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.