Thermo-Mechanical Study of TIG Welding of Ti-6Al-4V for Residual Stresses Considering Solid State Phase Transformation

Abstract

To overcome the detrimental effect of residual stress in welded joints, which affects the overall performance of the welded structure, this paper studies the magnitude and distribution of residual stress after welding and local post-weld heat treatment (PWHT). The coupled thermo-metallurgical-mechanical model for welding 6 mm thick Ti-6Al-4V (TC4) titanium alloy plates was established, the evolution of the SSPT and its effect on the residual stress were quantitatively analyzed, and a parametric analysis of local PWHT was performed. The results demonstrated that there was good agreement between the numerical results and the experimental data. Due to the cooling rate reaching 327 °C/s, the volume fraction of α、 in the fusion zone (FZ) reached 0.218 after welding and decreased by 90.83% after PWHT when the heating temperature was 700 °C. The peak value of the longitudinal residual stress can reach 686.4 MPa after welding with SSPT, which was 11.38% lower than that without SSPT, and it decreased by 65.6% after PWHT when the heating temperature was 900 °C. The research results demonstrate that SSPT has a significant effect on residual stress, and PWHT can obviously reduce the residual stress, which provides a certain reference for welding TC4 titanium alloy plates.