Influence of tool positions variation on axial force, torque sensitivity, mechanical and microstructure properties of Al/Cu dissimilar FSW

Study on tool offset must be necessary to minimise IMCs formation and mechanical properties enhancement. Tool offset has a significant variations in the instantaneous force and torque are measures for the welding process. Increasing in the offset means more % of Al. This means softer IMCs formation and so increasing in offset distance decrease on load in the spindle/Z-axis and X-axis torque. A precise critical offset towards Al plate could result in a defect-free joint and superior mechanical performance. 1.5 mm offset gives smooth variations in the peaks, indicating a uniform distribution of the intermetallic compound, smooth weld surface and defect-free weld leads to better mechanical properties. In comparison to the Al base metal, the weld sample had more tensile and yield strength of 95% and 100%, respectively in case of optimised offset of 1.5 mm. 1.5 mm offset give maximum compressive strength (97.5% of the Al BM), maximum tensile properties and micro-hardness (176.2HV) due to fine grain with Al 44 μm and Cu 42 μm. As the grain size decreases so it helps to increase tensile properties and the strength of the joint depends on the offset distance and formation of the suitable amount of the intermetallics.