The Electrical and Mechanical Aspects of Aluminum and Copper Resistance Spot Weld Joints

Resistance spot welding (RSW) is widely used in the automotive industry, particularly for copper-aluminum alloys in electric cars. RSW joint conductivity is crucial for electric vehicles. Welded parts may fracture due to tension, altering conductivity. The study examines resistance spot post-weld joint metallurgy and deformation-induced conductivity changes. The electric resistance of similar and dissimilar RSW joints was examined during tensile tests. Metallurgical tests for RSW joints revealed an increase in grain size from the base metal (BM) to the heat-affected zone (HAZ) and finally the fusion zone (FZ). Satisfactory shear tension strength results were obtained for dissimilar joints (Al-Cu) at 690 N and similar joints (Al-Al) at 780 N, exceeding the minimum limit of 643 N. However, weld strength in similar joints (Cu-Cu) only achieved 933 N, less than the required strength of 1528 N. Furthermore, the relationship between deformation rate (i.e., applied stress) and electrical resistance has been shown. It was found that resistivity increases with increasing deformation stress, resulting in decreased electrical conductivity with a high percentage, representing 99.8, 99.66, and 99.49% for Al-Cu, Al-Al, and Cu-Cu RSW joints, respectively. The electrical resistance was measured at the maximum force of 650 N and maximum stress of 33.1 MPa. The results show (15.7 Ώ, 5.9 Ώ, and 1.99 Ώ) and the electrical conductivities (0.063 IS, 0.169 IS, and 0.502 IS) for the joints (Al-Cu), (Al-Al), and (Cu-Cu), respectively.