Ryuichi Masumoto, Hiroshi Ohtani and Mitsuhiro Hasebe
Department of Materials Science, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550
A thermodynamic analysis of the Mg-Y-Zn ternary system has been carried out, mainly focusing on the phase separation of the Mg-based hcp phase. The thermodynamic properties such as the formation enthalpy for the metastable hcp phase were estimated by using a first-principles method, because the solubility of Y and Zn was very limited in the stable phase diagrams. The calculations showed that, at least in the ground state, the solid solution of hcp had a strong tendency to phase separate between the Mg-rich side and the Y-Zn binary side. The characteristic long period stacking ordered (LPSO) structures observed in some Mg alloys might originate in this thermodynamic properties of the hcp solid solution.
phase diagram, thermodynamic analysis, calculation of phase diagrams (CALPHAD), first-principles calculations, long-period-stacking-orderd (LPSO) structures
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