Experimental investigation on mechanical properties affected by dissimilar friction stir spot welding of aluminum 6061-T6 alloy to copper

Friction stir spot welding (FSSW) is one of the types of solid state welding methods for joining parts and light metals, especially aluminum and copper alloys. In this research, the effect of important parameters of the FSSW welding process, such as rotational speed and tool stop time, on the mechanical and micro- hardness properties of dissimilar connections of aluminum alloy 6061 to commercial pure copper has been investigated. Also, the effect of the placement of the sheets on the mechanical properties has been studied. The results show that by increasing the rotational speed of the tool from 1250 to 1600 rpm and the stopping time of the tool from 5 to 10 seconds, the tensile and bending strength of all welded samples increases. Also, at rotational speeds less than 1250 rpm due to the reduction of frictional heat generation, and higher than 1600 rpm due to excessive heat generation, the quality of connections has decreased. The results of micro- hardness measurement show that in various welding parameters, increasing the rotational speed and stopping time of the tool caused the creation of fine grains and recrystallization found in the stir zone and other areas, which is due to the heat produced due to friction and severe material change in shape. The obtained results show that at high aluminum and low copper, the yield strength and ultimate tensile strength reach their highest value, of 142 MPa and 188 MPa respectively.