Abstract: Recrystallized grain growth behavior of the cold-rolled Ti-3.5Al-5Mo-4V alloy after annealing at 800-1020 ℃ for 15 min was studied by means of X-ray diffractometer, optical microscope and scanning electron microscope. The effects of grain size on mechanical properties and aging precipitation were also investigated. The results show that with the increase of annealing temperature, the grains grow rapidly, and the tensile strength and elongation of the alloy at room temperature decrease. The activation energy of grain growth is 84.949 kJ/mol, and the relationship between grain size and temperature is D=400 312exp(-84 949/RT). After annealing at 800 ℃ and aging at 500 ℃ for 8 h, the microstructure of the cold-rolled sheet is fine equiaxed β grains uniformly distributed with needle-like secondary α phase. The tensile strength of the alloy reaches 1530.0 MPa, while the elongation remains 5.5%.

Key words: Ti-3.5Al-5Mo-4V alloy, heat treatment, grain growth, aging, mechanical properties