Strengthening Al-Cu ultrasonic spot welds using Ni interlayer for superior joint performance

Ultrasonic welding is a preferred method in the battery manufacturing industries due to its short weld duration and sustainable nature. Meanwhile, the utilization of dissimilar materials in battery tabs and interconnects presents a notable obstacle in achieving good metallurgical bonding. This study attempts to increase the strength of the joint by welding Al and Cu sheets with a Ni interlayer under various parametric conditions. The maximum tensile shear load and T-peel strength are achieved as 1158 N and 289 N at a weld pressure of 0.34 MPa and weld time of 0.39 s, respectively. The joint efficiency and strength reduction ratio are also calculated to demonstrate the quality of the weld. During this joining process, a peak temperature of 416°C is captured. Microhardness changes at the weld cross-section emonstrates the work hardening. Microscopic analyses reveal the influence of interlayer on the joint strength and its related metallurgical features.