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Wednesday, June 4, 2008 - 8:00 AM

Generation II Materials Science for Welds and Advanced Materials

D. L. Olson, J. E. Jackson, B. Mishra, M. J. Kaufman, Colorado School of Mines, Golden, CO; T. A. Siewert, A. N. Lasseigne-Jackson, National Institute of Standards and Technology, Boulder, CO; M. Pinkas, A. Landau, Nuclear Research Center, Beer Sheva, Israel

Advanced welded and processed materials increasingly use smaller dimensions, steeper gradients, and greater numbers of interfaces. Welds exhibit complex microstructures with gradients of composition, microstructure, and properties on the microscopic and macroscopic scale, which has a significant effect on cracking, nucleation, and other important material properties. When steep gradients or small dimensions are present, non-linear behavior of the chemical, electrical, and strain fields may occur. The consideration of higher-order mathematical terms in classical equations will enable deeper insight into this non-linear behavior. A new "Generation II" materials science needs to be explored to explain the non-linear behavior of welds and advanced materials.

 Weld metal also has composite-like features that may be engineered to achieve exceptional combinations of properties. Composite theory can be used to control numerous phenomena that occur during welding to create micro- and macro-structural variations that are engineered for better properties. Advanced non-destructive practices based on physical property measurements can allow for more comprehensive characterization of weld microstructure and properties. Electronic, magnetic, electromagnetic, and elastic NDE tools can be used separately or in combination to characterize the microstructure, phase stability, and aging during service.

 

When microstructural features are of dimensions of less than 100 nanometers, they exhibit non-linear chemical and electronic behaviors that should offer characteristic signatures about the structural details. Properties that can be assessed with wave analysis techniques, such as eddy currents and elastic waves, offer the ability to focus on certain microstructural details by the selection of frequency or amplitude of wave perturbations and reflected waves. The utilization of non-destructive property characterization by various wave analyses and NDE techniques will be described. New analytical practices need to be developed, established, and taught. Welding science and engineering is not mature, but must address revolutionary new concepts and applications beyond the traditional evolutionary paradigm.

 

 


Summary: Advanced welded and processed materials increasingly use smaller dimensions, steeper gradients, and greater numbers of interfaces. Welds exhibit complex microstructures with gradients of composition, microstructure, and properties on the microscopic and macroscopic scale. Heterogeneous areas such as dislocations, crack tips, secondary phases, and ceramic-metal interfaces are especially likely to exhibit non-linear chemical, electrical, and strain fields. These gradients have a significant effect on cracking, nucleation, and other important material properties. When steep gradients or small dimensions are present, non-linear behavior of the chemical, electrical, and strain fields may occur. The consideration of higher-order mathematical terms in classical equations such as the equations of fracture and nucleation will enable deeper insight into this non-linear behavior. A new "Generation II" materials science needs to be explored to explain the non-linear behavior of welds and advanced materials.