Effect of tool rotation speed on mechanical properties of underwater friction stir welding of 6061-T6 and 5083-H12 aluminium alloys

Abstract

This work presents an experimental investigation of the effect of tool rotation on the mechanical properties of 6061-T6 and 5083-H12 aluminium alloys in the UFSW weld joint. The experiments are conducted in a vertical milling machine (model no. HMT FN2H) at four different tool rotation speeds (TRS), such as 710, 900, 1120, and 1400 rpm, at constant welding speed (WS) of 63 mm/min. The welding was performed under the water in the butt joint configuration in which the 6061-T6 workpiece material is placed on the retreating side (RS) and 5083-H12 on the advancing side (AS). The results show that the performance of the weld joint quality depends on the TRS. The shape and size of the weld nugget zone (WNZ) and thermo-mechanically affected zone (TMAZ) increase with increasing the TRS. The tensile strength of the weld joint and average grain size of the stir zone (SZ) increases and decreases respectively on increasing the TRS 710 to 1120 rpm. Further increasing the TRS, the tensile strength of the weld joint and average grain size of SZ decreases and increases respectively. Additionally, the fracture surface shows the brittle dominance fracture mode at 1400 rpm, and 710 to 1120 rpm weld joints show the ductile fracture mode.