Refill Friction Stir Spot Welding Parameter Optimisation for Transport Industry Aluminium Alloys
By Pedro Santos (TWI,Ltd), Anthony Mcandrew (TWI,Ltd), João Gandra (TWI,Ltd), Bilal Ahmad (Coventry University), Xiang Zhang (Coventry University)

Refill friction stir spot welding (RFSSW) is a solid-state spot-joining process, which offers many advantages for joining aluminium alloys in the transport industry. In this investigation, RFSSW was used to produce solid-state welds in 2 mm thick AA5754-H24, AA2024-T3 and AA7075-T6 aluminium alloys. A range of values for rotational speed (RS) and plunge depth (PD) were evaluated to determine their effects on the weld microstructure and shear strength. The results show that lower RS and higher PD values improve the shear strength of the weld, which was attributed to the increase of the welded area and grain refinement. Fatigue life analysis, SEM fractography and residual stress measurements via contour method were then further evaluated for the most promising process parameter combination of each material. These findings demonstrate the potential of RFSSW to enable industrial implementation for lightweighting applications.