Particle erosion induced phase transformation of different matrix microstructures of powder bed fusion Ti-6Al-4V alloy flakes

In this study, powder bed fusion Ti-6Al-4V alloy flake was subjected to heat treatment at 800^◦ C for 4 h for inducing the complete transformation of the α’ phase into the α+β phases. An erosion experiment with 450 µm mean particle diameter of Al₂ O₃ particles at a 90^◦ impact on both the as-powder bed fusion (PBF) Ti-6Al-4V and the 4-h 800^◦ C heat-treated specimens to clarify the particle erosion-induced phase transformation behavior and its effect on mechanical properties. Particle erosion-induced phase transformation to the α phase was observed on both the as-PBF Ti-6Al-4V and the heat-treated specimens. It brought about a sequential formation from the surface to the bottom: (1) a surface softened zone, (2) a hardened zone, and (3) a hardness stabilization zone. The as-PBF Ti-6Al-4V was positively eroded by erosion particles, decreasing strength and ductility. In the case of the heat-treated specimens, we found decreased strength yet an increased ductility.