Enhancing Segregation Behavior of Impurity by Electromagnetic Stirring in the Solidification Process of Al-30Si Alloy

Abstract

Increasing the removal efficiency of impurities during non-equilibrium solidification of hypereutectic Al-Si alloy remains a great challenge for the upgrading of metallurgical silicon (MG-Si) to solar grade Si (SOG-Si). Hence, a manageable method was provided to enhance the segregation behavior of impurities at the interface front of primary Si/Al-Si melt by introducing a rotating magnetic field (RMF) in the present work. Experimental results showed that electromagnetic stirring can improve the removal efficiency of impurities while achieving the separation of primary Si. The apparent segregation coefficients of the major impurities Fe, Ti, Ca, Cu, B and P were reduced to 7.5 × 10−4, 4.6 × 10−3, 7.9 × 10−3, 3.5 × 10−3, 0.1 and 0.16, respectively, under RMF of 25 mT and cooling rate of 2.5 °C/min. We confirmed that improving the transport driving force of impurities in the growth interface front of primary Si is an effective way to improve the segregation behavior of impurities, which would bring us one step closer to exploiting the economic potential of the Al-Si alloy solidification refining.