Influencing mechanism of an external magnetic field on fluid flow, heat transfer and microstructure in aluminum resistance spot welding

The magnetically assisted resistance spot welding (MA-RSW) method provides a promising approach for improving weld performance. However, the MA-RSW process involves complex multiphysics fields that make numerical modeling very challenging. Thus, most (RSW) models adopt electrothermal-mechanical coupling and ignore influence of fluid flows caused by electromagnetic forces on nugget growth. In this paper, magnetohydrodynamic (MHD) model, which couples electric, thermal, magnetic flow fields, is developed to explore influencing mechanism an external field (EMF) patterns microstructures aluminum welds. Numerical results show application EMF can lead formation Lorentz force in liquid nugget, transforms pattern from in-plane combined out-of-plane flow. velocity molten metal 5 times higher than RSW process, maximum temperature model reduced 774°C MHD 725°C. Therefore, joint exhibits 25.5% larger diameter, more 20% finer grain structure, fewer defects experimental results.