Prediction and application of SiCa and SiCaFe alloy solutions by co-existence theory model

Based on the atom and molecule co-existence theory (AMCT), the activity models of SiCa and SiCaFe alloy solutions were established. The self-interaction coefficient and infinitely diluted activity coefficient of Ca, along with the interaction coefficient of CaFe in silicon alloy solutions, were calculated at a temperature range of 1723-1873K. The calculated data agree well with the experimental values and indicate that the atom and molecule co-existence theory is reliable for predicting the activity of SiCa and SiCaFe solutions. In addition, an iso-activity phase diagram of SiCaFe solution at 1723 K was plotted. The established activity model of SiCaFe shows that the activities of CaSi2 and FeSi2 in silicon solution are high. The activities of CaSi2 and FeSi2 are equal at xCa/xFe = 1.1. The activity of CaSi2 is 9.91 times greater than that of FeSi2 at xCa/xFe = 10. The effect of xCa/xFe on acid leaching was further discussed based on thermodynamics.