铝/钛异种合金回填式搅拌摩擦点焊接头的微观组织与力学性能

2 mm thick 5A02 aluminum and TC4 titanium dissimilar alloy plates were bonded by refill friction stir spot welding. The effects of different process parameters on the microstructure and mechanical properties were investigated by changing dwell time and refilling speed. Results show that within the selected process parameters, the sound joints are formed by the unthreaded stirring tool. The fine grains are produced in the stir zone and the grains in the heat affected zone are limited to satisfying extent. The atomic diffusion distance at the interface of the sleeve affected zone is larger than that in the pin affected zone. The atomic diffusion distance at the interface of the joint is about 2 gm when dwell time is 6 s. With the increasing of the refilling speed, the tensile shear load of the joint increases basically. The thickness of interfacial reaction layer decreases and the grains in the joint are refined. The minimum tensile shear load is 4861 N at the refilling speed of 0.5 mm/s and dwell time of 6 s. The pull out fracture morphology is observed and dimples are found locally. When the refilling speed is 1.5 minis and dwell time is 6 s, the tensile shear load reaches the maximum of 6617 N. The interface fracture mode is observed while the macroscopic fracture surface is relatively flat. The microscopic fracture is consisted of dimples.