Abstract:Friction stir welding (FSW) of aluminum alloys is currently utilized in several modern industries. The joints must have sufficient elastic-plastic response and formability levels similar to that of the base metal. In this work, double-sided FSW of AA6061 sheet was compared with its conventional single-sided one. An adjustable tool with different pin lengths (50%-95% of the sheet thickness) was used to perform the double-sided welds. Macro- and micro-structures, strength, and hardness of the joints were investigated to determine the optimum pin penetration depth. The best results were obtained for a double-sided joint made by a pin length equal to 65% of the sheet thickness, which showed an increase of 41% in the ultimate tensile strength compared with the single-sided joint.

Key words: AA6061 aluminium alloy; friction stir welding; double-sided joint; pin length; mechanical properties; microstructure