters through a well-defined holistic approach. Machine Tool dynamics, Cutting Tool geometries, Precision Tool-Holding, accurate Workpiece-Clamping, advanced Cutting Fluids and well-tuned Machining Data have to be tuned to one another to machine titanium with predictability, high repeatability accuracy and economically. With a steady increase of composite material for structural parts, titanium usage is on a similar upswing for stacked material compositions. Here the titanium part of the stack determines the outcome of the advanced, holistic machining process as well.
Challenges and Opportunities for Future Aerospace Propulsion Systems
R. J. Harshman, ATI, Pittsburgh, PA
The ability to successfully to design and manufacture the airframes and engines for coming generations of commercial aircraft requires the availability of advanced materials systems capable of operating at performance levels beyond those currently available. To meet these requirements, today’s materials manufacturers face dual demands. First, they must develop profound customer understanding. Then they must combine this understanding with the technical capacity to develop and manufacture the advanced materials capable of satisfying current as well as next-generation design, performance and sustainability demands of airframe and engine OEMs.
ATI is addressing these needs on multiple fronts: first, by creating market sector teams charged with understanding the most pressing needs of the aerospace industry; second, by expanding its materials and manufacturing capabilities; and third, by integrating its fundamental materials understanding from microstructure and melting through semi-fabrication to net-shape processing.
Mr. Harshman will review the company’s efforts to enhance its customer understanding, advance its manufacturing capabilities and expand and integrate its scientific and engineering knowledge. He will also discuss the value he believes will be derived from ATI’s quantitative process understanding and the new horizons this understanding will create in the performance of titanium and nickel-based alloys.
Aluminum-Based Solutions for Tomorrow’s Airframe Structures
T. Warner, Constellium LLC, Voreppe, France
Tomorrow’s airframe structures will have to meet an ever-widening set of expectations: low weight and low cost remain key drivers, but increased maintenance intervals are now the industry norm. In addition technology robustness, reduced lead time and ecologically responsible manufacturing are increasingly required. Aluminum-based solutions have significant potential with regard to these expectations, both through the traditional route of improved alloy performance and via improved design and manufacturing approaches.
The major aluminum suppliers have a strong track record in focused new alloy development. Recent development emphases have included Al-Cu-Li alloys, giving rise for example to Constellium’s AIRWARE™ technology. These alloys combine the intrinsically improved density and stiffness due to Li addition with a significant step in strength-damage tolerance balance. The intrinsically good corrosion resistance of Al-Cu-Li alloys brings further potential, either with regard to reducing the cost of corrosion protection systems or by facilitating increased inspection intervals. The economic and environmental viability of such solutions also depends on the industry’s ability to recycle the scrap material efficiently; major progress in this field has been made over the last several years.
However, alloy developments only represent about half the potential improvements currently accessible with metallic structures, the remainder being associated with more efficient design and manufacturing approaches. For example, the cost of riveted skin-stringer panels can be improved by application of welding or bonding, thereby eliminating much of the complexity and cost of assembly. Moreover, moving from riveting to welding or bonding reduces the number of fatigue initiation sites associated with local stress risers and can thus bring significant weight benefits.
Over and above the technologies mentioned above, metallic solutions that explore higher potential but lower maturity technologies are being investigated. Examples include incorporating structural health monitoring capable features in wrought aluminum products, tailored property parts, and aeroelastic tailoring. All these have been demonstrated at relatively small scale in aluminum structures, and now need to be brought to a higher technology readiness level.
Illustrations of the aforementioned technologies will be presented, along with both calculated benefits in terms of airframe weight and estimates of their technology readiness dates.
Aluminum-Based Technically-Ready Aerostructural Solutions with a Quantum Leap In Performance
J. Liu, Alcoa Technical Center, Alcoa Center, PA
Alcoa has been at the forefront of every major milestone in aerospace history. Recent progress in the launching of composite-intensive aircraft has pushed us to take our innovation efforts to the next level. Intense efforts in the development of advanced alloy products with a quantum leap in performance have now resulted in a system of aluminum-based product solutions which are at a high level of technology readiness for applications. Application-specific product options for key structural components will be discussed and compared with incumbents. New advancements in Al-Li products for tension- and compression-dominated wing applications will be highlighted and compared with conventional alloy products. New high performance Al-Li fuselage alloy products will be discussed in light of their raised design drivers. New generation 7XXX and Al-Li “thick” products for internal structures of both metallic- and composite-intensive aircraft will be introduced. Advancements in Al-Li forging development will be presented.
Challenges and Opportunities for Future Aerospace Propulsion Systems
P. Adams, Pratt & Whitney, East Harvard, CT
In the field of aerospace propulsion systems, economic demand and concern for the environment has stimulated advancements in aircraft system design. Aircraft performance improvements depend largely on the engines. Historically, engine fuel burn has improved at rate of about 1% per year. With the cost of petroleum based fuels rising and no end in sight, the engine manufacturers must innovate to realize step change improvements to fuel burn, noise, and emissions.
Materials have played an important role toward improving propulsion system performance by enabling operation at higher temperatures and pressures. However, targeting improvements through material changes alone limits potential and may not fully address environmental demands. Changes in system architecture, combined with continued advancement of materials, has opened up the possibility to game changing improvements. Pratt & Whitney’s Geared Turbofan™ architecture has resulted in a double-digit percentage improvement in fuel consumption.
To fully leverage advantages of new engine system architectures, advancements in material systems and integrated materials solutions, such as hybrid-material construction and rapid manufacturing methods, must continue. The challenge now becomes the speed to develop and integrate new material technologies into the product as well as cost effectiveness of the technology. An overview of the recent advances in propulsion system design will be presented along with a review of how materials and manufacturing methods are playing a critical role in the development, realization and deployment of new systems with unprecedented performance and durability.
Affordability – Manufacturing’s Role in Aviation’s Growth
G. Warwick, Aviation Week & Space Technology, Washington, DC
The aircraft that will dominate aerospace manufacturing for the next decade and beyond are already entering service, in development or leaving the drawing board. The Boeing 787, Airbus A350 and Lockheed Martin F-35 have brought a significant shift to composites, but in the absence of new clean-sheet designs the opportunity for further major changes in materials and structures is now limited. However, there is growing potential for advances in manufacturing technology to help manufacturers push up production rates and drive down costs. Strong orderbooks on the commercial side and budget pressures on the military side will encourage investment in technologies that make aircraft more affordable and manufacturing more profitable.
