Effect of Post Weld Heat Treatment on Residual Stress and Mechanical Properties of 106 mm Thick TC4 Titanium Alloy Electron Beam Welded Joints

This study analyzed through-thickness distribution of residual stress in a 106 mm ultra-thick TC4 titanium alloy electron beam welded (EBW) joint after post weld heat treatment (PWHT) using X-ray diffraction (XRD) and deep-hole drilling (DHD) methods, and investigated the microstructure and mechanical properties. During the PWHT at 600 °C, a phase transformation (β → α) occurred in the EBW joint and affected the residual stress distribution and mechanical properties. The surface residual stress was mainly compressive stress, while the internal residual stress was mainly tensile stress in the welded joint. For the as-welded joint, the absolute value of surface residual stress was higher than the absolute value of internal residual stress. After PWHT, the residual stress in the treated joint was substantially reduced compared to the as-welded joint, particularly the surface stress, which relieved from − 425 to − 90 MPa. However, the residual stress relief effect had minimal positive impact on the internal region at 600 °C. PWHT resulted in a shift of the joint fracture location from the fusion zone (FZ) to the base metal (BM), and therefore exerted no noticeable effect on the joint strength, but increased the joint elongation significantly. This study provides valuable insights into the regulation of residual stress distribution of ultra-thick titanium alloy plates.