Microstructure Evolution of the Pb–Al Alloy Solidified Under the Effect of Electric Current Pulses

Abstract

A theoretical model was built to describe the microstructure evolution during the solidification of a liquid–solid phase separation alloy under the effect of electric current pulses (ECPs). Solidification experiments were performed with Pb–0.15 wt pct Al alloy and the microstructure evolution was simulated. The simulation results are consistent with the experimental ones. They show that the Joule heating effect of ECPs can enhance the melt convection; the electromagnetic force induced by ECPs leads to a migration of minority phase particles (MPPs) from the surface to the center; the electromagnetic energy induced by ECPs can effectively promote the nucleation of MPPs, resulting in the refinement of MPPs. The peak current density $\left( {j_{{{\text{max}}}} } \right)$ of ECPs and the temperature drop of the melt in the nucleation region during one pulse cycle $\left( {\Delta T_{{F,{\text{Nuc}}}} = F^{ - 1} \cdot \left( {\partial T/\partial t} \right)_{{{\text{Nuc}}}} } \right)$ dominate the refinement extent of MPPs. When the peak current density is lower than a critical value, the size of MPPs is almost unchanged. While when the peak current density is higher, the size of MPPs decrease rapidly. For a fixed value of $j_{{{\text{max}}}}$, there is an optimal value of $\Delta T_{{F,{\text{Nuc}}}}$ to achieve the best refinement extent of MPPs.