Fatigue properties for FSW and MIG welded joints of thickness plate aluminum alloy

The fatigue properties of FSW and MIG welded joints for AA6082-T6 aluminum alloy of 10 mm thickness were investigated by the fatigue S-N curves testing method,and these prperties were also compared to that of AA6082-T6 base material.It was shown that the fatigue S-N curve of AA6082-T6 base material was the highest,the S-N curve of MIG welded joints was the lowest,and the S-N curve of FSW joint was between the two curves.In high stress range,the fatigue strength of FSW was lower than that of MIG welded joints,while in low stress range,it was higher than the MIG welded joints.It indicated that most of the FSW specimens were initially fractured at the weld,caused by the "weak-bonding" defects and the fatigue strength of FSW joint increased apparently,which is close to the values of base material after removing one layer of weld root material with thickness of 1.4 mm.Thus it can be verified that the quality of the weld root sites for the single-side FSW welded joints of AA6082-T6 aluminum alloys thick plate should be the key factor to influence the fatigue properties of FSW joint.