日本金属学会誌

J. Japan Inst. Metals, Vol. 73, No. 9 (2009),
pp. 683-690

Thermodynamic Analysis on the Phase Separation of hcp Phase in the Mg-Y-Zn Ternary System

Ryuichi Masumoto, Hiroshi Ohtani and Mitsuhiro Hasebe

Department of Materials Science, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550

Abstract:

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.


(Received 2009/4/27)

Keywords:

phase diagram, thermodynamic analysis, calculation of phase diagrams (CALPHAD), first-principles calculations, long-period-stacking-orderd (LPSO) structures


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