Effects of silicon content on the separation and purification of primary silicon from hypereutectic aluminum-silicon alloy by alternating electromagnetic directional solidification

摘要

Hypereutectic aluminum (Al)-silicon (Si) alloys with different Si contents were used to evaluate the effects of Si content on separation and purification by alternating electromagnetic directional solidification (AEM-DS) at 3 kHz. A relatively high pulling speed of 40 mu m/s was used for improved energy efficiency. After cooling, samples underwent AEM-DS, and efficient separation was obtained. The Si content in Si-rich areas exceeded 85 wt.% (considerably higher than the content in others) and exhibited not a slight relevance with the original Si contents in the hypereutectic Al-Si alloy. With regard to purification, impurities- particularly metallic impurities (Fe, Ti, and Ca)-can be removed to a low level. Electron probe microanalysis (EPMA) indicated that B content was lower in the Si-rich area than in the Al-Si alloy, suggesting that the segregation of B in solid primary Si was higher than that in Al-Si melt during AEM-DS. Moreover, the contents of metallic impurities (Fe, Ti, and Ca) and B decreased when the initial Si content in the Al-Si melt decreased. This finding was attributed to a lower silicon content, which indicated a lower melt temperature, thus allowing segregation at a lower temperature.