Refill friction stir spot welding of 5083-O aluminum alloy

In this work, refill friction stir spot welding (RFSSW) was used to weld 2 mm-thick 5083-O alloy. The Box–Behnken experimental design was used to investigate the effect of welding parameters on the joint lap shear property. Results showed that a surface indentation of 0.3 mm effectively eliminated the welding defects. Microhardness of the stir zone (SZ) was higher than that of the base material (BM) and the hardness decreased with increasing the heat input during welding. The optimum failure load of 7.72 kN was obtained when using rotating speed of 2300 rpm, plunge depth of 2.4 mm and refilling time of 3.5 s. Three fracture modes were obtained during the lap shear test and all were affected by the hook defect.