Failure modes and fatigue behavior of conventional and refilled friction stir spot welds in AA 6061-T6 sheets

• AA 6061-T6 sheets are successfully welded and refilled by FSSW-FFP using filler plate.
• Different modes of fracture observed in conventional FSSW and FSSW-FFP weld samples.
• Better fatigue properties can be obtained by the FSSW-FFP process at all loading conditions.

The fatigue behavior of conventional friction stir spot welding (FSSW) and friction stir spot welding refilled by the friction forming process (FSSW-FFP) in aluminum 6061-T6 lap shear specimens, are investigated based on the experimental observations. Optical micrographs of the welds after fatigue failure in both the cases are examined to study the fatigue crack propagation and failure modes. Experimental results indicate that the fatigue strength of the FSSW-FFP weld samples is higher than that of the conventional FSSW samples at all loads. Fracture surfaces are analyzed in detail using the scanning electron microscope.