New Developments in Titanium Fastener Technology
L. Haylock, Alcoa Fastening Systems, Torrance, CA
Titanium fasteners are widely used throughout the aerospace industry today, yet as the aerospace industry evolves the importance of these highly stressed components are often underestimated.. The high specific strength of titanium alloys have made it a very attractive material for aerospace fasteners but the increased use of Carbon fiber reinforced composite (CFRP) and hybrid structures have increased the importance of titanium as a fastener material. While the galvanic compatibility between titanium and CFRP is acceptable, the hybrid nature of large aircraft structure creates new structural challenges. The intrinsic high electrical conductivity of titanium fasteners relative to CFRP and the large number of fasteners used in aircraft construction combine to create a condition of a high probability of lightning attachment to fasteners when they are used for joining composite structures. Fasteners are normally used to join some of the most highly stressed structural members and are ideally located to be used a platform for structural health monitoring technologies. This presentation will cover recent developments in the titanium fastener technology and technology trends in the framework the evolving structural architecture of commercial aircraft.
Effects of Working and Heat Treatment on Microstructural and Mechanical Properties Evolutions in Ti-6Al-4V Fasteners
L. Zeng, L. Haylock, Alcoa Fastening Systems, Carson, CA
Titanium fasteners (Ti-6Al-4V) were traditionally used in aircrafts to achieve weight reduction and corrosion resistance. Recently, as the advancement toward composite airplane, the usage of titanium fasteners are increasing, partially due to its excellent compatibility with composite materials, and the microstructure and mechanical properties requirements tend to be more stringent. Thus, knowledge of the relationships between manufacturing processing variables and quality of Ti-6Al-4V fasteners, the microstructure and texture evolution from heading through thread rolling, and the mechanical properties, is crucial for the improvement of the manufacturing process to insure required properties. This evaluation program focuses on the microstructure and mechanical evaluation of Ti-6Al-4V fasteners. The selected fasteners from different stages of manufacturing processing, heading, heat treatment, grinding, and thread rolling, were evaluated by mechanical, microscopy, and X-ray techniques. The primary goal of the microstructure evaluation is to establish control over process variables that affect the quality and integrity of Ti-6Al-4V fasteners using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The mechanical properties characterization mainly includes shear testing and compression test at different orientations from as-received wire to fasteners at different strain rates. All these study can give us more comprehensive understanding of Ti-6Al-4V related to the production such as high strain rate deformation mechanism, phase behavior, and microstructural development, setting up a theoretical and experimental basis for extending the use of Ti-6Al-4V into new and innovative applications.
Novel Titanium Alloys for High-Strength Fastener Applications
C. Bugle1, A. Fadick1, T. Morton2, E. Crist3, (1)Dynamet Incorporated, South Park, PA, (2)The Boeing Company, Seattle, WA, (3)RTI International Metals, NIles, OH
This endeavor was undertaken to mature the development of novel titanium alloys Ti-185, Ti-5553 and modified Ti-6-2-2-2-2 for high-strength fastener applications. These alloys have shown promise as alternatives to the industry’s principal grades Ti-6Al-4V and Beta-C. Ti-185 (1Al-8V-5Fe) and Ti-5553 (5Al-5V-5Mo-3Cr) are meta-stable beta alloys that can be substantially strengthened by solution treatment and aging. This strengthening is achieved by the decomposition of retained beta into alpha + beta along with the decorous distribution of primary alpha phase. Ti-6-22-22 (6Al-2Sn-2Zr-2Mo-2Cr) is an alpha-beta alloy that also is strengthened through heat-treatment. Chemistry and melt methods have been refined to address past segregation issues and thermo-mechanical processing was tailored to optimize mechanical properties. Data generated from laboratory heat treatments on production hot-rolled bars will be presented. Evaluation of roll-formed threads will also be discussed.
Development of ATI 425® Alloy Fastener Stock
J. Foltz1, M. L. Young2, D. J. Bryan3, G. E. Vignoul2, (1)ATI Wah Chang, Salem, OR, (2)ATI Wah Chang, Albany, OR, (3)ATI Allvac, Monroe, NC
The assembly of modern aircraft relies heavily on fasteners. These fasteners are often composed of titanium alloys due to their corrosion-resistance, light weight, and mechanical performance. A new option to existing titanium fastener alloys is ATI 425® Alloy. This new fastener alloy meets and exceeds standard aerospace qualification criteria for titanium bars and wire in a solution-treated and aged condition. ATI 425® Alloy wires and bars can be produced in various sizes for aerospace fastener applications. Hot rolled ATI 425® Alloy wires generally have an average ultimate tensile strength above 195 ksi and an average double shear value above 115 ksi for sizes up to 0.531" diameter in a solution treated and aged condition. Mechanical testing, including tensile and double shear testing, and metallographic results from four final fastener stock sizes (0.188", 0.250", 0.406", and 0.531") in the as-drawn, mill annealed, and solution treated and aged conditions, will be discussed in this presentation. The performance and manufacturability of ATI 425® Alloy as fastener stock will also be highlighted.
High Strength Titanium Alloy VST3553 for Aerospace Fastener Application
M. Leder1, I. Y. Puzakov2, (1)VSMPO, Sverdlovsk Region, Russia, (2)VSMPO, Sverdlovsk Region, RI, Russia
The new near-beta titanium alloy VST3553 (Ti-3Al-5V-5Mo-3Cr) has a high degree of processibility which allows to manufacture aerospace fasteners both in hot and cold condition. At that, the deformation rate in cold condition can reach up to 75%. The following level of properties can be achieved after thermomechanical processing of VST3553 alloy: ultimate tensile strength in the range from 970 to 1715 MPa at relative elongation rate from 18 to 4% depending on the heat treatment regime. The manufacturing process for round bars in VST3553 alloy is developed; research carried out on metal structure and mechanical properties after heat treatment.
