Fatigue Behavior of Dissimilar Al-Mg-Si/Al-Zn-Mg Aluminum Alloys Friction Stir Welding Joints

In this study, fatigue properties and fracture mechanism of dissimilar Al-Mg-Si/Al-Zn-Mg aluminum alloys friction stir welding （FSW） joints were investigated and the effect of the sheet configuration on the fatigue behavior of the FSW joints was also discussed. Results showed that the joints owned better fatigue properties when the Al-Zn-Mg aluminum alloy was placed at the advancing side （AS）. At 107 cycles, the fatigue strengths of Al-Zn-Mg-AS and Al-Mg- Si-AS joints were, respectively, 105.6 and 90.1 MPa. All joints fractured at the heat-affected zone at the Al-Mg-Si alloy side. Transmission electron microscopy results showed that better fatigue property of the Al-Zn-Mg-AS joint was associated with the bridging effect of the bigger secondary phase particles.