Ultrasonic spot welding for high-quality joint formation in multi-material for automotive applications

Efforts to reduce the structural weight of autobody structures, enhance fuel efficiency, and reduce gas emissions have greatly increased the applications of lightweight multi-materials. Lightweight materials such as cast aluminum/magnesium (Al/Mg) alloys, 7xxx aluminum (Al) alloys, and advanced/ultra-high-strength steels are in high demand to replace mild steel for part consolidation, weight savings, recyclability, and enhanced crash resistance. However, joining these dissimilar materials, such as cast or recycled Al/Mg alloys to other materials, is challenging due to their high susceptibility to solidification cracking and porosity with conventional welding processes.

Ultrasonic spot welding (USW) leverages ultrasonic vibrations to produce frictional heat at lower temperatures at the interface for strong metallurgical bonding. USW has a softening effect due to ultrasound, which mitigates cracking caused by low ductility. Additionally, this technique provides great energy efficiency, productivity, and crack-free joints. This study focuses on the development of the USW process through in-process parameters. By optimizing these parameters, we aim to improve the reliability and performance of the welded joints, contributing to the advancement of lightweight multi-material architectures in automotive structures.