The Influence of Chemistry and Heat Treatment on the Mechanical Properties of Ti-3Al-2.5V Alloy
J. Ferrero, S. Sweet, Perryman company, Houston, PA
Over the past several years, the usage of Ti-3Al-2.5V for fastener applications has grown significantly. As the amount of composite used in airframes has increased, the number of titanium fasteners has also significantly increased. This change has also lead to an increase in the number of collars and sleeves used in the fastening systems. TheTi-3Al-2.5V alloy has been selected for these types of applications due to its ability to be cold formed and maintain moderate strength levels. Sleeves and collars had historically been produced from commercially pure titanium or stainless alloys. This study will evaluate the influence of chemistry, processing, and heat treatment on the properties and microstructure of this alloy.
Fatigue and Tightening Performance of Plasma Surface Hardening Treated Titanium Fastener for Composite Aircraft Structure
N. Tsuji, S. I. Tanaka, Tanaka Limited, Osaka, Japan
Recently, a number of structures in aircraft have been dramatically replaced by carbon fiber reinforced plastics (CFRP) composite materials. Titanium fastener is one of the most appropriate selections for fastening and joining CFRP materials because of galvanic and thermal expansion compatibility with composites. For nearly 50 years, titanium threaded fasteners has been used in solution treated and subsequent aging condition with minimum tensile strength of 1100 MPa (160 KSI). On the other hand, various surface treatments such as insulating coating have been often applied on titanium fasteners to prevent galvanic corrosion on aluminum materials and to obtain an adequate clamping force because titanium fasteners tend to gall due to its high friction characteristic and low hardness.
A newly developed conductive surface modification technique using plasma-carburizing was applied on externally threaded titanium fasteners for joining of CFRP composite structures and its mechanical properties including fatigue performance were evaluated. The fatigue strength of the modified fastener was higher than that of the unmodified fastener. The tightening performance of the modified fastener was significantly improved by the hardness increase on the thread surface. The modified fastener not only satisfied requirements of aerospace industry enough but also had a more efficient performance.
Provision of Critical Experimental Results for Emerging Titanium Powder Metallurgy Approaches - From Reduce Cost Powder to Forgings
P. Collins1, K. Akhtar2, P. Samimi1, H. Mohseni1, (1)Univeristy of North Texas, Denton, TX, (2)International Titanium Powder, Lockport, IL
The numerous research efforts associated with the wide variety of titanium powder metallurgy approaches provides many new challenges and opportunities. This talk will focus on experimental evidence to characterize structure at a wide range of length scales for some of the new powder approaches (e.g., the Armstrong Process), including complex morphologies, evidence for the location of trace levels of sodium, and the role of native surface oxide layers on consolidated interstitial levels. This talk will also provide preliminary microstructural details associated with additively deposited material that has been subsequently forged using deposition approaches that require less energy than melt-based additive manufacturing approaches.
Rolled Product Form Development and Optimization Using Blended-Elemental Powder-Based Billets of Ti-6AL-4V Alloy
S. El-Soudani1, J. Fanning2, M. Harper2, S. P. Fox2, V. S. Moxson3, V. Duz3, (1)The Boeing Company, Huntington Beach, CA, (2)TIMET, Henderson, NV, (3)Advanced Materials, Inc., Hudson, OH
The feasibility of rolling process development has been successfully demonstrated at Timet, Inc. in ambient environment using initial rolling preforms of blended-elemental hydrided titanium powder billets fabricated by ADMA using their titanium hydride-powder blended with master alloy aiming at Ti-6AL-4V composition, then direct-consolidated by cold isostatic pressing (CIP), and vacuum sintering. All elements in the pre-rolling billet preforms including aluminum, vanadium, oxygen, hydrogen, carbon, and nitrogen were within the AMS Specification limits. Measurements of tensile properties of the plate and sheet rolled billets using processing pathways initially either in the beta or in the alpha-beta ranges of preheat temperatures, showed equivalent or superior tensile properties as compared to rolling processed wrought ingot-based Ti-6AL-4V billet materials. While the rolling processing development for Boeing at Timet is currently aimed at meeting the generic rolling product Specifications, such as AMS 4904D, and/or ASTM B267-07, the successful rolling processing development at Timet was preceded by ADMA optimization of their fabricated pre-rolling billets, focusing on the CIP-and-sintering steps for reducing both oxygen and residual hydrogen contents to levels at or below the AMS Specification limits for Ti-6Al-4V composition (namely, oxygen content of 2000 ppm maximum, and hydrogen content of 125 ppm maximum). The goal of the optimization steps both at ADMA and Timet is to provide the best property balance of the blended-elemental powder-based rolled products spanning both plate and sheet ranges of thicknesses, while minimizing the required number of rolling passes from initial consolidated billet thicknesses as near as possible to the final product thickness, which provides just enough thermomechanical working of the powder-based billet to meet the Boeing-approved aerospace product specifications in terms of chemistry, microstructure and properties. The Boeing-executed test matrix included processing-microstructure-property correlations of tensile properties, S-N fatigue life, fatigue crack growth da/dN, fracture toughness per ASTM-E399-KIC (KQ), and stress-corrosion resistance as measured by the NACE-KISCC test TM0177 and/or the bolt-loaded ASTM G 168 standards. This paper examines correlations between powder-based, and ingot-based rolled products in terms of meeting AMS Specification requirements.
