The Mechanism of P Removal by Solvent Refining in Al-Si-P System

To study P removal from Si by solvent refining in Al-Si-P system, series of quench experiments are carried out, which confirms a high P removal rate. An apparent segregation coefficient is introduced to characterize the segregation between primary Si and Al-Si melt, which are determined to be 0.00670, 0.0117, and 0.0201 when Si contents are 20, 30, and 40 wt pct, respectively, at the cooling rate of 0.556 mK s⁻¹. A calculation of Gibbs free energy of AlP in the alloys is also carried out and proves AlP precipitates before the primary Si formation. The formation of the AlP particles causes the decrease of P content in the Al-Si melt and contributes to the high P removal. Models to explain the P contents in the refined Si of each sample in this work are presented. These include three different cases to describe the interaction between the AlP particles and the primary Si.