Numerical study on solidification characteristics under pulsed magnetic field

The solidification characteristics under a pulsed magnetic field (PMF) are numerically investigated using a transient two-dimensional axisymmetric mathematical model that couples electromagnetic fields with fluid flow and solidification. The model is firstly validated and then applied to the solidification of Al-5 wt%Cu alloy under a typical PMF. Evolutions of the melt flow, temperature field and mushy zone as well as the solidification rate are studied. The results are compared with those obtained without a magnetic field and with a harmonic magnetic field (HMF) having the same peak current and a normal frequency of 50 Hz. It was shown that both the Lorentz force and Joule heat exhibit a phase difference for different locations in the melt, and their peaks are much greater than those induced by the HMF. The melt velocity is accompanied by a violent fluctuation whose amplitude is greater than that obtained with the HMF. The heat extraction of the melt is dominated by the forced convection during the liquid stage and early stage of solidification; thus, the mushy zone develops quickly. Nevertheless, the end time of solidification is a little longer than that without a magnetic field due to the presence of the Joule heat.