Effects of graphene nanoplates on microstructures and mechanical properties of NSA-TIG welded AZ31 magnesium alloy joints

The effects of graphene nanoplates (GNPs) on the microstructures and mechanical properties of nanoparticles strengthening activating tungsten inert gas arc welding (NSA-TIG) welded AZ31 magnesium alloy joints were investigated. It was found that compared with those of activating TIG (A-TIG), and obvious refinement of α-Mg grains was achieved and the finest α-Mg grains of fusion zone of NSA-TIG joints were obtained in the welded joints with TiO2+GNPs flux coating. In addition, the penetrations of joints coated by TiO2+GNPs flux were similar to those coated by the TiO2+SiCp flux. However, the welded joints with TiO2+GNPs flux coating showed better mechanical properties (i.e., ultimate tensile strength and microhardness) than those with TiO2+SiCp flux coating. Moreover, the generation of necking only occurred in the welded joints with TiO2+GNPs flux.