Abstract: As-deposited TB18 titanium alloy was prepared by using BLT-C1000 laser solid forming equipment, and then the effects of different heat treatment processes on microstructure and mechanical properties of the TB18 titanium alloy were studied by means of OM, SEM and tensile testing machine. The results show that the macrostructure of the as-deposited tested alloy is dominated by elongated β grains, which are composed of metastable β phases and acicular secondary α phases, and there are deposited layer lines running through the β-grains. With the increase of direct aging temperature, the shape of the original β grains changes a little, the thickness of the internal secondary α phases increases, and the morphology of secondary α phases changes from needle-like to flake-like. When the direct aging temperature is higher than 550 ℃, the deposition layer line disappears, and the microstructure is composed of all β grains at the direct solution temperature higher than 830 ℃. After solution and aging treatments, the microstructure mainly consists of crisscross fine lamellar secondary α phase. With the increase of direct aging temperature, the tensile strength and yield strength decrease and the elongation increases. The secondary α phase is precipitated after solution and aging treatments, and the tensile strength and yield strength increase significantly, while the elongation decreases. By comprehensive consideration, the optimal heat treatment process of the as-deposited TB18 titanium alloy in actual production is direct aging at 500 ℃ for 4 h, at which the strength and elongation are higher than the index requirements.

Key words: laser solid forming, TB18 titanium alloy, heat treatment, microstructure, mechanical properties