Investigated on the non-uniformity of AA6056 bobbin tool friction stir welding joint

6056 aluminum alloy with 4mm thickness was welded by bobbin tool friction stir welding, and the non-uniform characteristics of microstructure and mechanical properties of different characteristic areas of the joint were studied. Results show that the equivalent strain of the cross section of the joint is dumbbell shape, which is consistent with the macro-morphology of the cross section of the weld. The plastic strain distribution along the left and right sides of the weld center is asymmetrical, and the plastic strain value at the advancing side of the joint is higher than that at the retreating side. The proportion of high angle grain boundary near the advancing side and the middle side is higher than that on the retreating side. The advancing side and middle side are mainly B-type $\{1 \overline 1{2}\}$<110> texture, and the retreating side is A-type $\{11 \overline{1}\}$<110> texture. Incomplete dynamic recrystallization occurs in the band pattern area of the weld, and the proportion of deformed grains is 58.9%. The band pattern area is B-type $\{11 \overline {2}\}$<110> texture with texture strength of 10.6, which is higher than that of other positions in the stir zone. The strain in the heat affected zone is more than 18%, which is higher than the whole joint with 3.6%. The strain in the thermo-mechanically affected zone is similar to that of the whole joint, while the strain in the stir zone is less than that of the whole joint.