Microstructure and mechanical properties of friction pull plug welding for 2219-T87 aluminum alloy with tungsten inert gas weld

The friction pull plug welding (FPPW) of the 2219-T87 tungsten inert gas (TIG) welded joint was investigated, and the microstructures, precipitate evolution, mechanical properties, and fracture morphologies of this joint were analyzed and discussed. In this study, defect-free joints were obtained using a rotational speed of 7000 r/min, an axial feeding displacement of 12 mm, and an axial force of 20–22 kN. The results indicated that within these welding parameters, metallurgical bonding between the plug and plate is achieved by the formation of recrystallized grains. The microstructural features of the FPPW joint can be divided into different regions, including the heat-affected zone (HAZ), thermomechanically affected zone (TMAZ), recrystallization zone (RZ), heat-affected zone in the TIG weld (TIG-HAZ), and the thermomechanically affected zone in the TIG weld (TIG-TMAZ). In the TIG-TMAZ, the grains were highly deformed and elongated due to the shear and the extrusion that produces the plug during the FPPW process. The main reason for the softening in the TMAZ is determined to be the dissolution of θ′ and coarsening of θ precipitate particles. In a tensile test, the FPPW joint welded with an axial force of 22 kN showed the highest ultimate tensile strength of 237 MPa. The locations of cracks and factures in the TIG-TMAZ were identified. The fracture morphology of the tensile sample showed good plasticity and toughness of the joints.