Mechanical Behavior and Microstructure of Ultrasonic-Spot-Welded Al/Cu Dissimilar Joints with Zn Interlayer

The effect of Zn interlayer on the microstructural evolution and mechanical behavior of dissimilar ultrasonic-spot-welded Al/Cu joints was investigated. The tensile lap shear strength in relation to welding energy was analyzed. The experimental results show that two intermetallic compounds, Cu5Zn8 and Al2Cu, were generated at the interface of the ultrasonic-spot-welded Al/Cu joint with a Zn interlayer. The primary joining mechanisms of the joint included the intermetallic compound bonding and metallic bonding caused by solid shear plastic deformation. Meanwhile, with increasing welding energy, the plastic deformation of the material became more substantial. With increasing welding energy, the tensile lap shear strength of the joints first increased and then decreased for the ultrasonic-spot-welded Al/Cu joints with and without Zn interlayers. Under the energy input of 700 J, the bearing load capacity of the ultrasonic-spot-welded Al/Cu joints with a Zn interlayer improved significantly due to the observed intermetallic compound (Cu5Zn8).