Stable and metastable phase equilibria in binary Mg-Gd system: A comprehensive understanding aided by CALPHAD modeling  

作　　者：Huaijia Si Yuxun Jiang Ying Tang Lijun Zhang 

机构地区：[1]State Key Laboratory of Powder Metallurgy,Central South University,Changsha 410083,China [2]School of Materials Science and Engineering,Hebei University of Technology,Tianjin 300130,China

出　　处：《Journal of Magnesium and Alloys》2019年第3期501-513,共13页镁合金学报（英文）

基　　金：The financial support from the National Key Research and Development Program of China(Grant no.2016YFB0301101);the Hunan Provincial Science and Technology Program of China(Grant no.2017RS3002)-Huxiang Youth Talent Plan;the Youth Talent Project of Innovation-driven Plan at Central South University(Grant no.2019XZ027);the Hebei Provincial Science and Technology Program of China(Grant no.BJ2018026)-Outstanding Young Talents Plan is acknowledged;Ying Tang acknowledges the financial support from the Yuanguang fellowship released by Hebei University of Technology.

摘　　要：In this paper,a comprehensive understanding of stable and metastable phase equilibria in binary Mg-Gd system was conducted with an aid of the CALculation of PHAse Diagram(CALPHAD)modeling.Firstly,thermodynamic descriptions of all the stable phases in the Mg-Gd system were re-assessed by considering all the experimental data in the literature.The discrepancy between the phase equilibria and thermochemical properties existing in the previous assessments was eliminated,and the better agreement with the experimental data was achieved in the present assessment.Secondly,the Gibbs energies for metastable β"-Mg3Gd and β"-Mg7Gd were constructed based on the first-principles and CALPHAD computed results as well as their correlation,and then incorporated into the CALPHAD descriptions.The model-predicted solvuses of(Mg)in equilibrium with the metastable β"-Mg7Gd and β'-Mg7Gd compounds showed very good agreement with the limited experimental data.Finally,the presently obtained thermodynamic descriptions of both stable and metastable phases in the binary Mg-Gd system were further validated by realizing the quantitative Scheil-Gulliver solidification simulations of 5 as-cast Mg-Gd alloys,and the successful prediction of the precipitation sequences in Mg-15Gd and Mg-12Gd alloys during the aging process.

关 键 词：Mg-Gd system Phase equilibria Metastable phase CALPHAD Precipitation sequence 

分 类 号：TG1[金属学及工艺—金属学]