A novel method to modify the microstructure and mechanical properties of direct energy deposited α + β titanium alloy

Abstract

This study employs multiple subcritical β/α transformation temperature annealing (MSA) heat treatments in order to eliminate the detrimental effects of continuous grain boundaries α phase (αGB) and the grain boundary Widmanstätten α phase (αWGB) on the mechanical properties of Ti-6.0Al-2.5Nb-2.2Zr-1.2Mo alloy fabricated through direct energy deposition (DED) technique. The width of the α lath increase with the increase in the number of heat treatments, while the aspect ratio decreases. The αGBs start to discontinue after once heat treatment and fully disappear after three times heat treatment. At this point, αWGB discontinued. After six times heat treatment, the strength and plasticity of Ti-6321 alloy were improved. This method effectively enhances the comprehensive mechanical properties of dual-phase titanium alloys.