Analysis of microstructural facet fatigue failure in ultra-fine grained powder metallurgy Ti-6Al-4V produced through hydrogen sintering

The hydrogen sintering and phase transformation (HSPT) process is a powder metallurgy method that produces Ti-6Al-4V with fatigue properties rivaling wrought processed Ti-6Al-4V. Previous fatigue work on HSPT Ti-6Al-4V has shown failure to be frequently caused by microstructural facets, which were believed to be grain boundary (GB) alpha phase. This belief conflicts with other reports as fatigue failure typically occurs across alpha colonies or primary alpha grains, not GB alpha. In this work, electron backscattered diffraction is used to identify these facets as GB alpha. Furthermore, alpha simple geometric model predicting the effective slip length of GB alpha is presented.