Abstract: TC21 titanium alloy block was prepared by the BLT-C1000 laser three-dimensional forming equipment, and the single-stage and two-stage annealing treatments were carried out, respectively. The influence of the single-stage and double-stage annealing processes on microstructure and mechanical properties of the alloy was studied. The results show that the deposited structure of TC21 titanium alloy by laser solid forming is mainly a basket-like microstructure. The single-stage annealing temperature affects the size of the primary α-phase slats. When annealed below 550 ℃, the length and width of the primary α-phase slabs change slightly. When annealed above 650 ℃, the length and width of the primary α-phase slabs increase significantly and the width will be slightly reduced. With the increase of heating temperature, the yield strength and tensile strength is decreased, while the elongation and reduction of area after fracture is increased. During double-stage annealing, with the increase of the first-stage annealing temperature, the amount of primary α phase is decreased, with the increase of the second-stage annealing temperature, the size of the secondary α phase is increased. Considering comprehensively, the first-stage annealing temperature of 870-900 ℃ and the second-stage annealing temperature of 560 ℃ are optimal for double-stage annealing.

Key words: laser solid formed TC21 titanium alloy, annealing treatment, microstructure, mechanical properties