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

¹ National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin, 150001, China
² School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150001, China
³ National Key Laboratory of Air-based Information Perception and Fusion, Luoyang, 471099, China

^* Corresponding author: wangkehuan@hit.edu.cn

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 (α_p) and precipitation of partial secondary α (α_s). The main stress relaxation mechanisms in the early stage are the precipitation and growth of α_s, stress-induced twinning and the dynamic recovery in α_p. The main stress relaxation mechanisms in the late stage are the globularization of α_s and dislocation recovery in α_p. The strength improvement after stress relaxation is mainly due to the formation of α_s.