Effect of post-weld heat treatment on microstructure and property of linear friction welded Ti17 titanium alloy joint

In this study, post-weld heat treatment of linear friction welded Ti17 (Ti-5Al-2Sn-2Zr-4Mo-4Cr) titanium alloy joints was performed at 530, 610 and 670 degrees C for 4 h followed by air cooling. Results show that with increasing treatment temperature, the recrystallisation extent of the alpha and beta phases in the weld and deformation zones increases significantly. The overall property of the joint is remarkably improved, and the fracture behaviour of the tensile and impact samples changes from brittle failure to a ductile one. After treatment at 670 degrees C, the impact toughness of the joint is 93.3% of the parent metal, and the failure of the tensile samples occurs in the parent metal far away from the weld. According to these findings, a treatment temperature slightly lower than 670 degrees C but higher than 610 degrees C would be a good value for linear friction welding Ti17 joints.