Reduction of Impurity Elements by Applying Electromagnetic Stirring in Fractional Crystallization

Aluminum smelting results in extremely high greenhouse gas emissions. Recycling of aluminum alloy is a key issue for decreasing the carbon footprint of aluminum products. To recycle aluminum scrap, impurity elements such as silicon, copper, etc., will become an obstacle. In this study, removing impurity elements from casting aluminum alloy which includes silicon higher than 7% was attempted by using a fractional crystallization method with electromagnetic stirring (EMS). EMS was implemented during cooling from the liquid phase to the solid-liquid coexistence temperature. Then the semi-solid aluminum slurry was obtained. After that by squeezing aluminum slurry, alpha-aluminum phase particles and the liquid phase were separated, and the number of alpha-phase particles was increased by applying EMS. The Si contains in alpha-phase was less than 2.0%. After squeezing, Si contains could be reduced from the original material.