In this research, two methods of conventional Friction Stir Welding (FSW) and two-pass friction stir welding have been used to weld AA6061-T6 alloy parts with a copper interlayer (copper foil. Based on the results, it was determined that the number of welding passes, the presence or absence of copper foil as an interlayer, the number of welding passes, the direction of tool rotation and the direction of tool movement in the second pass strongly affect the strength and ductility of FSW. According to the results, the highest tensile strength and ductility belong to TP-D(Two-Pass, type D), TP-B(Two-Pass, type B), TP-C(Two-Pass, type C), TP-A(Two-Pass, type A), CF-Cu and CF(Conventional FSW) samples, respectively. The mentioned samples have growth of 21, 29, 45, 36 and 58% respectively compared to the CF sample. The highest strength growth was related to the TP-D sample, which experienced a 58% increase in tensile strength compared to the CF sample. The tensile strength efficiency of this sample is 89.3% compared to the base metal. The highest increase in ductility was related to the TP-D sample, which experienced a 35% increase in ductility compared to the CF sample. The ductility efficiency of this sample is 81.1% compared to the base metal. پرونده مقاله