Separation and purification of Si from solidification of hypereutectic Al–Si melt under rotating magnetic field

Abstract

A low-cost and high-efficiency method to purify Si directly from cheap MG–Si at low temperature was proposed and demonstrated in this paper, which used power frequency rotating magnetic field (RMF) to separate the primary Si from a hypereutectic Al–Si alloy and was followed by the acid peeling. The separation mechanism was based on the flow characteristic of melt under RMF and the cooling condition of the liquid metal. A Si-rich layer with Si content of 65–59wt% was formed in the periphery of alloy, while the inner microstructure of the alloy was mainly the Al–Si eutectic structure. The refined silicon was collected after aqua regia leaching, and had much fewer typical impurities (Fe, Ti, Ca, B, P) than those in MG–Si, and the metallic impurities besides Al had removal fraction higher than 98%, which is mainly ascribed to the segregation effect of Al-30Si alloy during solidification under RMF.