Development of Thermodynamic Model on Phase Diagram Database

众所周知，有序化合物的居里温度和平均磁矩等磁性性质与无序溶液的不同。结果，由于磁性的降低(增加)引起的化学有序和磁性有序之间的相互作用，有序相的稳定性被抑制(增强)。在这个项目中，通过与PROF的合作，建立了一个新的考虑相互作用影响的热力学模型。瑞典皇家理工学院的Bo Sundman。描述BC.C.相稳定性的模型计算。和FCC。结构的执行考虑了磁性和化学有序反应，以及它们之间的相互作用。用两个或四个亚晶格S-CEF对Fe-X(X=Al，Ni和Co)体系进行了热力学计算，考虑了相互作用的影响。这些计算结果表明：(1)Fe-Al系中难以理解的A2+B2相分离和三临界点源于相互作用引起的化学有序能和磁有序能的降低.(2)γ‘-FeNi_3(L1_2)和γ“-FeNi(L10_0)化合物的稳定性都因化学有序产生的额外磁能而大大提高.计算的相图表明γ“-FeNi(L10_0)相是稳定的。(3)在Fe-Co系统中，B2有序的稳定性主要是由于化学有序增强了磁能。

It is well known that magnetic properties such as the Curie temperature and the mean magnetic moment of ordered compounds have different values from those of disordered solutions. In consequence, the stability of the ordered phase is depressed (enhanced) due to the interaction between the chemical and magnetic ordering caused by the decrease (increase) of magnetic properties. In this project, a new thermodynamic model taking into account the interaction effect was developed by the collaboration with prof. Bo Sundman in the Royal Institute of Technology, Sweden. Model calculations to describe the phase stability of the b.c.c. and f.c.c. structures were performed taking into account the magnetic and the chemical ordering reactions and also the mutual interaction between them. Thermodynamic assessments of the Fe-X (X=A1, Ni and Co) systems were also carried out using two- or four-sublattice s-CEF, including the interaction effect. These calculations lead to the following conclusions.(1) The incomprehensible A2+B2 phase separation and tricritical point in the Fe-Al system originate in the depressed chemical and magnetic ordering energies caused by the mutual interaction.(2) The stability of both γ'-FeNi_3 (L1_2) and γ"-FeNi (L1_0) compounds is strongly enhanced by the additional magnetic energy due to the chemical ordering. The calculated phase diagram suggests that the γ"-FeNi (L1_0) phase is stable.(3) In the Fe-Co system, the stability of the B2 ordering arises mostly from the enhanced magnetic energy due to the chemical ordering.