Nanoparticle-enabled strengthening of aluminum and magnesium resistance spot welds

Abstract Joining of aluminum and magnesium alloys holds significant potential for the automotive industry focused on light-weighting. This paper evaluates the impact of nanoparticle inclusion and interlayer thickness on the properties of welded joints produced by Resistance Spot Welding (RSW). The interlayer was a Ni-coating, containing Al2O3 nanoparticles. Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectroscopy (EDS) assessed the weld microstructure, the diameter of the weld nugget, and the variation of composition across the weld nugget. The results indicated that both the diameter of the weld nugget and the penetration depth increased with increasing interlayer thickness. The most significant microstructural changes were observed at the fusion interfaces with the nanoparticle causing grain size reduction and dispersion strengthening. In cases where thick interlayers were used the weld nugget was comprised of large sections of un-melted coating and severe cracking. The results also show that the strength of the weld nugget increased with increasing interlayer thickness to a maximum value of 690 N at 10 µm. The microhardness values recorded across the weld zone confirmed the presence of intermetallic compounds.