Microstructure and mechanical properties of laser deposition manufactured a newly developed Ti-6Al-2Mo-2Sn-2Zr-2Cr-2V titanium alloy

Abstract

With the rapid development of aviation industry, the study of new type titanium alloy with superior mechanical properties is of great significance. In this paper, a newly developed Ti-6Al-2Mo-2Sn-2Zr-2Cr-2V (Ti-622222) alloy was fabricated by laser deposition manufacturing (LDM). The as-deposited Ti-622222 alloy exhibits coarse β columnar grains containing the basket-weave structure knitted with α phases and β phases. The solution and aging treatment decreases the size and content of primary α phase, but promotes the precipitation of secondary α phase. The microhardness shows a rising trend with the solution temperature increasing due to the precipitation of fine secondary α phase. The LDMed Ti-622222 alloy exhibits superior tensile strength (1025 MPa) and inferior elongation (6.0%). With the solution temperature increasing, the strength increases but the plasticity first increases and then decreases. The LDMed Ti-622222 alloy exhibits a mixed fracture mechanism of ductile and brittle fracture. The LDMed Ti-622222 alloy exhibits obvious anisotropy of impact property, the average impact toughness of the as-deposited sample in scanning direction is 23.4 J/cm2 lower than that (40.9 J/cm2) in deposition direction. After solution and aging treatment, the impact toughness improves significantly. With the solution temperature increasing, impact toughness first increases and then decreases.