Variation of tool offsets and its influence on mechanical properties of dissimilar friction stir welding of aluminum alloy 6061 and S235JR mild steel by conventional belting milling machine

The tool offset parameter’s influence on joint strength of friction stir welding (FSW) of aluminum alloy 6061 and S235JR steel performed on a conventional belting milling machine was evaluated. The type of welding defects that arose at different tool offset values and how they affect the ultimate tensile strength (UTS) of the joints produced are also studied. It was found that at +0.2 and 0 mm offset, welding was incomplete and tunnel defects were formed, with average tensile strengths of 22.91 and 41.62 MPa for joints welded at each tool offset values respectively. Tool offset value of −0.2 mm was found to produce the best joints in terms of tensile strength, at an average of 95.73 MPa. For all joints, in terms of defects it was found that incomplete welding severely reduced tensile strength of joints, while tunnel defects also deteriorated tensile strength of joints albeit to a lesser degree.