The role of microstructure and strain rate on the mechanical behavior of Ti-6Al-4V produced by powder metallurgy

Hydrogen sintering and phase transformation (HSPT), a powder metallurgy process, has been previously shown to produce desirable microstructures in Ti-6Al-4V components with corresponding excellent static and fatigue tensile properties. In the current study, three microstructures produced by HSPT and one produced by traditional wrought processing were tested under compression at strain rates of 0.001, 0.1, and > 1000 s(-1). The wrought condition exhibited the best toughness at 0.001 s(-1), but had the worst performance at both 0.1 and > 1000 s(-1) strain rates. The HSPT condition with a globularized microstructure performed the best at 1000 s(-1). From microstructural analyses, it is shown that the wrought condition had strong macroscopic texture consistent with hot rolling above the beta-transus temperature. It is proposed that this macrotexture made the wrought material susceptible to relatively early-onset shear banding at all but the lowest strain rate. Being a powder metallurgical process with no mechanical working, this macrotexture does not form during the HSPT process.