Effect of welding velocity on macro/microstructure and mechanical properties of multiple-thin-foils Cu/Al joints fabricated by resistance rolling welding

In the present study, three layers of aluminum (Al) and a single layer of copper (Cu) were joined by resistance rolling welding (RRW) and the impact of welding velocity on microstructure, mechanical property and electrical property was investigated. The results showed that the welding velocity was identified as the most significant parameter. With decreasing the welding velocity from 11 mm/s to 1 mm/s, the mechanical property of the joints initially showed an increase, reaching a maximum coach-peel peak load of 185.25 N, due to the larger well bonded region, then decreased owing to the high-temperature softening of the base metal. The electrical resistance of the joint demonstrated a consistent varying, characterized by an initial decrease owing to the larger completely bonded region and then increased with the decreasing welding velocity due to the excessive generation of Al₂Cu with high electrical resistance. A cooling system was thus utilized to reduce the welding temperature to relieve the high-temperature softening, that successfully improved the welding quality of the joint by an 11.5% increase in the coach-peel peak load.