Microstructures and properties of 2219-T87 aluminum alloy friction pull plug welds

Friction pull plug welding (FPPW) experiments were performed for 6mm thick 2219-T87 aluminum alloy. The microstructures, microhardness, tensile strength and tensile fracture surface of FPPW joints were observed and tested respectively. It is verified that metallurgical combination was realized between 2219-T87 plate and 2219-T87 plug using optimized FPPW process. In FPPW process, plug was subjected to tensile stress. Joint design and welding parameters are optimized to prevent plug from being broken off. Lack of bonding was the main defect for FPPW joint, which was easily formed near the upper surface. Softening was observed in the weld zone, the minimum hardness (84.4 HV) appeared in plug thermo-mechanical affected zone. The tensile strength and elongation of FPPW joint can reach to 326.4 MPa and 4.45%, which are equivalent to 71.7% and 44.5% of the base metal. The tensile fracture morphologies are characterized by dimples.