Development and Optimization of Rolled Product Forms Using Blended-Elemental Powder-Based Ti-6AL-4V Alloy
S. El-Soudani1, K. O. (. Yu2, E. M. Crist2, F. Sun2, V. S. Moxson3, V. Duz3, (1)The Boeing Company, Huntington Beach, CA, (2)RTI International Metals, Inc, Niles, OH, (3)Advanced Materials, Inc., Hudson, OH
The feasibility of rolling process development has been successfully demonstrated at RTI International Metals, Inc. in ambient environment using initial rolling preforms of blended-elemental hydrided titanium powder billets fabricated by ADMA using their titanium hydride-powder blended with master alloy aiming at Ti-6AL-4V composition, followed by direct-consolidation by cold isostatic pressing (CIP), and vacuum sintering. All elements in the pre-rolling billet preforms including aluminum, vanadium, oxygen, hydrogen, carbon, and nitrogen were within the AMS Specification limits. Measurements of tensile properties of the plate and sheet rolled billets using processing pathways initially in the beta then in the alpha-beta ranges of temperature, showed equivalent or superior tensile properties as compared to rolling processed wrought ingot-based Ti-6AL-4V billet materials. While the rolling processing development for Boeing at RTI is currently aimed at meeting the generic rolling product Specifications, such as AMS 4904D, and/or ASTM B267-07, the successful rolling processing development at RTI was enabled by rolling process modeling and a workability study at RTI, in addition to a preceding ADMA optimization of their fabricated pre-rolling billets, focusing on the CIP-and-sintering steps for reducing both oxygen and residual hydrogen contents to levels at or below the AMS Specification limits for Ti-6Al-4V composition. The goal of the optimization steps both at ADMA and RTI is to provide the best property balance of the blended-elemental powder-based rolled products spanning both plate and sheet ranges of thicknesses, while minimizing the required number of rolling passes from initial consolidated billet thicknesses as near as possible to the final product thickness which provides just enough thermomechanical working of the powder-based billet to meet the Boeing-approved aerospace product specifications in terms of chemistry, microstructure and properties. The Boeing-executed test matrix included processing-microstructure-property correlations of tensile properties, S-N fatigue life, fatigue crack growth rate da/dN, fracture toughness per ASTM-E399-KIC (KQ), and stress-corrosion resistance as measured by the NACE-KISCC test TM0177, and/or the bolt-loaded ASTM G-168 standards. This paper examines correlations between powder-based, and ingot-based rolled products in terms of meeting AMS Specification requirements.
Development of Low Cost Seamless CP-Ti Tubes
C. Lavender1, V. V. Joshi1, E. V. Stephens1, B. Johnson2, V. S. Moxson3, V. Duz3, (1)Pacific Northwest National Laboratory, Richland, WA, (2)Sandvik Special Metals Corp., Kennewick, WA, USA., Kennewick, WA, (3)Advanced Materials, Inc., Hudson, OH
Commercially pure titanium (CP-Ti) is primarily used in marine and chemical applications that rely on aggressive heat exchange conditions such as those employed in the desalinization and chemical, pulp/ paper and petrochemical production and in the aerospace industry as a conduit / ductwork material. The development of low cost CP-Ti-tubes will further enable their use in these and other similar processing industries thus increasing their process efficiency at a relatively lower cost. In order to overcome the cost barrier in developing the same the authors have developed a process to manufacture seamless CP-Ti tubes via a novel direct powder to product process using low cost titanium hydride feedstock powder. The present work details the development of dehydrided CP-Ti billets by CIP/Sinter and CIP/Sinter/HIP processes which were further subjected to hot-extrusion and pilgering to develop seamless CP-Ti tubes. The mechanical properties and behavior of these tubes were compared with those produced by standard ingot method by performing statistical analysis via instrumented burst tests.
Forming Limit Curves for Ti6Al4V Via Pneumatic Stretching
F. Abu-Farha1, L. G. Hector2, (1)Penn State Erie, Erie, PA, (2)General Motors R&D Center, Warren, MI
Forming limit curves (FLCs) and diagrams (FLDs) are essential tools for any sheet metal forming operation, especially in the automotive and aerospace industries. In addition to accurately describing the limits of material formability under various biaxial loading ratios, they are important for the finite element (FE) simulations of sheet-component forming operations. While the construction of FLCs is well-established for steels at ambient temperatures, their construction is challenging for lightweight alloys since the latter are typically formed at warm/high temperatures. The challenge is particularly great for titanium alloys, since forming temperatures are extremely high, exceeding the typical temperature limits for commercial mechanical stretching test setups. In this work, we shed some light on the feasibility of constructing hot formability curves for the Ti6Al4V alloy using the recently-developed “pneumatic stretching test”. The test best resembles the conditions encountered in actual superplastic forming (SPF) operations, and can be applied at very high temperatures without any frictional effects. Sheet samples are deformed at selected conditions (temperature and strain rate) by free pneumatic bulging into a set of progressive elliptical die inserts. The material in each of the formed domes is thus forced to undergo biaxial stretching at a distinct strain ratio, which is simply controlled by the geometry (aspect ratio) of the selected die insert. Material deformation is quantified using circle grid analysis (CGA), and the recorded planar strains are used to construct accurate friction-independent forming limit curves for the material.
Comparative Study on the Properties of Ti-6Al-4V Coatings Deposited by High Velocity Thermal Spray Methods
C. Lyphout1, N. Markocsan1, L. Östergren2, T. Klassen3, K. Binder3, (1)University West, Trollhättan, Sweden, (2)Volvo Aero Corporation, Trollhättan, Sweden, (3)Helmuth-Schmidt-University, Hamburg, Germany
Thermal Spray Technology is emerging as an interesting alternative method to welding, metal deposition and laser cladding. Besides conventional spraying processes like Plasma Spray, Powder Flame Spray, Wire Flame Spray, and High-Velocity-Oxy-Fuel spray (HVOF), recent development of High-Velocity-Air-Fuel (HVAF) and Cold Gas Dynamic Spray (CGDS) processes have demonstrated excellent aptitudes to deposit coatings of oxidation sensitive materials, such as Titanium alloys, due to processing at lower particle temperature combined with high particle velocity . In the present study, HVAF and CGDS processes have been used to apply Ti-6Al-4V coatings onto substrates of similar material. The objective was to establish the state-of-the-art feasibility of handing out CGDS and HVAF processes for repair applications of Ti-based alloys in the aerospace industry. Coating properties were evaluated through microstructure analysis, Vickers and Rockwell hardness testing, tensile adhesion strength and Young’s modulus evaluation by four-point bending test. Whereas HVAF sprayed coatings still exhibited a large inhomogeneous microstructure with high amount of oxides, CGDS process provided an oxides-free state with a low porosity level, conferring to the Ti-6Al-4V coating high adhesion strength to the substrate and relatively good mechanical properties.
Recent Inventions and Innovations in Induction Heating of Non-Ferrous Alloys
V. Rudnev, Inductoheat Inc., Madison Heights, MI
Presentation focuses on inventions and innovations recently developed in the area of induction heating of non-ferrous alloys. Variety of unique (patented or patent pending) technologies developed in the last 3-5 years will be discussed here, including but not limited to induction heating of solid and hollow billets, bars, various shaped components made of different alloys including titanium, aluminum, magnesium, super alloys, etc. Presentation also discusses different subtleties for using induction for heating various specialty alloys and irregular shape workpieces ensuring the temperature uniformity of the heated materials.
