Computer Simulations of the Aluminium-Silicon Anomalous Eutectic Growth Based on Multiphase Field Method

Abstract

Aluminium–silicon anomalous eutectic growth has been studied numerically using a phase-field model developed to predict multiple phases. The Si phase grew very slowly in a melt of eutectic composition, but then grew substantially faster when in contact with the solidifying Al phase. The Al-liquid interface was irregular while the Si-liquid interface was flat as a consequence of the low interfacial energy between liquid and Al phases compared with that between liquid and Si. By developing a mathematical nucleation criterion, eutectic growth patterns were predicted and are in good agreement with experimental observations. Two mechanisms were shown to stop locally the growth of the Si phase during solidification. The first is competitive growth between the Al and Si phases, and arises when faster growing Al surrounds the tip of the solidifying Si. The second is due to nucleation and growth of Al ahead of the solidifying Si. It also has been shown that the melt is more likely to be trapped within the Si phase than in the Al phase.