多组元合金的凝固热力学原理-中国材料进展

文章信息/Info

Title:: Thermodynamic Principles for the Solidification of Multi Component Alloys

Author(s):: JIE Wanqi; （State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xian 710072, China)

摘要:: 以发展多元多相合金的凝固理论为目标，探讨了多组元合金自由能描述方法及其凝固过程的热力学平衡条件。多组元合金的自由能是由各组成元素的自由能、原子的组合排列引起熵的变化决定的理想混合自由能和由原子间交互作用引起的附加自由能三部分决定的。其中附加自由能的描述是难点，通常通过实验结果的拟合获得。固相的析出条件可通过自由能最低的热力学原理预测，而固相和液相成分的相关性则可通过化学位相等的热力学原理计算。在实际应用中，可以借鉴相图计算方法进行凝固过程的热力学分析，进而获得相图精细结构的数值计算结果。以AlMgSi合金为算例，进行了三元合金热力学平衡条件的分析。以该热力学平衡条件计算结果为基础，引入对固相和液相中扩散过程的分析，则可实现多组元合金凝固路径的预测。

Abstract:: As the fundamental principles for the solidification of multicomponent alloys, the thermodynamic equilibrium conditions between the melt and solid phases were discussed, based on description model of Gibbs free energy for different phases. The Gibbs free energy of a multicomponent alloy in a specialized phase is composed of three terms, i.e. the contributions of each pure elements, the energy introduced due to the ideal mixture of all elements, and extra energy caused by the chemical interaction among different elements. The last term is the most complicated one for description, which is normally fitted based on the experimental results. Solidification order of different phases can be predicated by comparing the Gibbs energy of different phases, and the solidification path can be evaluated by equilibrium of the chemical potentials of liquid and solid phases. As a practical method, Calphad method can be adopted for the numerical calculation in the equilibrium condition predications. The reliability of the method was proved by using the method for AlMgSi system. Combining the above thermodynamic method with diffusion analyses, the solidification path can be evaluated for any real solidification process.