Study on the stress relaxation with synchronous ageing of near α titanium alloy

Abstract

The stress relaxation with synchronous ageing of TA15 titanium alloy was studied under a plastic pre-loading condition. The evolutions of microstructure and room temperature properties were characterized. Results show that the stress can be eliminated by 85 %, and the ultimate tensile strength can be increased by 5 % compared to the as-received sheet at room temperature. The plastic pre-loading results in dislocation entanglements in primary α (αp) and precipitation of partial secondary α (αs). The main stress relaxation mechanisms in the early stage are the precipitation and growth of αs, stress-induced twinning and the dynamic recovery in αp. The main stress relaxation mechanisms in the late stage are the globularization of αs and dislocation recovery in αp. The strength improvement after stress relaxation is mainly due to the formation of αs.