Thermodynamic Database for Phase Diagrams of Mn-RE Binary Alloy Systems

Thermodynamic assessment of Mn-RE (RE: Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu) binary systems has been carried out by means of the calculation of phase diagrams method on the basis of experimental data including phase equilibria and thermodynamic properties. The Gibbs free energies of liquid phase and solid solution phases in the Mn-RE systems were all described by the subregular solution model with the Redlich–Kister formulation, whereas those of intermetallic compounds were described by the sublattice model. Sets of thermodynamic functions with self-consistent parameters leading to satisfactory agreement between calculated results and experimental data were eventually obtained. A primary thermodynamic database for the phase diagrams of the Mn-RE (RE: Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu) binary systems was developed from these essential thermodynamic parameters. This database can be used not only to calculate the phase equilibria and thermodynamic properties of binary Mn-RE systems but also to extrapolate to higher-order systems, which can provide theoretical guidance for design and development of high-performance Mn-RE alloy materials.     

Mo-RE二元合金相图的热力学数据库

利用CALPHAD方法,选择和建立合理的热力学模型,并结合相平衡及热力学性质的相关实验信息,对Mo-RE (RE: Ce, Pr, Nd, Sm, Eu, Tb, Ho, Er, Tm, Yb, Lu)各二元系相图进行了热力学优化与计算。其中,液相和端际固溶体相的Gibbs自由能采用亚正规溶体模型描述,气相的Gibbs自由能采用理想气体模型描述。计算结果与实验数据取得了良好的一致性,最终得到了一组自洽的合理描述Mo-RE二元系各相自由能的热力学参数,建立了Mo-RE (RE: Ce, Pr, Nd, Sm, Eu, Tb, Ho, Er, Tm, Yb, Lu)二元合金相图的热力学数据库。该热力学数据库可以提供相平衡及热力学性质等多种信息,为外推计算三元以及更多组元体系的相平衡提供理论基础,并为相关体系的合金设计及制备提供重要的理论指导。     

Isothermal Phase Diagrams of Binary Alloys and Two Oxidants

An example of an isothermal thermodynamic phase diagram of a quaternary system composed of a binary alloy and two oxidants has been calculated under appropriate values of the stability of the corresponding compounds, assuming that each metal forms only one compound with each oxidant. Initially, two-dimensional sections of the complete three-dimensional diagram made along planes corresponding to constant values of one of the variables involved were examined in detail. The actual structure of this type of three-dimensional diagram was then discussed by analyzing the shape and the boundaries of the various regions corresponding to the conditions of stability of each phase taken separately or in combination with other phases.     

贵金属二元合金相图研究的新进展和展望

对贵金属二元合金相图研究现状及其可靠性进行了全面的分析,把贵金属与周期表中各元素的相互作用分成连续固溶体、简单包晶型、简单共晶型、简单偏晶型、生成化合物的复杂体系和在固态和液态都不互溶的6种类型,并把它们放在元素周期表中进行研究后,定性总结了它们的若干规律;评价了二元相图坐标的热力学表示原理;评价了二元相图的半径验计算法和中间相的IUPAC（国际理论化学和应用化学联合会）和MSIT（国际材料科学组织）表示法,强调半经验的热力学计算法比较成熟,而按第一原理的理论计算法尚处在快速发展中;展望了贵金属二元合金相图的发展方向。     

Thermodynamic Phase Diagrams of Ternary Alloys Exposed to a Single Oxidant

Oxidation of Metals - A simple example of an isothermal thermodynamic phase diagram for a quaternary system composed of a ternary A–B–C alloy reacting with a single oxidant (O) has been...     

