Possibility of Complete Collecting Eutectic Si and Primary Si as Purified Si During Al-Si Solvent Refining with Zr Additions

The possibility of complete collecting eutectic Si and primary Si as purified Si during Al-Si solvent refining with Zr additions has been studied. From the ICP results, the B content in the eutectic Si is significantly higher than that in the primary Si with the low Zr addition (Zr addition ≤ 330 ppmw, Bmax=233 ppmw). With the excessive Zr addition, the B element in the melt is more and more distributed in the ZrB2 phase (over 95% with 3000 ppmw Zr addition), which causes the B content of primary Si and eutectic Si remained low level. Through the consistency of the estimated XZrB2 in this work with the theoretical value, the mechanism of the high-efficiency B removal is clearly revealed. The EDS analysis shows that the ZrSi2 phase is trapped and mixed in the collected Si crystal, which caused the Zr content in the Si crystal increasing abnormally, and the subsequent HCl + HF leaching process can effectively eliminate the trapped and mixed ZrSi2 phase in the Si phase. After leaching treatment, the B and Zr contents of eutectic Si and primary Si can reach the same level. This suggests that all Si crystals in Al-Si alloy can be used as purified Si, which greatly increases the recovery ratio of Si.