Mechanism of B removal by solvent refining of silicon in Al-Si melt with Ti addition

Solvent refining of Al-Si-B alloy samples with different amounts of Ti additions are carried out, which confirms a high B removal rate with excessive Ti addition. An apparent segregation coefficient is introduced to characterize the segregation between primary Si and Al-Si melt, which are determined to be 0.0471 with 575 ppma Ti addition at the cooling rate of 50 mK·s−1. Temperature dependence of XTi(l)inAl-SimeltXB(l)inAl-Simelt2, individual Ti and B contents in the Al-29.3at.%Si melt from 1323 to 1123 K are calculated. It proves that TiB2 precipitates before the primary Si formation, which causes the decrease of B contents in the Al-Si melt and contributes to the high B removal rate. Moreover, BSE/SEM observation of TiB2 and (Al,Ti,Si) phase indicates a new competitive reaction mechanism in Al-Si-Ti-B system.