MICROSTRUCTURES SIMULATION OF MAGNESIUM-BASED ALLOYS DURING SOLIDIFICATION BY PHASE-FIELD METHOD

An expression is proposed for the anisotropic function of crystal-melt interfacial free energy for hexagonal metals, based on the combination of experiments and crystal structure. The phase field model of alloys, whose density free energy is built on the basis of thermodynamic extended substitutional-regular-solution approximation, incorporated into anisotropic function reflecting hexagonal symmetry, is established. Numerical computations of primary hcp-Mg phase dendritic growth in the freezing process of magnesium-based alloys melts are implemented. The three-dimensional dendritic morphologies of magnesium alloys microstructures, whose hierarchical branches can be seen clearly, are obtained, which have been well in agreement with experimental results and are obviously different from that of would be usually expected.