Simulation of Coupled Electric-magnetic-flow Fields and Microstructural Refinement of Pure Mg during Solidification under Pulsed Magnetic Field

摘要

This paper investigates the effects of a pulsed magnetic field on the solidified microstructure of pure Mg. The results show that microstructure is remarkably refined via columnar-to-equiaxed growth by the pulsed magnetic field and the average grain size is refined to 260μm at the optimal processing parameters. A mathematical model is built to describe the interaction of the electric-magnetic-flow fields during solidification by means of ANSYS software. The pulsed electric circuit is solved first and then it is substituted into the magnetic field model. The fluid flow model is solved with the acquired electromagnetic force in the magnetic field model. The effects of pulse voltage and frequency on the current wave and distribution of magnetic and flow fields are 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.