Effects of altered hot isostatic pressing treatments on the microstructures and mechanical performance of electron beam melted Ti-6Al-4V

A wide range of post process hot isostatic pressing (HIP) studies of electron beam additively manufactured Ti-6Al-4V in this research program have shown that cooling rates of 103 °C/min from temperatures above and below the beta transus produced acicular alpha-prime martensite characteristic elongations < 10%. Optimum yield strength (0.9 GPa), UTS (1.0 GPa), and elongation (∼14%) were achieved for slow cooling (at 102 °C/min) from 850 °C HIP which produced a dense, Widmanstatten alpha structure within the retained, as-fabricated columnar grains by alpha-prime decomposition. These results suggest that manipulation of AM process parameters to produce a small-grain, equiaxed microstructure, HIPed below the beta transus and slow cooled, will have a wide range of superior, isotropic mechanical properties corresponding to a Widmanstatten alpha microstructure within the equiaxed grains.