The Effects of Oxygen in Beta Titanium Alloys
D. J. Bryan, ATI Allvac, Monroe, NC
The effects of increasing oxygen content on alpha, alpha-beta, and commercially pure titanium alloys are generally well understood and reported in literature. As oxygen levels are increased above a critical level, alpha-2 formation and slip planarization result in decreased ductility, formability, and resistance to crack propagation. As a result of this understanding, oxygen maximums around 0.2 wt% or less have been established for most common titanium alloys.
The mechanisms and effects of oxygen in beta titanium are much less understood. Beta titanium alloys are dominated by the BCC phase and thus not necessarily subject to the same alpha-2 formation and subsequent slip planarization observed in alpha, alpha-beta, and commercially pure titanium alloys. The chemistry specifications for most beta titanium alloys, however, set the oxygen maximums at levels similar to alpha, alpha-beta and CP titanium alloys. This work explores the effects of oxygen on the mechanical properties and microstructure of two beta titanium alloys, ATI 5553™ Alloy (Ti-5Al-5V-5Mo-3Cr) and ATI 15Mo™ Alloy.
Properties of ATI 425® Alloy Tubing for Use in Aircraft Hydraulic Systems
M. E. Martinez, G. E. Vignoul, ATI Wah Chang, Albany, OR
New designs, and upgrades of legacy aircraft, are causing the aircraft OEM’s to incorporate 5,000+psi hydraulic systems into their latest models. The use of the traditional alloy Ti 3Al-2.5V in these designs necessitates a heavier gauge wall than is required for 3,000 psi systems and can result in increased airframe weight. Thus far, attempts to qualify higher strength tubing alloys such as Ti 6Al-4V Super ELI (SE) have been unsuccessful. ATI 425® Alloy (4Al-2.5V-1.5Fe-0.25O) is a cold workable titanium alloy demonstrating strength that is similar to Ti 6Al-4V and much higher than Ti 3Al-2.5V. The cold workability of ATI 425® Alloy allows the production of tubing without the concomitant reduction in oxygen required to make tubing out of Ti 6Al-4V. Initial research showed that ATI 425® Alloy exhibited improved fatigue properties over alloys such as Ti 6Al-4V SE and Ti 3Al-2.5V in sheet form. In tubing form, these enhanced properties may support the use of ATI 425® Alloy in a 5,000psi hydraulic system without an increased wall thickness and corresponding weight penalty. This presentation focuses on the tensile, bend, flare, flatten, fatigue and burst properties of ATI 425® Alloy tubing. Properties are compared to Ti 3Al-2.5V.
Fatigue and Fracture Behavior of Titanium Extrusions
B. Cherukuri, R. Porter, N. Minakawa, RTI International Metals Inc, Niles, OH
Extrusion is a near-net shaping process which reduces the buy-to-fly ratio, material consumption and also saves valuable spindle time during machining a finished part. Titanium alloy plate is processed by hot rolling, and while increasing the buy-to-fly ratio, it is preferred by many machining centers due to its versatility, since part dimensions can be readily changed, and due to the ability to nest multiple different parts in a single plate. Mechanical properties of Ti-6Al-4V extrusions in various conditions are presented and compared against standard and ELI grade-Ti-6Al-4V plate material. Second tier properties such as fracture toughness, fatigue and fatigue crack growth rate are compared, and show the excellent combinations of these properties that can be obtained in both product forms to meet customer specific application requirements. The dependence of these properties on microstructure will also be discussed.
The Qualification of ATI 425 ® Alloy Titanium for Boeing CH-47 Chinook Helicopter Rotor Blade Erosion Caps
K. W. Young1, M. E. Martinez2, (1)The Boeing Company, Ridley Park, PA, (2)ATI Wah Chang, Albany, OR
Erosion resistance is an important requirement in many aerospace applications, particularly for rotorcraft operating in desert environments. The leading edge of a helicopter rotor blade has a rotational tip speed of approximately 500mph and operates in harsh environments containing dust, sand and water particles. The Boeing CH-47 Chinook composite rotor blade leading edge structure is protected by metallic erosion caps, including a titanium nose cap over a relatively large coverage area, whose size, engineering and performance requirements dictate a controlled material and manufacturing process. ATI 425® Alloy titanium has been evaluated and qualified as an alternative material to the current Ti 6Al-4V CH-47 Chinook rotor blade erosion nose cap. An overview of this qualification program with a formed trial part is provided. Testing discussed includes static tensile, axial fatigue, erosion, bonding, hydrogen pickup, corrosion, and paint adhesion. The results of a destructively tested titanium cap test article are also discussed, and the performance and manufacturability of ATI 425® Alloy are highlighted.
On An Integrated Experimental and Computational Approach to Derive Phenomenological Equations to Predict Properties in Titanium Alloys
I. Ghamarian1, B. Welk2, D. Huber2, P. Collins3, H. L. Fraser2, (1)University of North Texas, Denton, TX, (2)The Ohio State University, Columbus, OH, (3)Univeristy of North Texas, Denton, TX
The development of tools to predict the mechanical properties based upon compositional and microstructural inputs in multi-component, multi-phase Ti-based alloys represents a significant challenge. One such solution is the development of high-fidelity databases and the subsequent application of non-linear modeling tools such as neural networks based upon a Bayesian framework to extract the underlying composition-microsructure-property relationships. This approach has resulted in successful tools for the prediction of properties but often is based upon complex equations that do not appear to be phenomenological. Thus, one must use new approaches in parallel with neural networks to derive the phenomenological equations. This talk will highlight the development of such rules-based models for the prediction of the tensile and fracture toughness properties of Ti6Al4V at room temperature. These models have been successfully used to isolate the influence of the individual microstructural features on the mechanical properties. This talk will then provide the framework, including integrated genetic algorithms and Monte Carlo approaches, to determine the first generation of the more robust phenomenological models.
Brazing of Titanium Honeycomb with Low-melting Zr-Ti-X-Y Brazing Alloy(s)
D. M. Lee1, G. E. Welsch1, Y. H. Kim2, (1)Case Western Reserve University, Cleveland, OH, (2)KITECH, Incheon, South Korea
Hypo-eutectic solidification is utilized to form low-melting filler alloys in brazing titanium and/or titanium alloys. Prior art (Zr54Ti23Ni15Cu8 ) eutectic filler alloy as well as new modified/improved filler alloys are used.
