Study on Process of 6061-T6 Aluminum Alloy Stationary Shoulder Friction Stir Welded Joints

6061-T6 aluminum alloy sheets with 3 mm thickness were welded by robot stationary shoulder friction stir welding technology. The actual working conditions were simulated by presetting tool offset and the joint gap under the fixed welding parameters of 3000 r/min, 1500 mm/min and inclination angle of 2°. The effects of different parameters on the weld forming, joint microstructure and mechanical properties were investigated by microstructure analysis and mechanical properties testing. The results show that the welded joints with high strength can be obtained by tool offsetting to retreating side. When the gap is 0.2, 0.4 mm, the tensile strength of the welded joints can reach more than 70% of the base material, and when the gap is 0.6 mm, tunnel defects are found in the welded joints.