Microstructure and properties of 6061 aluminum alloy welded joint by FSW

Friction stir welding was carried out on 6061 aluminum alloy with a thickness of 6 mm. Metallographic structure, fracture morphology, tensile property and corrosion property of welded joints were tested and analyzed by optical microscope, scanning electron microscope, tensile testing machine and electrochemical workstation, respectively. The results showed that when the welding speed was 80 mm/min and the rotation speed was between 600～1 500 r/min, the welded joint had a good appearance without obvious defects. With the increase of rotation speed, the grain size of the welding nuclear zone decreased first and then increased. When the rotation speed was 1 200 r/min, the grain size of the welded core area was the smallest, and the tensile strength and elongation of the welded joint were the highest, 168 MPa and 14.7%, respectively. The weld strength reached 81.9% of base metal. The fracture mode of the welded joint was ductile-brittle mixed fracture mode, which was mainly ductile fracture. With the increase of rotation speed, the corrosion resistance of FSW joint first increased and then decreased. When the rotation speed of FSW joint was 1 200 r/min, the corrosion resistance of FSW joint was the best, and the minimum self-corrosion current density of FSW joint was 2.4×10-5 A/cm2.Highlights: The relationship between welding parameters and the corrosion resistance of friction stir welded joint was studied.