Optimization of welding process and mechanical properties of friction pull plug welded joint on 2219 aluminum alloy sheet

In this paper, the friction pull plug welding process and mechanical properties of 2219 aluminum alloy with 5. 5 mm thickness were studied. Four kinds of plug with different geometrical shapes were designed, and the optimal plug geometry and size were determined through experiments, the plug was circular（R= 50 mm）, the diameter of little end was 32 mm, and the length of conical section was 16. 17 mm.Under the rotation speed of 7 000 r/min, axial tension force of 30 kN and axial feed of 10 mm, defect-free welded joints could be obtained.The microstructure analysis showed that the interface between plug and base material was good, and the grains on the side of the base material adjacent to the interface had dynamic recrystallization, and the grains in the thermal-mechanical affected zone were elongated along the extrusion direction of the plug. The orthogonal test and analysis results showed that among the three main welding parameters such as rotation speed,axial tension force and axial feed, the rotation speed, had the greatest influence on the tensile strength of the joint, the axial tension force was the second, and the axial feed was the least. When the rotation speed reached more than 7 000 r/min, the tensile strength of the joint could be improved by increasing the axial tension force. The highest tensile strength of the joint obtained in this paper could reach 357 MPa, which was equivalent to 76. 7% of the base material. Under the condition of good bonding interface, the tensile fracture location of the joint was the thermal-mechanical affected zone, and the fracture surface showed toughness characteristics.