Mohsen Seifi, Matt Dahar, Ron Aman, Ola Harryson, Jack Beuth and John Lewandowski have published a paper in a special issue on Additive Manufacturing in the March issue of Journal of Materials (JOM) entitled: Evaluation of Orientation Dependence of Fracture Toughness and Fatigue Crack Propagation Behavior of As-Deposited ARCAM EBM Ti-6Al-4V.
Abstract— This preliminary work documents the effects of test orientation with respect to build and beam raster directions on the fracture toughness and fatigue crack growth behavior of as-deposited EBM Ti-6Al-4V. Although ASTM standards exist for determining the orientation dependence of various mechanical properties in both cast and wrought materials, these standards are evolving for materials produced via Additive Manufacturing (AM) techniques. The present work was conducted as part of a larger America Makes funded project to begin to examine the effects of process variables on the microstructure and fracture and fatigue behavior of AM Ti-6Al-4V. In the fatigue crack growth tests, the fatigue threshold, Paris law slope, and overload toughness were determined at different load ratios, R, while fatigue precracked samples were tested to determine the fracture toughness. The as-deposited material exhibited a fine-scale basket-weave microstructure throughout the build and although fracture surface examination revealed the presence of unmelted powders, disbonded regions and isolated porosity, the resulting mechanical properties were in the range of those reported for cast and wrought Ti-6Al-4V. Remote access and control of testing was also developed at CWRU to improve efficiency of fatigue crack growth testing.
The published paper can be accessed:
M. Seifi, M. Dahar, R. Aman, O. Harrysson, J. Beuth, J.J. Lewandowski, JOM 67 (2015) 597.