（State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xian 710072, China)
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DOI:
10.7502/j.issn.1674-3962.2012.12.04
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Abstract:
As the fundamental principles for the solidification of multicomponent 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 multicomponent 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 AlMgSi system. Combining the above thermodynamic method with diffusion analyses, the solidification path can be evaluated for any real solidification process.