Microstructure and mechanical properties of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy fabricated by arc additive manufacturing with post heat treatment

Wire arc additive manufacturing (WAAM) can achieve low-cost, short-cycle manufacturing of titanium alloys and has promising application prospects. In this paper, the microstructure and mechanical properties of both as-deposited and heat-treated Ti-6.5Al-3.5Mo-1.5Zr-0.3Si(TC11) alloys fabricated by WAAM were investigated. The results show that continuous grain boundary α(α_GB) phase and basket-weave microstructure can be observed in the as-deposited TC11 alloy. And the as-deposited alloy exhibits high ductility but low strength. After the annealing treatment, the microstructure becomes thicker and the strength becomes lower. Accordingly, a duplex heat treatment near β transus was designed. We can observed that the content of α phase in the microstructure was gradually decreased, and the continuous α_GB was broken gradually. As the temperature increases, the strength and ductility of TC11 alloy increase first and then decrease, and the best comprehensive mechanical properties are achieved at 970℃.