Effect of friction-stir welding on the microstructure and mechanical properties of an Al-Mg-Si alloy

In this work, sheets of an Al-Mg-Si alloy were joined by double-side friction stir welding and tempered by standard post-weld artificial aging. The combination of relatively high FSW tool rotation and welding speed with subsequent post-weld artificial aging allowed obtaining welds with high joint efficiency. However, a high sensibility of joint efficiency from FSW tool rotation speed at constant welding speed was found. In turns, the joint efficiency of the friction-stir welds for ultimate tensile strength was found to be 72% at 800 rpm and 92% at 1100 rpm, respectively. The reasons of difference in the mechanical properties of the welds are studied. (paper)