关键词: Ti31钛合金, 增材制造, 热处理, 显微组织, 力学性能

Abstract: Effect of heat treatment on the microstructure and mechanical properties of the additive manufactured T31 titanium alloy was investigated by means of scanning electron microscope, electron backscatter diffraction, X-ray diffractometer, tensile testing machine and impact testing machine. The results indicate that the microstructure of the as-deposited Ti31 titanium alloy is acicular martensite. After annealing at 800 ℃ followed by furnace cooling, the microstructure is composed of fine strip-like α phase and a small amount of bulk α phase. After annealing at 800 ℃ followed by air cooling, the microstructure is fine strip-like α phase. The microstructure of the alloy annealed at 900 ℃ followed by air cooling consists of fine lath-like α phase and a small amount of equiaxed α phase, while the microstructure after dual heat treatment of annealing at 900 ℃ followed by air cooling and annealing at 800 ℃ followed by air cooling comprises lath-like α phase and partial equiaxed α phase. All alloys subjected to different heat treatments exhibit texture of the same orientation, with the maximum texture intensity observed in the [0001] basal plane. With the increase in number of heat treatments and decrease in cooling rate, the tensile strength of the SLM Ti31 titanium alloy decreases; with the increase in heat treatment temperature and number of heat treatments, the elongation of the alloy improves. The SLM Ti31 titanium alloy annealed at 800 ℃ followed by furnace cooling exhibits poor impact property due to the formation of bulk α phase. After annealing at 800 ℃ followed by air cooling, the tensile strength of the SLM Ti31 titanium alloy can reach 840 MPa, with an elongation of 20.3% and an impact absorbed energy of 75.9 J, demonstrating the optimal comprehensive mechanical properties.

Key words: T31 titanium alloy, additive manufacturing, heat treatment, microstructure, mechanical properties