Microstructural evolution and its effect on the mechanical behavior of Ti-5Al-5Mo-5V-3Cr alloy during aging

Development of different microstructures with a phase precipitates by a series of aging of Ti-5Al-5Mo-5V-3Cr (mass%, Ti-5553) alloy and their influences on the mechanical behavior were studied. Coarse acicular a phase formed in the solution treated (ST) samples, while ultrafine equiaxed a phase formed in the high-pressure torsion deformed (HPTed) samples. The strengthening by the precipitation of a phase could be explained by the Hall-Petch relationship between the yield strength and the alpha-to-alpha interphase spacing. The Hall-Petch coefficient of the HPTed samples was larger than that of the ST samples, because the equiaxed a phase was harder than the acicular a phase. The ductility of the HPTed samples was enhanced by the homogeneous distribution of equiaxed alpha phase.