Evolution of Fe–rich phases in Mg melt and a novel method for separating Al and Fe from Al–Si–Fe alloys

Abstract

The recycling of high Fe–contained Al–Si alloys is a green industry and how to separate Al and Fe is the key point therein. An efficient technique using Mg melt to separate Al and Fe is proposed in this study. By introducing Al–14wt% Si–4wt% Fe alloy into Mg melt and adjusting melting, holding and cooling parameters, the evolution behavior and separation performance of Fe–rich intermetallics were investigated. A separation layer with Fe–rich particles was obtained at the bottom of the cooled ingot. A meta–stable phase Fe3Al0.7Si0.3 was detected, which only exists above 699°C confirmed by a thermodynamic calculation. Making β–Al5SiFe phase from the initial Al–14wt% Si–4wt% Fe alloy transform to Fe3Al0.7Si0.3 in Mg melt is beneficial to achieve higher separation efficiency since the Fe3Al0.7Si0.3 phase is Al–poor, indicating that quantities of Al are released to the Mg matrix. Holding at 750°C for 30min followed by a further holding at 650°C for 30min is regarded most proper in this study. This work may be referred by relative study on the evolution of intermetallics by introducing one matrix alloy into another melt.