The eutectic alloys in the Ti-Zr-Ni/Cu system consist of the three phases, on ductile Zr-rich solid-solution phase and two brittle intermetalic Zr2Ni, and (Zr,Ti)2Ni phases. The Zr-rich hypo-eutectic alloys exhibit high strength, over 500MPa. They have the same low solidus temperature (as the eutectic) but a higher liquidus temperatures.
Using a hypo-eutectic Zr60Ti20Ni13Cu7 alloy T-joints of titanium were brazed at 950 °C. The fillets at the joints showed good wetting of the base materials and contained the Zr-rich and the other phases in fine and nearly homogeneous distribution. During holding at temperature the faying surfaces of Ti base metals inter-diffuse with the braze alloy, resulting in joint properties that were essentially equivalent to those of a diffusion-bonded layer. The joints thus ended up with excellent strength and toughness as might be expected from a diffusion-modified mostly-solid-solution-phase alloy.
The work demonstrated the use of low-melting filler alloys for brazing at relatively low temperatures. Well-wetted and quasi-homogenized fillet-alloys with good bond strength and toughness were formed. The alloys are suited for joining titanium structures such as honeycomb, fins, and pyramid-type structures.
Finite Element Simulation of Blow Forming of Scaled Combustion Chamber Expansion Zone
J. H. Yoon, J. T. Yoo, H. S. Lee, Korea Aerospace Research Institute, Daejeon, South Korea
The combustion chamber of space launch vehicle is one of key parts that affect the performance of space launch vehicle engine. The existing manufacturing route of the chamber employs machining, bulging, and brazing that induce material waste with cost increase. In order to reduce the drawbacks of existing manufacturing route, KARI has been searching an alternative manufacturing route, so that hot gas blow forming using diffusion bonded 4 sheets is studied. In the current study, finite element simulation of blow forming of combustion chamber expansion zone is described. The flow stress equation used in the simulation is determined by free bulging test. To avoid 3-D remeshing problem, shell element is selected with a proper treatment of bonded zone. From the simulation, blow forming pressure profile and thickness distribution are obtained. Moreover, the expected deformation mode shows that a reasonable configuration of cooling channel of the chamber can be formed. In the future, a study on diffusion bonding pattern should be carried out to enhance the final thickness distribution.
Ti-6Al-4V Production-Scale Sheet for Low Temperature SPF Applications
R. L. Porter, E. M. Crist, RTI International Metals, Inc, Niles, OH
Part manufacturers have sought to reduce the temperatures used for the superplastic forming (SPF) of Ti-6Al-4V sheet through reduction in the grain size. Some of the primary reasons include; poor life of the stainless / alloy steel dies, platens and heating elements at typical SPF forming temperatures of 1650-1700°F (899-927°C), and also formation of an alpha case layer on titanium during forming. Dies are expensive to manufacture, typically have long lead times and require significant cleaning and rework when used at higher temperatures / multiple thermal cycles. Furthermore, the alpha case layer formed on the titanium parts must be removed through conditioning and chemical milling processes that result in reduced yield and produce associated process wastes. Therefore, part manufacturers comfortable with the Ti-6Al-4V alloy have requested fine grain Ti-6Al-4V sheet in order to take advantage of low forming stress at temperatures less than 1500°F (816°C) in order to minimize these deleterious effects. Here, the mechanical properties, SPF characteristics (flow stress, m-value) as a function of strain rate and temperature, and microstructure of RTI Ti-6Al-4V production fine grain as compared to standard sheet will be discussed, along with results from RTI internal SPF trials.
Evaluation of near-Beta Titanium Forgeability, Heat Treat, and Testing Capabilities
L. Moody, Weber Metals, Paramount, CA
Near-beta alloys have much to offer aerospace applications, with many new alloys being developed to provide better forgeability, ductility, fracture toughness, and strength than traditional alloys. This presentation will provide an overview of near-beta alloys forgeability, heat treat response, and testing in closed die forging configurations.
Ti-5553 Wrought Processing and Heat Treatment Optimization
N. Sonnentag, ATI Ladish Forging, Cudahy, WI
The Ti-5Al-5V-5Mo-3Cr alloy offers a solution to thermomechanical processing challenges commonly associated with many commercially available beta and near-beta titanium alloys.
Wrought processes and heat treatment conditions producing high strength conditions are identified and discussed. Processes yielding an optimal balance of strength, ductility, and fracture toughness are selected for use on full-scale wrought Ti-5553 alloy components.
Wrought processing parameters and heat treatment will be reviewed and resulting mechanical properties and correlating microstructures will be presented.
Super Thin near Net Extruded Shapes
C. Delaunay, P. Munch, CEFIVAL, PERSAN, France
Super Thin Near Net Shapes allow dramatic increase in buy to fly ratio. Since 2007, CEFIVAL has developed several type of titanium alloys extrusion for mechanical engeneering application, Grade 2 (T40) , Grade 9 (TA3V2.5) and finally TA6V4. Benefits from these super thin near net shape extrusions can be obtained with an enhanced control of each manufacturing step : compact press extrusion, tool design , finishing , lubrication, heat treatment and dedicated machining techniques . Directionnal properties and typical applications are presented as well as potential developments with new engeneering alloys. Further increase is possible with cooperative processing between several technologies : shape forming , joining technics and additive manufacturing.
Linear Friction Welding of Ti Aerospace Structures
M. J. Russell, R. Freeman, TWI Ltd, Cambridge, United Kingdom
This presentation will provide an update on recent work at TWI on the development and industrialisation of Linear Friction Welding (LFW) for critical aerospace structures in Ti alloys.
LFW is currently used in industry for the manufacture of front stage compressor blisks, typically in Ti-6Al-4V. The process is also under development for intermediate stage blisks, in both Ti and Ni alloys. This presentation will demonstrate the application of the process to a 42 blade Ti-6Al-4V blisk and will summarise the key benefits of LFW technology for this case.
LFW is also under development for the manufacture of structural components, mainly in Ti alloys. LFW is used in this application to allow solid phase additive manufacture of simple block shapes to create part pre-forms. Such pre-forms typically offer significant production cost and time advantages when compared to solid block product and heavy section forgings. The advantages of LFW manufacture will be demonstrated by considering a recent test case component produced at TWI.
