相图计算研究的进展

相图计算作为材料设计的一部分受到了人门更多的重视.本文概述了相图计算的优点,简要评述了相图计算方法的发展现状和前沿研究,着重强调了将第一性原理计算和相图计算方法相结合以及基于相图计算热力学数据库预测体系物理性质对于材料设计和冶金过程优化的重要性.     

LiF-NaF-KF体系的相图计算

基于CALPHAD技术首先评估了LiF-NaF和LiF-KF两个二元熔盐体系,液相和端际固溶体Halite相均采用Redlich-Kister多项式置换熔体模型描述,模型参数的优化选取实验相平衡数据和热化学数据以及本文根据第一性原理预测的数据.结合文献中已报道的NaF-KF体系的热力学参数,用Muggianu模型扩展至LiF-NaF-KF三元体系,根据三元共晶点的实验数据调整三元交互参数.最终的相图计算结果与绝大部分实验数据和第一原理计算数据吻合较好,由此获得了一套自洽且可靠的热力学参数,其能够准确描述LiF-NaF-KF体系的相平衡与热力学性质.      

LiBr-TbBr3体系相图热力学评估

采用CALPHAD技术热力学评估、计算了LiBr-TbBr3体系在整个成分范围内的平衡相图,其中组元LiBr和TbBr3的热力学性质分别采用SGTE热力学数据库和作者近期的评估结果,LiBr-TbBr3体系的热力学数据则通过对已有相图、热力学实验数据的精确评估优化获得.计算结果与实验数据的比较表明,本工作建立的热力学数据能够很好地解释现有实验结果、具有较好的物理意义.     

Bi-Te二元体系的热力学优化

在综合评估Bi-Te体系实验数据的基础上,结合第一性原理方法计算的各中间化合物的摩尔形成焓,采用CALPHAD方法优化和计算该二元合金体系的平衡相图。液相采用置换式溶体溶液模型,对于化学计量比中间化合物Bi_7Te_3、Bi_2Te_3以及具有较大固溶度的中间相Bi_2Te、BiTe,分别采用Neumann-Kopp规则以及双亚点阵模型描述其热力学函数。通过优化,得到一组合理自洽的热力学参数,并利用该热力学参数计算相图。计算的相图与文献报道的实验信息吻合较好,计算的863 K下液相Bi的活度以及混合焓也与已有的热化学数据符合良好。     

用特征晶体模型研究Au-Cu热力学性质

基于特征晶体模型，用最小二乘法拟合了Au-Cu热力学相互作用方程参数。在此基础上研究了Au-Cu合金的生成热、组元活度和Gibbs自由能随温度的变化曲线，确定了体系固液发生成分不变相变点的温度，计算结果与实验数据一致。评估了Au-Cu体系相图，其主要特征与CALPHAD评估结果和实验信息一致。     

集团变分法(CVM)的发展与应用

阐述了集团变分法(CVM)配置熵近似的特点.概括介绍了CVM在近年来的发展与应用,包括CVM与相图计算CALPHAD方法相结合描述多元系中的短程和长程有序;CVM的配置熵与第一性原理的形成焓计算相结合评估相平衡;CVM与路径概率方法相结合描述非平衡过程;以及连续位移-CVM处理具有晶格畸变或热振动体系的相稳定性.阐明CVM在计算材料学领域越来越重要的作用.     

相图计算及其应用

综述相图计算方法的发展现状、相图热力学计算常用的相描述模型及常用的热力学计算软件,并以Cu–Fe–Mn和Fe–Mn–Ni体系为例重点介绍相图热力学计算在材料设计及制备中的应用。     

MNO_3–Ca(NO_3)_2 (M=Li,Na,K)二元相图的热力学优化

基于CALPHAD方法对MNO3-Ca(NO3)2(M=Li,Na,K)二元相图的试验数据首次进行了热力学优化拟合,得到了3个二元相图的过量混合热力学性质的参数及Ca(NO3)2的熔化吉布斯自由能随温度变化的函数表达式,并用拟合的参数计算了3个二元相图,最后将计算得到的相图与试验相图进行了比较。     

Zr-Nb-O三元系的热力学优化

综合评估了文献报道的Zr-Nb-O三元系及其子二元系的相图及热力学信息。液相的Gibbs自由能采用离子亚晶格模型描述,固溶体相(α,β)和所有化合物(αZrO2,βZrO2,γZrO2,NbO,NbO2和Nb2O5)的Gibbs自由能都采用双亚晶格模型描述。用CALPHAD(CALculation ofPHAse Diagrams)技术,使用Pandat软件中的PanOptimizer优化模块,对Zr-O二元系进行了热力学优化,计算得到的相图和热力学性质与实验结果相吻合。应用优化的Zr-O二元系模型参数,结合Zr-Nb、Nb-O已有的热力学评估结果,对Zr-Nb-O三元系进行了热力学优化,得到了该体系的一套热力学模型参数。计算了Zr-Nb-O三元系在1273,1473和1773 K温度下的等温截面,与实验数据符合得较好。计算了若干该体系在富Zr区α+ββ的相转变温度,结果和实验测量也能较好地吻合。研究结果对建立多元锆合金热力学数据库,以及指导新型锆基合金材料的成分设计具有重要意义。     

