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研究冶金级硅低速定向凝固过程中杂质铁的再分布。采用ICP-MS检测铁的浓度,绘制铁在固相、液相、晶界和晶体生长方向上的浓度示意图。铁浓度在固、液相中具有明显差异。依据质量守恒定理,计算得出溶质边界层约为4 mm,铁的有效分凝系数约为2.98×10~(-4)。在低速凝固条件下,铁容易偏析聚集在晶界。在生长方向上,由于低速凝固,铁浓度在硅锭86%高度以下几乎恒定,不完全符合Scheil方程规律。讨论了对流对铁再分布的影响,对流“死区”对铁再分布具有重要影响。
Study on Redistribution of Impurity Iron during Directional Solidification of Metallurgical Grade Silicon at Low Velocity. The concentration of iron was measured by ICP-MS and the concentration of iron in the solid phase, liquid phase, grain boundary and crystal growth direction was plotted. Iron concentration in the solid, liquid phase has significant differences. According to the mass conservation theorem, the solute boundary layer is calculated to be about 4 mm, and the effective segregation coefficient of iron is about 2.98 × 10 -4. Under low-speed solidification conditions, iron tends to segregate and aggregate at grain boundaries. In the growth direction, due to the low-speed solidification, the iron concentration is almost constant below 86% of the ingot, which does not fully comply with the Scheil equation. The effect of convection on the redistribution of iron is discussed. Convection “dead zone ” has an important influence on redistribution of iron.