Thermodynamic Characteristic and Phase Evolution in Immiscible Cr–Mo Binary Alloys

This paper systematically reports the thermodynamic characteristic and phase evolution of immiscible Cr–Mo binary alloy during mechanical alloying(MA) process. The Cr–35Mo(in at%) powder mixture was milled at 243 and258 K, respectively, for different time. For comparative study, Cr–15Mo and Cr–62Mo powder mixtures were milled at 243 K for 18 h. Solid solution Cr(Mo) with body-centered cubic(bcc) crystal structure and amorphous Cr(Mo) alloy was obtained during MA process caused by high-energy ball milling. Based on the Miedema's model, the free-energy change for forming either a solid solution or an amorphous in Cr–Mo alloy system is positive but small at a temperature range between 200 and 300 K. The thermodynamical barrier for forming alloy in Cr–Mo system can be overcome when MA occurs at 243 K, and the supersaturated solid solution crystal nuclei with bcc structure form continually, and three supersaturated solid solutions of Cr–62Mo, Cr–35Mo and Cr–15Mo formed. Milling the Cr–35Mo powder mixture at 258 K, the solid solution Cr(Mo) forms firstly, and then the solid solution Cr(Mo) transforms into the amorphous Cr(Mo)alloy with a few of nanocrystallines when milling is prolonged. At higher milling temperature, it is favorable for the formation of the amorphous phase, as indicated by the thermodynamical calculation for immiscible Cr–Mo alloy system.     

Critical Evaluation and Thermodynamic Optimization of the Binary Systems in the Mg-Ce-Mn-Y System

Critical evaluation and thermodynamic optimization have been carried out for the Mg-Ce, Mg-Mn, Mg-Y, Ce-Mn, Ce-Y, and Mn-Y binary systems. All phase diagrams and thermodynamic data such as enthalpies of mixing, heats of formation, etc., were considered to obtain one set of model parameters of the Gibbs energies of all phases, which can reproduce the experimental data within experimental error limits. For the liquid alloys, the Modified Quasi-chemical Model in the pair approximation was used to treat short-range-ordering.     

High-Entropy Alloys with a Hexagonal Close-Packed Structure Designed by Equi-Atomic Alloy Strategy and Binary Phase Diagrams

High-entropy alloys (HEAs) with an atomic arrangement of a hexagonal close-packed (hcp) structure were found in YGdTbDyLu and GdTbDyTmLu alloys as a nearly single hcp phase. The equi-atomic alloy design for HEAs assisted by binary phase diagrams started with selecting constituent elements with the hcp structure at room temperature by permitting allotropic transformation at a high temperature. The binary phase diagrams comprising the elements thus selected were carefully examined for the characteristics of miscibility in both liquid and solid phases as well as in both solids due to allotropic transformation. The miscibility in interest was considerably narrow enough to prevent segregation from taking place during casting around the equi-atomic composition. The alloy design eventually gave candidates of quinary equi-atomic alloys comprising heavy lanthanides principally. The XRD analysis revealed that YGdTbDyLu and GdTbDyTmLu alloys thus designed are formed into the hcp structure in a nearly single phase. It was found that these YGdTbDyLu and GdTbDyTmLu HEAs with an hcp structure have delta parameter (δ) values of 1.4 and 1.6, respectively, and mixing enthalpy (ΔH _mix) = 0 kJ/mol for both alloys. These alloys were consistently plotted in zone S for disordered HEAs in a δ-ΔH _mix diagram reported by Zhang et al. (Adv Eng Mater 10:534, 2008). The value of valence electron concentration of the alloys was evaluated to be 3 as the first report for HEAs with an hcp structure. The finding of HEAs with the hcp structure is significant in that HEAs have been extended to covering all three simple metallic crystalline structures ultimately followed by the body- and face-centered cubic (bcc and fcc) phases and to all four simple solid solutions that contain the glassy phase from high-entropy bulk metallic glasses.     

Experimental Investigation and Thermodynamic Calculation of the Phase Equilibria in the Cu-Cr-W and Cu-Cr-Mo Systems

Phase equilibria of the Cu-Cr-W and Cu-Cr-Mo systems were experimentally determined by using metallography, X-ray diffraction (XRD) and electron probe micro-analyzer (EPMA) techniques. Based on the experimental data determined by the present work, the thermodynamic assessments of the Cu-Cr-W and Cu-Cr-Mo systems were carried out by using CALPHAD method. A consistent set of the thermodynamic parameters has been obtained, which leaded to a good fit between calculated results and the experimental data in both the Cu-Cr-W and Cu-Cr-Mo systems.     

