Effect of standoff distance on interfacial characteristics and mechanical properties of Al/Cu MPW joints

Abstract

In this work, Al6082-T6 to Copper were effectively joined by magnetic pulse welding (MPW). The interfacial characteristics and mechanical properties of joints were investigated at different standoff distances and constant input voltage by SEM, EDS, XRD analyses, microhardness and shear strength tests. SEM results showed that the various interface microstructures such as wakes, vortices, intermediate pocket/layer and porous structure were unveiled due to the diverse impact velocities. The XRD results from the fracture surface of the Cu side exhibited the formation of intermetallic compounds including Al₂Cu, AlCu and Al₄Cu₉ at standoff distances of 2.3, 3 and 4 mm which is caused by melting and subsequent accelerated element interdiffusion at the weld interface. Microhardness test results indicated the increased hardness of weld interface for all weld joints as a result of the work hardening of presence of the intermetallic compounds. Shear strength test results demonstrated that the highest shear forces are obtained as 12,300 and 13,500 N for weld made at standoff distances of 1.5 and 2.3 mm. These joints showed the failure of the base metal during shear test manifesting the adequate strength. Other weld samples had lower shear force and revealed failure of the weld zone owing to the presence of microcracks, pores, cavities and unbonded areas at the weld interface. Fractography analyses disclosed the appearance of large dimple area and small brittle area in fracture surface for standoff distance of 3 mm. Also, at standoff distance of 4 mm, splash droplets were observed in fracture surface suggesting the melting and evaporation of aluminum.