Optimizing electrical and mechanical properties via intermetallics distribution in Cu–Al spot welding

Abstract This study investigates the role of barrier layers in minimizing intermetallic formation during copper–aluminum spot welding to improve mechanical properties and electrical conductivity. Results show that introducing barrier layers, such as nickel and zinc, reduces hardness as expected but leads to complex effects on tensile strength and electrical conductivity. Two key mechanisms are identified: diffusion blocking, which limits intermetallics formation, and energy absorption modulation during welding, which influences strength based on barrier layer thickness. Nickel barriers significantly increase tensile strength, peaking at 15 μ m, while zinc barriers reach maximum effectiveness at 20 μ m. Beyond optimal thickness, incomplete welding penetration causes a decline in strength. Al2Cu is identified as the primary intermetallic compound formed during direct copper–aluminum welding. With nickel barriers, Al2Cu is dispersed, suggesting better diffusion control. Zinc barriers, on the other hand, lead to the formation of Al4Cu9 and Al2Cu, both dispersed similarly within the weld nucleus. Higher welding currents (1200 A) yield stronger welds than lower currents (1100 A), highlighting the importance of welding parameters in optimizing mechanical performance. Electrical resistivity is influenced by intermetallic layers and defects like cracks or voids at the interface, impacting overall electrical performance. This study provides insights into how barrier layers and welding conditions can be optimized to enhance the mechanical and electrical performance of copper–aluminum spot welds.