Ag-Pd-Gd-20Ru和Ag-Pd-Gd-50Ru四元系部分相图研究

采用X -射线衍射、扫描电镜和显微金相分析等方法研究了Ag -Pd -Ru -Gd四元系相图的富Ag -Pd -Ru区域 (Gd <2 5at% )。测定了Ag -Pd -Gd - 2 0Ru和Ag -Pd -Gd- 5 0Ru四元系相图的 70 0℃部分等温截面。这两个等温截面上都分别含有 3个二相区 :Pd(Ag) + (Ru) ,(Ru) +Ag51 Gd1 4 ,(Ru) +Pd3Gd ;3个三相区 :Pd(Ag) +Pd3Gd + (Ru) ,Pd(Ag) +Ag51 Gd1 4 + (Ru) ,Pd3Gd +Ag51 Gd1 4 + (Ru) ;1个四相区 :Pd(Ag) +Pd3Gd +Ag51 Gd1 4+ (Ru)。这 2个截面上都不含有单相固溶区 ,也未发现新的四元中间相     

Stability evaluation of fluorite structure phases in ZrO2-MO2 (M=Th, U, Pu, Ce) systems by thermodynamic modelling

Thermodynamic modelling was demonstrated for ZrO₂-ThO₂ system based on the data for the ZrO₂-UO₂ and ZrO₂-CeO₂ systems in the literature. The calculated phase diagram for the ZrO₂-ThO₂ system showed a good agreement with the experimental data in the literature. Using the data obtained, together with the data for ZrO₂-UO₂, ZrO₂-PuO₂ and ZrO₂-CeO₂ systems, the stability of the fluorite structure phases in the ZrO₂-MO₂ (M=Th, U, Pu, Ce) systems was also studied with respect to the partial molar quantities. The effect of the ZrO₂ on the enthalpy in the MO₂ rich region increased as the cation size of the matrices decreased. The solubility limits of the ZrO₂ in the fluorite structure phase in this region also increased as the cation size of the matrix decreased. The effect of MO₂ on the partial molar Gibbs energy in the ZrO₂ rich region increased as the cation size of the MO₂ increased. It implies that the dissolution of the larger cation stabilises the fluorite structure of the ZrO₂ more.     

贵金属三元及多元合金相图研究的新进展

通过分析《贵金属合金相图数据库》中的资料,评述了目前世界上贵金属三元系合金相图的研究新进展,表明贵金属三元合金相图已成为贵金属合金相图研究的主要组成部分,三元系上的多元系合金相图的研究也取得了很大的进展,指出贵金属合金相图的研究与贵金属材料的研究与开发具有密切的关系。本文还介绍中国贵金属合金相图研究的情况。     

Thermodynamic Assessment of the Ru-Zr Binary System

The Ru-Zr system has been assessed by means of the Calphad approach. The solution phases (Liquid, (Ru), and were modeled with the sublattice formalism and the excess term of the Gibbs energy with the Redlich-Kister equation. The intermetallic compounds and RuZr, which have homogeneity ranges, were treated as the formula and by a two-sublattice model with a mutual substitution of Ru and Zr on both sublattices. The calculated phase diagram and the thermodynamic properties of the system are in satisfactory agreement with the experimental data.     

Thermodynamic Description of the Ce-Ga Binary System

The thermodynamic modelling of the Ce-Ga binary system was carried out with the help of the CALPHAD method. The liquid phase has been described with the association model with the Ce1Ga1 complex. The CeGa₂ over-stoichiometric intermetallic compound, which has a homogeneity range, was treated with the formula (Ce,Ga)_0.333(Ga)_0.667 by a two-sublattice model with Ce and Ga on the first sublattice and Ga on the second one while Ce₃Ga, Ce₃Ga₂, CeGa, and CeGa₆ have been treated as stoichiometric compounds. The calculated phase diagram and the thermodynamic properties of the system are in satisfactory agreement with the experimental data.