Microstructures and Properties of Friction Stir Welded Joint of 6061-T6 Aluminum Alloy

Aluminum alloy 6061-T6 in thickness of 4 mm was welded by friction stir welding (FSW). The microstructure, mechanical property and corrosion property of FSW joint were investigated by optical microscopy, tensile test and static weight loss experiment. The results demonstrate that the weld nugget zone (WNZ) was characterized by the dynamic recrystallization, which consisted of refined equiaxed grains. The grains in thermo-mechanically affected zone (TMAZ) highly deformed and those in heat-affected zone (HAZ) coarsened. When the welding rate was 160 mm·min-1, the peak tensile strength of the joint reached 215 MPa as much as 76% of the base metal, and the joint fractured as a mode of ductile fracture. Micro-hardness of the joint distributed as W shape and was symmetrically along the welding line. The micro-hardness of the HAZ on advancing side was lower than that of the base metal, where should be the weak zone of the welded joint. The corrosion property of the weld was better than that of the base metal at a welding rate of 160 mm·min-1.