Dissimilar Materials Joining between SSM 356-T6 and AA6061-T651 by Friction Stir Welding

Abstract

The aim of this research is to study the influence of welding parameters on the metallurgical and mechanical properties of friction stir welded butt joints of dissimilar aluminum alloy sheets between Semi-Solid Metal (SSM) 356-T6 and AA6061-T651 by Friction Stir Welding (FSW). The base materials of SSM 356-T6 and AA6061-T651 were located on the advancing side (AS) and on the retreating side (RS) respectively. The base materials were joined under different tool rotation speeds and welding speeds. The material flows from SSM 356 and AA6061-T651 were clearly visible in the weld nugget. In addition, the mixtures of fine equiaxed grain were observed in the stir zone. The increase in tool rotation speed results in the increase in tensile strength of the joints. As for welding speed associated with various tool rotation speeds, an increase in the welding speed affected lesser the base materials tensile strength up to an optimum value; after which its effect increased. Tensile elongation was generally greater at greater tool rotation speed. An averaged maximum tensile strength of 206.3 MPa was derived for a welded specimen produced at the tool rotation speed of 2,000 rpm associated with the welding speed of 80 mm/min. In the weld nugget, higher hardness was observed in the stir zone than in the thermo-mechanically affected zone. Away from the weld nugget, hardness levels increased back to the levels of the base materials.