Electromagnetic pulse welded aluminium to copper sheet joints - morphological and mechanical characterization

This study investigated joining of Al to Cu sheets by electromagnetic pulse welding, which is a solid-state welding process that uses electromagnetic forces to join materials. The interfacial morphology and mechanical properties of the Al/Cu joints were analysed and related to the welding process parameters. The centre section of the Al/Cu joints evolved from a non-welded to a welded zone. The welded zone started with a wavy interface, consisting of thick interfacial layers with defects and evolved to a relatively flat interface without an interfacial layer. Interfacial phases resulted from solid-state mechanical mixing and/or very localised interfacial heating. The interfacial layers had a thickness ranging from 2-39 μm, an interface waviness amplitude up to 11 μm and contained 31-75 wt% Cu. The interfacial layer thickness and the weld length are determined by both the discharge energy and the stand-off distance. A trade-off existed between a homogeneous interface and the maximum weld length when the stand-off distance is changed. The interfacial layer exhibited an increased hardness compared to Al and Cu. A higher tensile force, up to 4,9 kN, was achieved at a higher energy and a lower stand-off distance. One of the factors determining the tensile force was the width of the welded area.