Effect of Cooling Rate on Boron Removal and Solidification Behavior of Al-Si Alloy

Abstract

The effect of cooling rate on boron removal and solidification behavior of Al-Si alloy with different silicon contents were studied during solar grade silicon purification. It is found that the boron removal rate is controlled by kinetic factor. A method is proposed to calculate apparent segregation coefficient of solidification process that spans over a temperature range. This apparent segregation coefficient is used to evaluate purification effect in alloy system with changing segregation coefficients. When average solidification temperature decreases, the apparent segregation coefficient of boron decreases. The average width and mass of primary silicon flakes decrease with increasing cooling rate. Impurity elements form intermetallic compound phases such as α-Al8SiFe2 and π-Al8Si6Mg3Fe in eutectic matrix.

Keywords

• solar grade silicon
• al-si alloy
• purification
• boron
• kinetics
• 81.10.fq