关键词: 去应力退火, 钛合金, 力学性能, 显微组织, 残余应力

Abstract: Effect of stress relief annealing at 480 ℃ and 500 ℃ on mechanical properties, residual stress and microstructure of Ti-4Al-5Mo-5V-6Cr-1Nb titanium alloy was investigated. The results show that stress relief annealing has a relatively small effect on strength. After stress relief annealing, the tensile strength remains around 1310 MPa and the yield strength remains around 1250 MPa. After stress relief annealing at 480 ℃, the percentage reduction of area is reduced by 17.8% and the fracture toughness is reduced by 8.8%. When the stress relief annealing temperature increases to 500 ℃, the percentage reduction of area and fracture toughness are basically the same as those without stress relief annealing. The microstructure changes a little after stress relief annealing, with straight α phases at grain boundaries and interlaced network distribution of α phases within the grains. The tensile fracture mechanism of the alloy before and after stress relief annealing is a mixed fracture mechanism of ductile dimples and quasi cleavage. The fiber zone area after stress relief annealing at 480 ℃ is significantly smaller than that without stress relief annealing and at 500 ℃. Stress relief annealing at 500 ℃ for 1 h can effectively eliminate residual stress of the alloy. Considering the comprehensive residual stress, strength, plasticity, and fracture toughness, the stress relief annealing process at 500 ℃ for 1 h should be selected.

Key words: stress relief annealing, titanium alloy, mechanical properties, microstructure, residual stress