Simulation of electromagnetic-flow fields in Mg melt under pulsed magnetic field

The effects of a pulsed magnetic field on the solidified microstructure of pure Mg were investigated. The results show that microstructure of pure Mg is considerably refined via columnar-to-equiaxed growth under the pulsed magnetic field and the average grain size is refined to 260 μm under the optimal processing conditions. A mathematical model was built to describe the interaction of the electromagnetic-flow fields during solidification with ANSYS software. The pulsed electric circuit was first solved and then it is substituted into the magnetic field model. The fluid flow model was solved with the acquired electromagnetic force. The effects of pulse voltage frequency on the current wave and on the distribution of magnetic and flow fields were numerically studied. The pulsed magnetic field increases melt convection, which stirs and fractures the dendritic arms into pieces. These broken pieces are transported into the bulk liquid by the liquid flow and act as nuclei to enhance grain refinement. The Joule heat effect produced by the electric current also participates in the microstructural refinement.