Effect of welding speed on material flow, microstructure and mechanical properties of BT-FSW 2219 aluminum alloy joints

The influence of welding speed on material flow, microstructure and mechanical properties of bobbin-tool FSW (BT-FSW) joints was analyzed by numerical simulation and experimental method on 2219-T87 aluminum alloy with the thickness of 4 mm. The simulation results show that the high-temperature zone of the joint became narrower with the increase of welding speed. The material flow near the shoulder was weakened, while the material flow near the pin was enhanced. The experimental results show that with the increase of welding speed, the material confluence zone and S line defects were closer to the advancing side (AS). However, the stirring zone (SZ) on the AS formed a discontinuous structure when the welding speed was too high. The hardness of SZ increased with the increase of welding speed, while the tensile strength increased first and then decreased slightly. When the welding speed was 150 mm/min and the rotation speed was 300 rpm, the maximum tensile strength of the joint was 414 ± 4 MPa.