Achieving fully-equiaxed fine β-grains in laser-additive-manufactured Sn-free high-temperature titanium alloy designed by cluster formula

Conventional high-temperature titanium alloys contain Sn as their essential alloying element. Upon additive manufacturing, these alloys exhibit insufficient mechanical properties due to the presence of coarse β-columnar grains. In this work, Sn-free high-temperature Ti-5.5Al-11.2Zr-4.8Ta-1.6W-0.5Si alloy with fully-equiaxed fine β grains was designed targeted for additive manufacturing on the basis of the composition formula of Ti65 alloy. This alloy shows good additive manufacturability and tensile strengths. Its composition formula satisfy α-{[Al–Ti₁₂](AlTi₂)}₁₂+β-{[(Al–Ti_10.5Zr_3.5](Ta_0.75W_0.25Ti_1.5Si_0.5)}₅, featuring equiaxed β grains via Ta replacing Mo/Nb and enhanced additive-manufacturability via Zr replacing Sn. In the as-deposited state, this alloy shows complete equiaxed fine β grains and inner with bimodal basket-weave microstructure, as well as excellent tensile properties (ultimate tensile strength (UTS) of 1312 MPa, yield strength (YS) of 1258 MPa, and elongation of 1.8%). Its 600 °C UTS of 703 MPa, YS of 551 MPa, and elongation of 18%, being comparable to those wrought conventional high-temperature Ti alloys.