Effect of Plug Materials on Microstructure and Tensile Fracture Behavior of Aluminum Alloy Friction Plug Welds

Friction plug welding (FPW) experiments were performed on 6mm 2219-T87 aluminium alloy using 2219-T87 and 2A14-T6 plugs. Digital image correlation method was used to determine the deformation and fracture behaviour of FPW joints in tensile process, meanwhile the microstructure, microhardness, and tensile fracture surface of the two FPW joints were observed and tested respectively. The results show that the two joints present similar microstructure, while 2A14-T6 joint exhibits wider partial recrystallized zone in plug thermo-mechanically affected zone than 2219-T87 joint. The plug material has slight effect on ultimate tensile strength, but has a significant effect on the elongation. The tensile strength and elongation of 2219-T87 joint can reach 346. 2MPa and 5. 76%, for 2A14-T6 joint, they are 351. 2MPa, 3. 54%. The deformation mainly concentrates in softening plug thermo-mechanically affected zone and plug metal for 2219-T87 joint, while the deformation concentrates in softening thermo-mechanically affected zone and heat affected zone for 2A14-T6 joint. Recrystallized zone and the softening zone are the weakening zones across the whole joint, and the tensile fracture morphologies are characterized by dimples.