Effect of Ti addition to Cu-Si alloy on the boron distribution in various phases

Highlights: • Redistribution of B was achieved by Si-Cu-Ti solvent refining. • Effect of Ti content on the segregation behavior of B was studied. • A removal efficiency of 85% of B in the solvent-refined Si was confirmed. • The thermodynamics of Ti in the Cu-Si-B melt was quantified. In this study, titanium was introduced to a Cu-Si alloy as an impurity getter to redistribute boron. A small amount of Ti was melted with Cu-Si alloy, followed by cooling of the alloy to precipitate purified Si crystals which were later separated through multi-step leaching. The effects of Ti content on the distribution of various elements in different phases and microstructure of the solidified alloy were investigated. It was found that Ti in Cu-Si alloy facilitates boron removal by several mechanisms including formation of TiB₂ and decreasing the segregation coefficient of B between Si and Cu-Si. Addition of Ti to a Cu-50 wt%Si alloy, compared to silicon metal, showed a significant increase in B removal. An increase in Ti in the range of 1–5% increased B removal, reaching ∼85% at 5% Ti addition. Ti in excess of that required to form TiB₂ reacts with Si to generate TiSi₂, which collects impurities such as P and Al.