Finally, this talk will summarise the general process development and industrialisation strategy typically adopted at TWI for new LFW applications. The approach makes use of a range of LFW machines (from simple lab equipment through to industry standard state-of-the-art equipment) and employs a stage gate review process to manage the advancement of technology readiness level for each new application.
F-35 Direct Manufacturing: Material Qualification Results
S. D. Needler, Lockheed Martin Aeronautics Company, Fort Worth, TX
The F-35 Program is actively pursuing qualification of Direct Manufactured (DM) titanium alloy structural hardware. The F-35 DM process is an additive manufacturing procedure using an electron beam (EB) vacuum chamber, feedstock weld wire, and closed-loop process controls to ensure a consistent product. Lockheed Martin has generated material specifications to define the DM material characteristics and is currently engaged in the material qualification program that is scheduled for completion first quarter 2012.
The primary advantages of the F-35 EBDM process are affordability benefits derived from a reduction in raw materials and machining expenses as well as a significant reduction in lead times from a concept design to prototype hardware to production parts. The F-35 EBDM process for fabricating large structural hardware is proving its viability over other additive manufacturing techniques due to its large deposition rates (greater than 5 lbs/hr and increasing) and its customizable sized chambers (currently up to 20’ x 7’ x 5’ and several hundred pounds).
A necessity before embarking on a material qualification test program is to define a fabrication process that can and will produce a consistent product. This has been accomplished with the selection of a closed loop process control system jointly developed with Sciaky, Inc. The system has been optimized for the repeatable deposition of large titanium pre-forms using F-35 specifications.
The objective of this presentation will be to report the results of the materials qualification test program. This test program consists of ten (10) large pre-forms (approximately 250 lbs – 300 lbs of deposited titanium) that were sectioned to more than 1700 coupon test specimens. Testing includes static and fatigue evaluations and the results will be directly compared to existing F-35 Program design properties.
ATKINS – Additive Manufacturing for Reduced Lifecycle Energy Use
P. Edwards, Boeing Research & Technology, Seattle, WA
The aim of Atkins is to fundamentally migrate the design, manufacturing and distribution of goods and components away from the high energy-intensive methodologies that we use today to a more sustainable method of production, service and distribution to the consumer. This low-carbon design, manufacturing and service philosophy will be enabled by the unique characteristics of Rapid Manufacturing (RM). This project has been a collaboration of companies, led by the University of Loughborough in the United Kingdom, with support of the UK Government's Technology Strategy Board. Boeing's focus on the project has been to identify potential part candidates, support the design optimization for RM and perform the material, structural and business case analysis needed to implement this new technology. In this presentation, detailed information will be provided on the microstructural and mechanical performance of Ti-6Al-4V materials produced by RM, including static strength, fracture toughness, fatigue life and crack growth resistance. A case study will also be presented where a candidate part was selected, produced by RM and tested in fatigue to validate coupon data. It was found that while RM can be used to reduce manufacturing energy utilization and lifecycle energy consumption by reducing part weight, mechanical performance, particularly in fatigue, and overall manufacturing cost are still barriers for commercial aerospace implementation.
Fluoride Ion Cleaning As a Pre-Braze Process
R. Kornfeld, Hi-Tech Furnace Systems, Inc., Shelby Township, MI
Fluoride Ion Cleaning (FIC), synonymous with Hydrogen Fluoride (HF) cleaning is an extremely effective process for the removal of metallic oxides from metal alloys. It was developed by a major jet engine manufacturer as a cost effective repair process for nickel based airfoil components such as turbine blades and vanes. Today it is widely used to prepare nickel and cobalt based supper alloys for braze repair / Activated Diffusion Healing (ADH) on jet engines and industrial gas turbines.
Conventional processes such as Hydrogen Cleaning were effective for a wide range of stainless steels, cobalt and nickel based alloys. However hydrogen is not very effective on alloys containing significant amounts of aluminum and titanium. These two metals severely oxidize to form complex spinels on hardware surfaces that penetrate deeply into existing cracks. Only cleaning methods utilizing the fluoride-ion technique are currently capable of removing these deeply imbedded oxides. FIC utilizing HF gas offers a simpler, more precise and consistent alternative to other more complex techniques. These reactions are illustrated by the following:
1. 6HF + Al2O3 à 2AlF3 + 3H2O
2. 4HF + TiO2 à TiF4 + 2H2O
3. 6HG + Cr2O3 à 2CrF2 + F2 + 3H2O
In addition to removal of the oxides present on the surface and within cracks, surface depletion of elements such as titanium and aluminum also occurs which enhances brazeability by removing oxide reformers. These reactions are illustrated by the following:
1. 6HF + 2Al à 2AlF3 + 3H2
2. 8HF + 2Ti à 2TiF4 + 4H2
The depletion reaction is a function of the reaction temperature, the concentration of HF and alloy composition.
Advancements in Vacuum Aluminum Brazing
M. Orfe1, W. Powers2, (1)PV/T Inc., Rancocas, NJ, (2)AeroSPC Inc., Greer , SC
The PV/T division of Consarc Corporation, an Inductotherm Group Company, has responded to aerospace industry demands for better process controls, data archiving and cleaner technology. The desire for vacuum technology over salt bath as a “cleaner process” created needs for improved vacuum levels, temperature uniformity for NADCAP & AMS2750D pyrometry requirements, and the Quality Management System requirements of AS9100C related to configuration management, recipe control and process records. Utilizing improved distributive control systems, interactive touch screen human interface, recipe control, Microsoft Sequel Server database and Crystal Reports, the total package meets all of these requirements.
Additive Manufacturing of Titanium and AMC
I. D. Harris, EWI, Columbus, OH
Recent developments in welding and additive manufacturing of titanium and other aerospace alloys will be presented, with a focus on high power laser and hybrid laser arc welding. Welding processes covered, with application examples, will include high power laser and hybrid laser arc welding (HLAW). Additive manufacturing processes discussed will include laser and EB powder bed and blown powder processes, again with example applications. Developments in emerging processes such as hot wire GTAW will also be presented.
