Microstructure and property of laser additive manufactured alloy Ti–6Al–2V–1.5Mo–0.5Zr–0.3Si after aged at different temperatures

The solid solution and aging treatment for conventional manufacturing processes might not be suitable for laser additive manufactured titanium alloys due to the different lamellar microstructures. In this study, the influence of aging temperatures (600, 700 and 800 °C) on microstructure and mechanical properties of titanium alloy Ti–6Al–2V–1.5Mo–0.5Zr–0.3Si was investigated. The results indicate that after solid solution treatment at 970 °C followed by water quenching, the alloy mainly consists of coarsening lamellar α phase in martensite α′ matrix. Aging at 600 °C will not change the size of primary lamellar α phase but lead to huge amount of secondary α phases (α_s) generating with very fine microstructure. By increasing the aging temperature, the number of α_s decreases but with coarsened microstructures. When aged at 800 °C, the width of the α_s phase reaches 350 nm, almost 7 times wider than that aged at 600 °C. The changing size of α_s obviously influences the property of the alloy. The fine α_s leads to high strength and microhardness but low plasticity, and specimen aged at 700 °C with suitable α_s size has the best comprehensive properties.