Relationship between various enhancement strategies and the quality of joints made by ultrasonic metal welding: A review

Ultrasonic metal welding (USMW), a prominent solid-state joining technique, stands out by producing joints with high strength and minimal electrical resistance while consuming far less energy than traditional welding methods. This unique combination makes it particularly well-suited for precision welding of small components and thin metal sheets across various industries. At present, USMW attracts growing attention and adoption within the automotive industry, with a particular surge in applications for new energy vehicles. Its ability to reliably join delicate battery components, conductive materials, and lightweight structures aligns perfectly with the sector’s demands for efficiency, durability, and innovation. This paper attempts to summarize the effect of various enhancement strategies employed in UMSW on the mechanical performance of joints, including the process parameter optimization, the weldability between materials and their combinations, the methods of the thermal assistance and implanting interlayer materials between interfaces of the metal sheets. Furthermore, the related application of numerical simulation and online monitoring techniques were introduced, which provided a desirable platform for explaining the joint formation process and improving the welding process robustness. In addition, the mechanism of USMWed interface bonding evolution was discussed in detail. The research results synthesized in this review will provide valuable information for engineers developing USMW systems, researchers exploring related mechanisms, and future studies aiming to advance innovations in the USMW fields.