Dissimilar metal joining of aluminum and copper plates using magnetic pulse welding and their joint strength

Abstract

Lap joining of aluminum and copper was performed using magnetic pulse welding. Two kinds of joining methods were examined. One method is joining using aluminum as the flyer plate (Al/Cu joining). The other method is joining using copper as the flyer plate (Cu/Al joining). The joining of aluminum and copper using the two methods at a charging energies from 0.5 kJ to 7.0 kJ was performed, and joint strength and interfacial microstructure were compared. The joint strength was evaluated by using tensile shear test. Interfacial microstructure was examined by using an optical microscope and a scanning electron microscope. Al/Cu joining succeeded at charging energy higher than 1.5 kJ. In contrast to that, Cu/Al joining was achieved at charging energy higher than 5.0 kJ. This different weldable charging energy range is considered to be due to density difference of aluminum and copper. In both joints, the fracture occurred at aluminum base metal by tensile shear test but the fracture strength of the Cu/Al joints was lower than that of Al/Cu joints. In case of Cu/Al joining, copper used as the flyer plate compressed aluminum as the parent plate, and obvious thickness decrease of aluminum was observed. The thickness decrease of aluminum is considered to result in the lower fracture strength of Cu/Al joints. Welding interface exhibited characteristic wavy morphology, which is similar to explosively welded interface. Intermediate layer was produced along the wavy interface. The wavy morphology and amount of intermediate layer of Cu/Al joints were smaller than that of Al/Cu joints.