For additive manufacturing (AM) of metals, the very large cost to develop the required mechanical property database for a wide array of processes, materials, application end use, and market specific requirements warrants a cooperative and collaborative approach, especially where there is reasonably common interest to develop the mechanical properties needed to qualify a particular process for a particular market, whether this be full FAA flight qualification, or some other qualification.
While additive manufacturing technology development efforts are underway in many locations worldwide, the US aerospace community lacks basic data for the properties achievable with particular material grades and AM processes. In fact, the creation of an AM “properties database” was the most highly voted need identified in forming the Additive Manufacturing Consortium (AMC). Development of a shared database of additive manufacturing properties is thus a major element of the work of the AMC. MMPDS is seen as the model. Progress in this area will be presented.
Innovative Induction Welding of Thermoplastic Composites
C. M. Worrall, TWI Ltd, Cambridge, United Kingdom
The recent years have seen a renewed interest in thermoplastic composites for high-end applications, especially aerospace, where their high performance is required and higher material cost is affordable when amortised over high volumes. Compared to thermosets, thermoplastic composites (TPCs) offer shorter processing times to meet rising production rates. This makes TPCs an attractive option for the aerospace industry, but as yet there has not been a significant uptake of TPCs for structural applications. One reason behind this has been joining. In aircraft, composite parts are traditionally joined by mechanical fastening. Unlike thermosets, TPCs can be welded; a process that does not cause damage by cutting holes for the fasteners, and offers advantages in terms of weight and speed. Since the introduction of materials such as APC-2 (Carbon fibre reinforced PEEK) in the 1980s many studies have been carried out on fusion bonding of TPCs.
TWI was at this time also investigating joining possibilities of TPCs in several projects, but as a member based organisation, these projects were confidential and none of the results were published, until recently. TWI has continued to investigate fusion bonding of TPCs and has recently invented a new method for welding thermoplastic composites such as Carbon fibre reinforced PEEK. The technique does not employ a metallic implant but uses the conductivity of the carbon fibres themselves. This is nothing new, but by using a particular combination of parameters and properties, TWI’s method has the advantage that the heat generated by the induced eddy currents is concentrated around the joint interface, rather than close to the top surface of the composite where the proximity of the induction coil is greatest. This avoids the problem of having to remove excess heat from the surface of the composite to avoid thermal damage, and ensures that the power delivered by the coil is used to produce the joint and is not wasted. It can also be applied to very thick laminates as the increased power requirement to penetrate the laminate is concentrated at the interface and excess, unnecessary heat is not produced.
Fracture Properties of Friction Stir Welded Titanium Alloy, Ti-6Al-4V
A. M. Cantrell1, R. Mamidala2, P. D. Edwards3, D. G. Sanders3, B. D. Flinn2, (1)Jorgensen Forge, Seattle, WA, (2)University of Washington, Seattle, WA, (3)The Boeing Company, Seattle, WA
A product driven friction stir welding process has been refined to create butt-welds from two sheets of Titanium 6Al-4V (ultra fine grain). Weld specimen testing was completed on 3 different welded process conditions and the base material. This investigation includes macrostructure, microhardness, tensile properties, and fracture resistance evaluations of the weld specimens. The testing and examinations were conducted in accordance with industry standard testing specifications (e.g. ASTM E3, E407, E384, E8, E399, & E561). The weld microstructure in the stir zone is defined as refined and distorted grains of alpha in a matrix of transformed Beta containing acicular alpha. It was found that increase in alpha phase and grain refinement results in increased hardness, and increasing transformed beta in acicular alpha form which in turn results in an increase of toughness. The noted general trends in mechanical properties from “As Welded” (AW) to “Stress Relieved”(SR) conditions exhibited decrease in ultimate tensile strength and yield strength with a small increase in ductility and a large increase in fracture toughness.
Porosity Formation and Control When Laser Welding Titanium Alloys
J. Blackburn, C. Allen, A. Khan, P. Hilton, TWI Ltd, Cambridge, United Kingdom
The development of a laser welding process for titanium alloys which produce welds with acceptably low levels of weld metal porosity, with a high confidence interval, is a key step in encouraging the uptake of this technology for the fabrication of high-performance titanium alloy aerospace components. The advantages offered by this joining technology include high productivity, low heat input and easy robotic automation. This paper reviews recent research performed by TWI Ltd to understand and prevent porosity formation mechanisms when welding titanium alloys with 1µm wavelength laser sources. Three different strategies for porosity control were developed for welding titanium alloys with fibre delivered YAG lasers; a directed gas jet, a modulated laser power, and a dual focus arrangement. Characterisation of the three welding processes using high speed video and optical emission spectroscopy techniques, combined with a thorough assessment of the weld qualities produced, has allowed the effects these strategies have on the process dynamics and the formation of porosity to be determined. These techniques are compared with additional research performed using state-of-the-art Yb-fibre lasers, which are capable of being focussed into power densities exceeding 100kWmm-2 whilst maintaining an industrially acceptable stand-off distance and depth of focus. These techniques for keyhole laser welding of titanium alloys, combined with research being performed by other research institutes and aerospace companies, should encourage the uptake of keyhole laser welding for fabricating near-net-shape high-performance aerospace components.
Recent Developments in Stationary Shoulder Friction Stir Welding
M. J. Russell, R. Freeman, TWI Ltd, Cambridge, United Kingdom
This presentation will highlight recent development work at TWI in the area of Stationary Shoulder Friction Stir Welding (SSFSW). SSFSW is a variant of FSW where separate tool probe and shoulder components are used and only the tool probe component rotates. The result is a more linear heat input into the workpiece material and a keyhole type welding process. Process heat input is reduced, as are the key process forces (and hence machine requirements). Weld surface quality is typically much improved, and less thermal damage is caused to the workpiece (particularly in age-hardening Al alloys).
SSFSW has the potential to replace conventional FSW in a number of current applications, and allows FSW technology to be extended to new materials and new workpiece geometries. This talk will present the results of recent trials in a high strength 7xxx series Al alloy where the heat input and weld quality achievable by SSFSW has been directly compared with that of conventional FSW. The presentation will also highlight recent trials on welding of challenging joint geometries including 90 degree corner joints and T section parts, including the in-situ generation of corner fillet radii (and other features) by adding filler wire during welding.
SSFSW has been the subject of considerable development work at TWI over the last decade and is now starting to find industrial applications in a number of sectors, including aerospace.