LAUSR

Abstract To improve the degree of materials mixing in dissimilar Friction Stir Welded (FSW) joints and mechanical properties, a novel stirring tool with dual-pin structure was designed and used to perform welding AA 2024 to AA6061 aluminum alloy plates with butt configuration. The microstructure and mechanical properties of the joints fabricated by single-pin and dual-pin tools were studied using optical microscope (OM), scanning electron microscope (SEM), microshardness tester and tensile testing machine. It was found that joints produced by dual-pin tool were all free of defects throughout the selected parameters, but for the joints produced by single-pin welded joints, void defects were produced at welding speed higher than 90 mm/min. All the nugget regions of dual-pin joints were characterized by typical onion ring patterns which were absent in those obtained by dual-pin tool. The highest ultimate tensile strength (UTS) of 242 MPa was obtained with the dual-pin tool at welding speed of 150 mm/min, while for the case of single-pin the best joint was obtained at welding speed of 90 mm/min. For the defect free joints, those produced by dual-pin tool showed more uniform microhardness distribution over the cross section of joints than the ones produced by single-pin tool.