Melt flow and grain refinement in Al-Si alloys solidified under the influence of applied electric currents

The application of electric currents during solidification can cause grain refinement in metallic alloys. However, the knowledge about the mechanisms underlying the decrease in grain size remains fragmentary. This study considers the solidification of Al Si alloys under the influence of electric currents for the configuration of two parallel electrodes at the free surface. Solidification experiments were performed under the influence of both direct currents (DC) and rectangular electric current pulses (ECP). The interaction between the applied current and its own induced magnetic field causes a Lorentz force which produces an electro-vortex flow. Numerical simulations were conducted to calculate the Lorentz force, the Joule heating and the induced melt flow. The numerical predictions were confirmed by isothermal flow measurements in eutectic GaInSn. The results demonstrate that the grain refining effect observed in our experiments can be ascribed solely to the forced melt flow driven by the Lorentz force.