Three-dimensional modeling of electromagnetic field and fluid flow during solidification of an aluminum alloy in a pulsed magnetic field

Three-dimensional finite element models were built to describe the distribution of electromagnetic fields and fluid fields under a low frequency low voltage time-dependent pulsed magnetic field. The simulation results showed that eddy current circling around the axis of the melt can be induced by pulsed magnetic field. Periodic positive-negative Lorentz force in the melt was induced from the interaction between the current and magnetic field. The effects generated by the pulsed magnetic field included vibration, fluid flow and Joule heat. The melt flowed in the form of a multi-circle and the fluid velocity was composed of a base component and a pulse component. The temperature in the melt was homogeneous because of the fluid flow. Melt temperatures were measured and compared with the simulated results during solidification process of aluminum alloy A356 (Al-Si alloy), which qualitatively confirmed the decrease of temperature gradient. Moreover, the effects of material resistivity and electromagnetic parameters of the pulsed magnetic field were investigated. Materials with smaller resistivity took larger electromagnetic force. The fluid flowed much faster under larger excitation current density and frequency. Finally, the grain refinement mechanisms under the pulsed magnetic field were analyzed.