Welding evolution and interfacial phenomena during ultrasonic spot welding of multi-layered aluminium alloy 1050 thin sheets

Abstract

Ultrasonic spot welding (USW) of multi-layered thin sheets is essential for lithium-ion battery and semiconductor package manufacturing. In this study, eight layers of aluminium alloy 1050 thin sheets were welded to an Al substrate employing USW, and the relationships among the strength, vibration histories, and microstructures were systematically examined. Interfacial strength increased with welding time, and fracture shifted from the interface to the base metal, progressing sequentially through the top, bottom, and middle-layers. In this sequence, the relative displacement at the interface was minimal and the number of recrystallised grains exhibiting shear texture increased. These results indicate that weld formation in multi-layer USW is caused by shear strain and does not occur simultaneously at all interfaces.