作为材料设计基础的相图研究

介绍了现代材料设计与相图研究之间的关系，强调了计算相图的出现使相图研究成为材料的设计的一部分，相图计算程序系统的另一重要功能是评估和优化热力学参数，以双相纳米材料、宽滞后形状记忆合金、钕铁硼永磁合金、钛铝金属间化合物和低温用钢的研究开发为例，说明了相图研究在材料设计上的重要作用。     

Thermodynamic Assessment of DyCl3-MCl （M= Na, K, Rb, Cs） Systems

Using the CALPHAD （Calculation of Phase Diagram） technique, the DyCl3-MCl （M = Na, K, Rb, Cs） systems were optimized and calculated. The modified quasi-chemical model in the pair approximation for short-range ordering was used to describe the Gibbs energies of the liquid phase in these systems. From the measured phase diagram data and experimental thermodynamic properties, a series of thermodynamic functions were optimized base on an interactive computer-assisted analysis. The optimized parameters and the experimental data were thermodynamically self-consistent. The optimized results were discussed.     

Experimental Investigation and Thermodynamic Modeling for the Mg-Nd-Sr System

Microstructure examination, phase analysis, and DSC measurement on the equilibrated ternary alloys not only enabled exploration of the phase equilibria relations of the Mg-Nd-Sr ternary but also thermodynamic assessment of the ternary system in the context of the CALPHAD approach. Thermodynamic modeling, further coupled with first principle calculations, was thereafter used to predict a panoramic phase diagram for the Mg-Nd-Sr ternary system at the Mg-rich corner.     

Experimental Study and Thermodynamic Optimization of the FeO-V_2O_3 System

Optimization of the phase diagram of FeO-V2O3 system is a part of an on-going research project to develop a self-consistent multi-component thermodynamic database for vanadium slag from hot metal.Due to the lack of experimental data for optimization,a novel experimental investigation has been carried out by thermal analysis(DSC)with a series of slags on different V2O3 contents(i.e.3mass%-12mass%).All available thermodynamic and phase diagram data for the binary systems have been simultaneously optimized with CALPHAD(Calculation of Phase Diagrams)methods to give one set of model equations for the Gibbs free energy of the liquid slag as functions of composition and temperature.The modified quasi-chemical model was used to describe the binary slag system.It was demonstrated that the calculated phase diagram with the optimized parameters was in good agreement with the experimental data.     

Experimental Study and Thermodynamic Optimization of the FeO-V203 System

Optimization of the phase diagram of FeO-V20a system is a part of an on-going research project to develop a self-consistent multi-component thermodynamic database for vanadium slag from hot metal. Due to the lack o{ ex- perimental data for optimization, a novel experimental investigation has been carried out by thermal analysis （DSC） with a series of slags on different V2 03 contents （i. e. 3mass%- 12mass%）. All available thermodynamic and phase diagram data for the binary systems have been simultaneously optimized with CALPHAD （Calculation of Phase Dia- grams） methods to give one set of model equations for the Gibbs free energy of the liquid slag as functions of compo- sition and temperature. The modified quasi-chemical model was used to describe the binary slag system. It was dem- onstrated that the calculated phase diagram with the optimized parameters was in good agreement with the experi- mental data.     

Optimization and Calculation of TbCl3-ACl（A = Li, Na, K, Rb, Cs）Phase Diagrams

Thermodynamic information of the melts involvingrare earth halides and alkali halides plays an importantrole in the preparation of rare earth metals by moltensalt electrolysis and by metallothermic reduction. Theknowledge of thermodynamics of molten s…     

Thermodynamic assessment of the Cu-Ti-Zr system. I. Cu-Ti system

The CALPHAD method is used for the thermodynamic assessment of the Cu-Ti system that bounds the ternary Cu-Ti-Zr system, which is capable of forming amorphous alloys. The self-consistent parameters of thermodynamic models of the phases are obtained from data on the phase equilibria and thermodynamic properties of liquid alloys and intermetallic compounds. The Gibbs energy of the liquid phase is described using the associated ideal solution model. To describe the thermodynamic properties of the Cu₄Ti and CuTi intermetallic compounds with homogeneity range, sublattice models are used. The calculated phase diagram of the system and the thermodynamic properties of the phases are in good agreement with experimental data.