Effects of supporting plate hole and welding force on weld formation and mechanical property of friction plug joints for AA2219-T87 friction stir welds

Friction plug welding (FPW) experiments were performed on 8-mm-thick 2219-T87 FSW welds to investigate the weld formation, microstructure, hardness distribution, mechanical property, and fracture behaviors of FPW joint. The main findings are as follows: geometric size of supporting plate hole and welding force exert great effect on weld formation and mechanical property. Recrystallized zone (RZ) with varied width is observed on the bonding interface between the plug and base metal due to huge friction heat and deformation. Softening is found near the bonding interface due to the disappearance of cold working and transformation of constituent particles. The ultimate tensile strength (UTS) and elongation of FPW joint can reach 336.3MPa and 8%, respectively. The initial fracture of tensile specimen is prone to locate at the lower part of RZ. The tensile fracture morphology of FPW joint is characterized by dimples.