Effect of double annealing treatments on Ti-10V-2Fe-3Al alloy by directed energy deposition

In order to improve the mechanical property of Ti-10V-2Fe-3Al (TB6) metastable β titanium alloy made by directed energy deposition (DED) technique, a group of double annealing treatments were designed. The microstructure and mechanical properties changing after every heat treatment step were systematically investigated. Compared with the traditional solution and aging heat treatment, a microstructure of the fork-like primary α phase (αp) and plate-like secondary α phase (αs) were observed after the new-designed double annealing treatment which the first annealing temperature was below β-transus with the ductility of the alloy increased significantly with slight strength reduction. The optimal tensile properties were obtained by the double annealing treatment with the first annealing temperature above β-transus (820 °C/2 h, AC + 520 °C/8 h, AC).