Resistance spot welding of Al6061 lap joints with a polyvinyl alcohol-bonded graphene interlayer

Abstract

Abstract In order to increase the lap shear strength and weldability of aluminium alloy (Al6061), spot welding is done in lap configuration with an interlayer of graphene nano-platelets (GNPs). The GNPs are bonded using polyvinyl alcohol (PVA) and drop-casted on one of the mating surfaces of the lap joint before the resistance spot welding process. The experiment is carried out using different welding currents and time cycles at a constant load. It was found that the processing parameters and the presence of GNP interlayer play an important role in the performance of the lap joint. An increase of approximately 60% in the lap shear strength was observed with GNP interlayer at optimum processing conditions. Interfacial–microstructure characterisation was carried out across the fractured surface of the lap joint by using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). An increase in hardness, a change in nugget diameter and the mode of failure were observed in the presence of the GNP interlayer. A detailed analysis of the possible weld strengthening mechanisms is included in this article.