关键词: 近α型钛合金, 退火, 冷却速度, 残留β相, 力学性能

Abstract: Annealing cooling rate of Ti80 alloy was regulated by controlling the cooling method, and aging treatment was performed on the air-cooled alloy with the minimum cooling rate. The transformation behavior of the residual β phase and its influence on mechanical properties were systematically investigated with a constant volume fraction of equiaxed α phase. Microstructural and mechanical characterizations were conducted by using optical microscope, scanning electron microscope, universal testing machine and Rockwell hardness tester. The results indicate that the volume fraction of the primary α phase remains equivalent under different cooling rates. After high-temperature annealing and water cooling, the residual β phases appear as isolated island-like structures. With cooling rate decreasing, the β phases preferentially transform at grain boundaries, forming a dispersed morphology. The decomposition of the residual β phase intensifies after aging. In terms of mechanical properties, the alloy exhibits maximum strength and hardness under water cooling condition. As the cooling rate decreases, both strength and hardness decline significantly, while plasticity shows a slight improvement. These findings highlight the critical role of residual β phase decomposition in determining the mechanical behavior of the Ti80 alloy, namely, higher cooling rates enhance strength, whereas lower cooling rates improve plasticity.

Key words: near-α titanium alloy, annealing, cooling rate, residual β phase, mechanical properties