L. E. Murr, S. M. Gaytan, M. I. Lopez, E. Martinez, F. Medina, R. B. Wicker, University of Texas at El Paso, El Paso, TX
Additive layered manufacturing (ALM) has emerged over the past two decades as rapid prototyping, solid freeform fabrication and direct digital manufacturing mostly utilizing laser beams to fabricate complex, 3-dimensional (3D) components by successively stacking selectively melted powder layers one layer at a time. More recently, electron beam melting (EBM) systems have been developed for layer-based manufacturing.
In this study, Ti-6Al-4V powder (~30 mm mean diameter) was used to build a variety of fully dense prototypes as well as complex, structural-geometrical mesh prototypes and full density-to-graded density monolithic prototypes by EBM. The mesh arrays, in particular, can have stress-directed geometrical structures which, together with dimensional variations, can produce very strong, light-weight aeronautical or aerospace components and prototypes superior to metal foams. In addition, because of the electron beam rastering speeds and configurations, the microstructures and related mechanical properties of layered manufactured prototypes can be altered or graded. Optical metallography as well as scanning and transmission electron microscopy have been used to characterize variations in alpha (hcp) and alpha-prime (hcp) martensite phase microstructures, while both Vickers microindentation (HV) and Rockwell C-scale (HRC) hardnesses have been measured for these microstructures. Solid prototypes exhibit values of HRC 35 to 45 while fine mesh prototypes exhibit values of HV 480. In addition, build defects have been characterized in relation to the development of quality control and other certification issues for these unique prototypes using optical metallography and scanning electron microscopy.
Summary: This paper represents novel manufacturing concepts for aerospace applications of titanium alloys as well as the detailed characterization of product/prototype microstructure-propoerty relationships. In addition, this work seeks to develop quality control and certification for additive layered manufacturing by electron beam melting.
