Effects of heat treatments on microstructure and mechanical properties of TC4 titanium alloy thick plate

The effect of different heat treatments on microstructure and mechanical properties of TC4 titanium alloy thick plate was studied by means of orthogonal testing method. The results show that the solution temperature greatly affect on microstructure,strength,plasticity and fracture toughness of the alloy. When the alloy is treated with solution treatment below beta transus temperature,there is bimodal microstructure. When the alloy is treated with solution treatment above beta transus temperature,there is widmanstatten microstructure. With the increase of solution temperature from 975 ℃ to 1045 ℃,strength little changes,plasticity significantly reduces,while fracture toughness gradually increases. TC4 titanium alloy thick plate exhibits optimum strength and plasticity when solution treated at 975 ℃ for 10 min and aging at 670 ℃ for 1 h,exhibits optimum strength and fracture toughness when solution treated at 995 ℃ and aging at 670-760 ℃.