Inclusion Removal in Molten Magnesium by Pulsed Electric Current

Abstract

The effect of pulsed electric current on the removal of MgO inclusions, which deteriorate mechanical and corrosion properties of magnesium alloys, was investigated. Through characterizing the number and size distribution of MgO inclusions, it’s found that the MgO inclusions were expelled to the surface (bottom and top) of the magnesium alloy melt and then absorbed by the coating agent, treated by the electropulsing. Besides, the electropulsing also promoted the aggregation of the inclusions, but the large size inclusion only exists on the surface of the sample. Based on the differences in electrical properties between the inclusions and the magnesium alloy melt, a force from electric current to electrically neutral MgO inclusion has been identified to drive the particles’ movement. Further, the results of numerical calculation show that under the action of pulse current, the migration of inclusions to the surface can reduce the system free energy, and the aggregation tendency between two inclusions with a relatively large radius is significantly stronger than the two inclusions with a smaller radius. The excellent agreement between numerical calculations and experimental data demonstrates that employing the electropulsing to separate the particles from the liquids is a fantastic new method in metal melt purification.