Influence of growth velocity on the separation of primary silicon in solidified Al-Si hypereutectic alloy driven by a pulsed electric current

Abstract

Investigating the separation of the primary silicon phase in Al-Si hypereutectic alloys is of high importance for the production of solar grade silicon. The present paper focuses on the effect of growth velocity on the electric current pulse (ECP)-induced separation of primary silicon in a directionally solidified Al-20.5 wt % Si hypereutectic alloy. Experimental results show that lower growth velocity promotes the enrichment tendency of primary silicon at the bottom region of the sample. The maximum measured area percentage of segregated primary silicon in the sample solidified at the growth velocity of 4 μm/s is as high as 82.6%, whereas the corresponding value is only 59% in the sample solidified at the growth velocity of 24 μm/s. This is attributed to the fact that the stronger forced flow is generated to promote the precipitation of primary silicon accompanied by a higher concentration of electric current in the mushy zone under the application of a slower growth velocity.