Effect of Alcohol on the Mechanical and Electrical Properties of Ultrasonic Spot Welded Cu/Cu Joints

In order to improve the Cu/Cu joint quality, the bottom Cu sheet surface to be welded was dampened by a drop of absolute ethyl alcohol before the welding. Then, the ultrasonic spot welding (USW) was utilized to join a 0.5 mm thick Cu sheet to a 1.0 mm thick Cu sheet. The results demonstrated that, due to the action of the alcohol, obvious changes of the welding interface temperature, effective thickness, bond density, interface microstructure, joint resistance, micro-hardness, lap shear strength and fracture mode occurred in comparison with the joint without alcohol. Discontinuous dynamic recrystallization took place at the welding interface and facilitated the migration of grain boundaries across the contact interface, leading to the formation of the metallurgical bonding between the two Cu sheets.