Friction Stir Welding of Aluminium High Pressure Die Castings: Parameter Optimisation and Gap Bridgeability

It is well established that friction stir welding (FSW) allows joining of aluminium alloys which can hardly be fusion welded. A well-known limitation of weldability in aluminium alloys is high hot crack sensitivity, such as encountered in Al-Cu and Al-ZnMgCu alloys. The weldability of cast alloys containing a significant amount of gases with MIG, TIG or laser welding is however also significantly compromised due to the occurrence of porosity, blowholes and cracks in the fused metal. In this study, the high pressure die cast aluminium alloy EN AC-46000-F, which belongs to the latter category of alloys with strongly reduced weldability, is successfully joined with the FSW technique. The selection of optimum welding conditions is discussed as function of the tensile properties and salient microstructural features. Moreover, the gap bridging ability of the FSW process is highlighted, by demonstrating the influence of weld gap on joint strength and the occurrence of weld flaws.