Thermodynamic assessment of the Bi-Mg binary system

Chunju NIU 1), Changrong LI 1)?, Zhenmin DU 1), Cuiping GUO 1) and Yongjuan JING 2) 1) School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China 2) Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024, China

摘 要：The Bi-Mg binary system had been assessed by adopting the ionic melt and the modified quasi-chemical models to describe the liquid phase with short range ordering behavior. In general considerations of the development of the thermodynamic database of the multi-component Mg-based alloys and the consistency of the thermodynamic models of the related phases, the Gibbs energy descriptions of all the phases in the Bi-Mg binary system were reasonably re-modeled and critically re-assessed in the present work. Especially for the liquid phase, the associate model was used with the constituent species Bi, Mg and Bi2Mg3. The Mg-rich terminal phase hcp_A3 was modeled as a substitutional solution following Redlich-Kister equation and the Bi-rich terminal phase Rhombohedral_A7 was treated as a pure Bi substance since the extremely small solubility of Mg in Bi. The low and high temperature non- stoichiometric compounds β-Bi2Mg3 and α-Bi2Mg3 were described by the sublattice models （Bi,Va）2Mg3 and （Bi）1（Bi,Va）3Mg6 respectively based on their structure features. A set of self-consistent thermodynamic parameters of the Bi-Mg system was obtained and the experimental thermodynamic and phase equilibrium data were well reproduced by the optimized thermodynamic data.

关键词：