Performance Evaluation of 2-mm Thick Alclad AA2024 T3 Aluminium Alloy Friction Spot Welding 2007-01-3812

Friction spot welding (FSpW) is a solid-state joining process suitable for welding lightweight materials e.g. aluminium and magnesium alloys for structural applications. The FSpW process is performed by plunging a rotating tool (consisting of a pin and a shoulder) into the workpiece producing frictional heat on the upper sheet surface; both pin and shoulder are moved in opposite direction to each other; plastified material is squeezed into an annular space left by the pin; the shoulder retracts back towards the surface of the plate while the pin keeps moving towards the plate pushing the material that was originally displaced back into the plate. Contrary to the friction stir spot welding process, there is no keyhole left at the end of the joining operation. FSpW has been performed in an alclad AA2024 T3 aluminium alloy using different parameters (shoulder plunge depth, shoulder plunge and retract rotational speed) aiming to produce high quality welds with good microstructural and mechanical properties. Mechanical performance has been investigated in terms of shear and cross-tension testing. Preliminary results have shown that an increase in shoulder plunge and retract rotational speeds had a detrimental effect on the mechanical properties. Volumetric defects have been found; therefore further process optimisation is needed.