Effect of Si content on separation and purification of the primary Si phase from hypereutectic Al–Si alloy using rotating magnetic field

Abstract

Effect of Si content on separation and purification of the primary Si phase from hypereutectic Al–Si alloy using rotating magnetic field (RMF) was investigated in the present study. The results showed that the Si content has an obvious influence on the thickness of Si-rich layer formed around the sample and impurity contents in the purified Si. The thickness of Si-rich layer increases and the Si content in the Si-rich layer decreases with increasing Si content of the hypereutectic Al–Si alloy. The impurity contents of the purified Si can be reduced to a very low level. The typical metallic impurities (Fe, Ti, and Ca) have a high removal fraction. Electron probe microanalyzer (EPMA) analysis clearly reveals that the B content is lower in the primary Si phase than that in the Al–Si eutectic, suggesting the segregation of B element between the primary Si phase and the remaining liquid during solidification. In addition, the contents of B and metallic impurities (Fe, Ti and Ca) increase with increasing Si content of the Al–Si melt due to the segregation process starting at higher temperatures with higher Si content.