Influence of Tool Shape on Friction Stir Welded Joint of Aluminum and Steel with Circular Weld Line

Abstract For the weight reduction of drive train in automotive, it is necessary to fabricate circular weld of die casting aluminum alloy and carbon steel with high welding efficiency. In this study, friction stir welding of ADC12 and S45C with circular weld line was evaluated, and the effect of welding tool shape was investigated for improving the weldability. The welding tool with flat shoulder was possible to fabricate the weld of ADC12 and S45C with a thin reaction layer with less than 1 μm. However, the mechanical strength of the weld was lower than that of ADC12. This is attributed to the microstructure of weld interface. Thus, material flow during FSW was enhanced by using a welding tool with a screw probe and a scroll shoulder. The fabricated weld by the welding tool achieved high weld strength equivalent to ADC12. In this weld, uniform and thin reaction layer about 50 nm was formed on the weld interface.