Achievement of defect-free and high-ductility TA5 alloy joint by dynamic supporting friction stir welding

Dynamic supporting friction stir welding (DSFSW) is proposed by developing a novel welding platform. The conventional backing plate is replaced by a small-size supporting column to reduce heat dissipation from weld back in the FSW of titanium alloy. TA5 alloy joints were produced via varied FSW techniques and examinations on macrostructure, microstructure and mechanical properties were carried out. Results reveal that DSFSW enhances material flow by greatly improving the effective heat input into weld, thereby eliminating the flow-related cavity defect. Specifically, DSFSW enables defect-free joint at 250 r/min with a significantly increased welding speed of 55 mm/min (83.3% higher than the conventional FSW). Furthermore, the ductility of joint can be improved more than 20%. Consequently, DSFSW is feasible to obtain high-quality joint of titanium alloy under rather high welding speed.