The Influence of Weld Microstructure on Mechanical Properties of Alclad AA2024-T3 Friction Spot Welded 2008-01-2287

Friction Spot Welding – FSpW, also known, as Refill Friction Spot Welding is a new solid-state spot process developed by GKSS, exhibiting as one of the main advantages, no key-hole on the surface of the material after the completion of the process. In the present work FSpW has been performed in 2 mm-thick Alclad AA2024-T3 varying tool rotational speeds, sleeve plunge depths in lower sheet and plunge rates. Mechanical properties of the connections have been investigated in terms of hardness and shear testing. The fracture mechanisms were observed by SEM and the microstructural features by OM. The results have demonstrated that the optimum tool rotational speed is dependent on the other welding parameters as plunge rate and plunge depth. Plunge depths of around 25% (0.5 mm) of bottom plate thickness have proved to be adequate to reach a good mechanical performance of the connections. It was observed that the main feature affecting the mechanical properties of the joint is the Alclad distribution inside the weld. Furthermore, lower plunge rates have resulted in more homogeneous distribution of the Alclad and thus, in better mechanical performance of the connections.