Effect of incomplete penetration defects on mechanical and fatigue properties of friction-stir-welded 6802-T6 joint

Abstract In this study, 6802-T6 alloy plates were welded using tools with different pin lengths. Different depths of incomplete penetration defects, including kissing bond (K) defect and remain joint surface (R) defect, were obtained. Mechanical fracture and kernel average misorientation (KAM) maps indicated that joint root tearing caused K defect during the friction stir welding (FSW) process. The critical value for incomplete penetration geometry appeared to be a depth of 0.4 mm. Within this interval, the ultimate tensile strength of the joint (thickness of 3 mm) was more than 224 MPa, and the fatigue strength exceeded 70 MPa at 107 cycles.