Correlation of ultrasonic welding parameters with microstructural evolution and mechanical-electrical reliability of...

In the automotive industry, ultrasonic welding (USW) stands out as a highly effective solid-state welding technique. It is specifically designed for joining components within lithium-ion battery modules and energy storage systems. To achieve an optimal weight-to-body ratio, dissimilar materials like aluminum, copper, and nickel are joined to reduce the weight of electrical and electronic devices. This study presents a systematic analysis of aluminum (Al) and cupro-nickel (CuNi) dissimilar joints using USW, with variations in welding parameters. The lap shear strength results show that sonotrode pressure and welding energy have a greater impact on joint strength than the amplitude of vibration at all tested levels. Joint strength reached peak values of 942 N and 236 N, respectively, before declining sharply as weld energy increased due to the high interfacial temperature. Resistance measurements revealed that resistance decreased with increasing welding energy. Additionally, Al-CuNi specimens exhibited higher hardness values at the faying surface compared to their base metals. A metallographic analysis of the weld cross-section was conducted to evaluate diffusion across the joint interface, supported by X-ray energy-dispersive spectroscopy, electron backscatter diffraction, and X-ray diffraction to assess weld quality.