基于Miedema模型三元合金Al-2%Si-xSc中Sc活度的计算

Calculation of Sc Activity in Ternary Alloy Al-2%Si-xSc Based on Miedema Mode

运用Miedema模型结合对称几何模型Kohler模型、非对称几何模型Toop模型计算了Al-2%Si-xSc(x=0.2%,0.4%,0.6%)三元合金中Sc的活度、活度系数及Sc与Si活度相互作用系数,在此基础上对Al-Si-Sc三元合金热力学性质进行分析,从而预测Sc在Al-Si合金中的热力学性质,计算结果表明:利用Miedema模型并结合对称几何模型Kohler模型、以及利用Miedema模型并结合非对称几何模型Toop模型可以计算出在熔体中Al-Si-Sc三元合金中Sc的活度以及活度系数.利用Toop模型计算得到Sc与Si活度相互作用系数和利用Kohler模型计算得到Sc与Si活度相互作用系数差别不明显,说明Kohler模型及Toop模型均适用于Al-Si-Sc三元合金,而且Sc与Si活度相互作用系数为正值,这样可以预估在熔体中Sc与Si之间存在排斥作用,不易形成二元化合物.

In this paper,the activity and activity coefficients of Sc in Al-2%Si-xSc(x=0.2%,0.4%,0.6%)ternary alloys and the interaction coefficients between Sc and Si are calculated by Miedema model,Kohler model and Toop model.Thermodynamic properties of Al-Si-Sc ternary alloys were analyzed to predict the thermodynamic properties of Sc in Al-Si alloys.The calculation results show that the activity and activity coefficient of Sc at 973 K in Al-Si-Sc melt can be calculated by using the Miedema model combined with the symmetric geometric model Kohler model and the asymmetric geometric model Toop model.The interaction coefficient between Sc and Si activity calculated by Toop model and the interaction coefficient between Sc and Si activity calculated by Kohler model are not obvious,indicating that both Kohler model and Toop model are applicable to Al-Si-Sc ternary alloy,and the interaction coefficient between Sc and Si activity is positive,which can predict the repulsion between Sc and Si in the melt,and it is difficult to form binary compounds.