Assessment of Fatigue Life of Gas Metal Arc and Friction Stir Welded AA 6061-T651 Aluminium Alloy Joints: A Comparative Investigation

In this study, AA6061-T651 Aluminium alloy was joined by gas metal arc welding (GMAW) and friction stir welding (FSW) processes. Both joints were compared and discussed in terms of their microstructure and fatigue properties. The microstructural evolution of the weldment was examined using optical microscopy (OM) and orientation image microscopy (OIM). FSW joints have finer grains than GMAW joints, which results in higher hardness. In GMAW and FSW joints, the tensile strength was 195 MPa and 230 MPa, respectively. This is 62% and 74% of the base metal. A fully reversible fatigue testing machine was used to investigate the fatigue properties of both joints. In comparison with GMAW joints, FSW joints have significantly better fatigue properties and reach infinite life at 90 MPa. Fractographic analysis shows that FSW joints had fewer crack initiation sites in stage I and better crack growth resistance in stage II than GMAW joints.