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Development of Thermodynamic Model on Phase Diagram Database

相图数据库热力学模型的开发

基本信息

批准号：
11694124
负责人：
ISHIDA Kiyohito
金额：
$ 4.1万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

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.

众所周知，有序化合物的磁性能如居里温度和平均磁矩与无序化合物的磁性能有不同的值。因此，磁性能的降低（增加）导致的化学有序与磁性能的相互作用降低（增强）了有序相的稳定性。在这个项目中，与瑞典皇家理工学院的Bo Sundman教授合作开发了一个考虑相互作用效应的新的热力学模型。考虑了磁有序反应和化学有序反应以及它们之间的相互作用，对b.c.c和f.c.c结构的相稳定性进行了模型计算。对Fe-X （X=A1， Ni和Co）体系的热力学评价也采用两个子晶格或四个子晶格s-CEF进行，包括相互作用效应。这些计算得出以下结论。(1) Fe-Al体系中难以理解的A2+B2相分离和三临界点是由于相互作用导致的化学和磁有序能的降低。(2) γ′-FeNi_3 （L1_2）和γ′-FeNi （L1_0）化合物的稳定性都被化学有序所产生的附加磁能所增强。计算的相图表明，γ′-FeNi （L1_0）相是稳定的。(3)在Fe-Co体系中，B2有序的稳定性主要来自于化学有序所带来的磁能增强。