“…Dissimilar material welding via the FSW route needs extra care to obtain sound joints [ 5 , 63 , 166 , 167 , 168 , 169 , 170 ]; the reasons are the diversified properties across the joint line [ 168 , 169 , 171 ] such as melting point, thermal conductivity and coefficient of thermal expansion, flow stress and miscibility (solubility). In addition, the selection of tool material is the most important aspect along with its design, because the joining takes place due to the heat induced (~80%) by tool shoulder [ 102 , 103 , 107 , 108 , 109 , 110 , 111 , 161 , 162 , 163 ] and the tool pin governs the stirring action. In a study [ 120 ] on the effect of tool shoulder diameter, 18-mm shoulder-diameter with taper tool-pin geometry found suitable for producing quality joints of Cu/SS by FSW.…”