Influence of Ni Interlayer on Mechanical and Microstructural Properties in USW Processed Al–Cu Joints

In the realm of electromobility, ultrasonic welding has made great strides in recent years. The exceptional energy efficiency and solid-state joint creation provided by this joining method are remarkable. Joining of Al and Cu sheets for automotive battery packs is still challenging due to different physical properties and intermetallic phases resulting from dissimilar metal interactions. In this study, Al (AA1060) and Cu (UNS C11000) sheet are bonded with a Ni interlayer to improve the joint strength using several weld parameters. The experimental results of the tensile shear and T-peel tests show a noticeable improvement in weld strength. At 1170 J of weld energy, the utmost tensile shear and T-peel strengths are acquired as 1157 N and 288 N, respectively. In the temperature profile, it is evident that joint interface temperatures rise with increasing weld energy, reaching a maximum temperature of 398.6 °C at the bonding area. Microhardness testing also addressed the influence of plastic deformation and material softening developments on the weld interface. Both energy-dispersive X-ray spectroscopy and scanning electron microscopy are utilized to explore the effect of interlayer on the microstructural characterization of joints at weld interface.