Simultaneously removal of P and B from Si by Sr and Zr co-addition during Al-Si low-temperature solvent refining

Abstract

To remove the key impurity elements, P and B, from primary Si simultaneously, Sr and Zr co-addition to Al-Si alloy systems during solvent refining has been investigated. Sr reacts with Al, Si, and P in the melt to form a P-containing Al₂Si₂Sr phase and Zr reacts with B to form a ZrB₂ phase. In the Al-Si—Sr—Zr system, high removal fractions of P and B in the primary Si, with 84.8%—98.4% and 90.7%—96.7%, respectively, are achieved at the same time, respectively. The best removal effect is obtained in the sample with the addition of Sr-32000+Zr-3000 µg·kg⁻¹, and the removal fractions of P and B in the purified Si reach 98.4% and 96.1%. Compared with the Sr/Zr single-addition, the removal effects of Sr and Zr co-addition on P and B do not show a significant downward trend, indicating that the nucleation and growth of the B/P-containing impurity phases are mutually independent. Finally, an evolution model is proposed to describe the nucleation and the growth stages of Sr/Zr-containing compound phases, which reveals the interaction between the impurity phases and the primary Si.

Keywords

Al₂Si₂Sr phase / zirconium boride phase phase / directional solidification / solvent refining

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