Microstructure and mechanical properties of laser additive manufactured novel titanium alloy after heat treatment

A novel α+β titanium alloy with multi-alloying addition was designed based on the cluster formula 12[Al-Ti12](AlTi2)+5[Al-Ti14](AlV1.2Mo0.6Nb0.2) which was derived from Ti-6 Al-4 V. The nominal composition of this novel alloy was determined as Ti-6.83 Al-2.28 V-2.14 Mo-0.69 Nb-6.79 Zr. In this study, the novel alloy and Ti-6 Al-4 V alloy samples were prepared by laser additive manufacturing. The microstructure, micro-hardness, room/high temperature tensile properties of the as-deposited samples were investigated. Compared to Ti-6 Al-4 V, the novel alloy has much higher room and high temperature(600 ℃) tensile strengths, which are 1,427.5 MPa and 642.2 MPa, respectively; however, it has a much lower elongation(3.2%) at room temperature because of the finer microstructure. To improve the elongation of the novel alloy, heat treatment was used. After solution at 960 ℃ or 970 ℃ for 1 h followed by air cooling and aging at 550 ℃ for 4 h followed by air cooling, a unique bi-modal microstructure which contains crab-like primary α and residual β phase is obtained, improving the compression elongation by 80.9% compared to the as-deposited samples. The novel alloy can be used as a high-temperature and high-strength candidate for laser additive manufacturing.