Calculation of phase diagrams of the iron-copper and cobalt-copper systems

Synthesis of phase diagrams has been made on Fe-Cu and Co-Cu systems using thermodynamic parameters obtained by analysis of data on phase boundaries and thermodynamic properties. An anomaly in solubility of copper due to the magnetic transition was confirmed to occur in αFe as well as γCo. It was also detected that the solidus curves in both the systems exhibit remarkable retrograde solubility.     

Calculation of the Ti-C,W-C and Ti-W-C phase diagrams

The two binary W-C and Ti-C systems were analysed in thermodynamic terms by using a thermodynamic model which allows for the use of sublattices. Those carbides, which show some variation in their Me/C-ratios, such as the TiC-carbide were treated as solution phases using this model. As a result of this analysis the two binary W-C and Ti-C phase diagrams could be calculated. By combining these results with the analysis of the Ti-W system presented by Murray (1) a number of isothermal sections of the ternary Ti-W-C system were calculated. These are in close agreement with the experimental data according to Rudy et al (2).     

On the thermodynamic stability of intermetallic phases in the AA6111 aluminum alloy

An experimental investigation of both as-cast and heat-treated AA6111 alloys pointed to the quaternary phase Al₁₆(Fe,Mn)₄Si₃ as the dominant intermetallic phase. Weight fractions of this phase were determined by extracting it from the alloys via a selective dissolution of the FCC matrix in boiling phenol. The fractions found were significantly greater than those predicted by thermodynamic modeling. In an attempt to resolve the contradiction, it was assumed that the thermodynamic stability of the quaternary phase reported in literature had been underestimated. In order to refine its thermodynamic characteristics, conditions of phase equilibria in which Al₁₆(Fe,Mn)₄Si₃ participated were handled within the framework of the CALPHAD method.     

Calculation of phase equilibria for an alloy nanoparticle in contact with a solid nanowire

Phase equilibria in a system constituted of an alloy nanoparticle in contact with a solid nanowire have been modelled based on the minimization of a Gibbs free energy function. The Gibbs free energy consists of a bulk, surface and interface contribution. The bulk contribution is taken from CALPHAD thermodynamic databases and the surface properties from the literature. The effect of particle size and surface and interfacial properties on the liquidus line of the Au-Ge and In-Si systems has been studied. The results are compared to the bulk phase diagram and phase equilibria calculated for nano-systems with different geometries.     

The theorem of corresponding relation between neighboring phase regions and their boundaries in phase diagrams (I)

Several fundamental concepts in phase diagrams have been discussed. The theorem of corresponding relation between the number of different phases in the neighboring phase regions Φ and the dimension R₁ of their phase boundary in the phase diagrams is derived from the phase rule. The five corollaries of this theorem for isobaric phase diagrams are derived also. By applying this theorem and its corollaries, the following results can be obtained. Both the boundary rule and contact rule of phase regions in phase diagrams may be deduced. The ten empirical rules for constructing the complex ternary isobaric phase diagrams from phase diagram units may be put on a theoretical basis. The relation between neighboring phase regions and their boundary in phase diagrams of one-, two-, three- and four-components of all types and in the different horizontal and vertical sections of ternary phase diagrams may be explained without introducing any supplementary concept.     

Models for the determination of kinetic phase diagrams and kinetic phase separation domains

Several theoretical models for the determination of kinetic phase diagrams for solid solution growth from the liquid phase are presented and compared to each other. These models include a Monte Carlo simulation model, used as a reference model, a previously defined analytical model, based on linear non-equilibrium thermodynamics, and a new model, rooted in the kinetics at kink sites.All models have in common that the composition of the growing solid phase tends to the liquid phase composition for increasing undercooling, enhancing mixing even for systems with a strong tendency to phase separation. However, depending on the system parameters considerable quantitative differences can occur between the results from the model based on non-equilibrium thermodynamics and the MC model. Instead, the new model follows very well the trends of the MC simulations, both for well-mixing systems and for phase separating systems.For phase separating systems the analytical models predict kinetic phase separation domains, zones in the kinetic phase diagram yielding steady state growth of more than one solid phase with different compositions. According to MC simulations such domains in phase space correspond to domain formation in real space. Also in this case the new model is consistent with the MC results.     

Program for the calculation and construction of isothermal phase stability diagrams

For the calculation and graphic construction of isothermal phase stability diagrams a procedure is proposed and described. In the calculations, coordinates of invariant points are determined first. Then phase boundaries connecting either two invariant points or an invariant point and a boundary point of a diagram are constructed. The algorithm described is limited to systems formed by three chemical elements, where besides the ideal gaseous mixture only single condensed phases are considered. Partial pressures of two gaseous species are used as coordinates of a diagram.     

Solubility phase diagrams coupled to computer science (DPAO) part I: Theory of the sequential representation

This article describes a computerized method for processing of data of solubility in order to establish a phase diagram of order equal to or greater than four. The experimental and/or theoretical data are initially coded automatically with a binary number. An iterative algorithm uses these binary numbers to classify all the fields of variance according to the Gibbs' phase rule. A new mode of representation, so called “equential”, allows a reciprocal correspondence between the n-dimension space of the components and the 2-dimension space of a graph.     

基于FORTRAN的Ca-Fe-Si-O体系logf（O2）-loga（SiO2）相图的计算

以Ca-Fe-Si-O体系多相组合的logf（O₂）-loga（SiO₂）相图为例介绍了一种相图计算方法及Fortran95语言编程的实现过程。首先根据Gibbs相律确定了各个单变度和无变度组合,并根据化学成分图解配平化学反应方程式。然后,按照文献中的模型和参数计算各种矿物相和组分的Gibbs自由能,进而在给定的温度压力下计算各条反应平衡线的logf（O₂）和loga（SiO₂）值。然后再根据Schreinemakers规则判断相图中介稳的相关系,并从计算结果中去掉单变度反应线的介稳部分和介稳的无变度点。最后讨论了温度、压力对平衡的影响和新的矿物相加入时的计算方法和注意事项。     

PHASECALC: A code for the calculation of pseudobinary phase diagrams using no adjustable parameters

Pseudobinary phase diagrams are often used in the analysis of ternary semiconductor compounds of the form B_1−xA_xC where A, B and C are the pure elements and 0?x?1. The code PHASECALC is used for the calculation of pseudobinary phase diagrams. The code utilizes the Stringfellow method, and a modification of this method, to perform this calculation using no adjustable parameters. PHASECALC computes the temperature dependent solidus and liquidus lines as a function of mole fraction x. PHASECALC requires the following input data: enthalpy of fusion, melting temperature, and lattice constant for the pure binary compounds (AB and BC), electronegativity, molecular weight, density and energy of vaporization for the pure elements A and B.     

A modified electrolyte-Uniquac model for computing the activity coefficient and phase diagrams of electrolytes systems

A modified electrolyte-Uniquac model describing the behaviour of single and multicomponent electrolyte systems was developed. The thermodynamic properties of electrolyte solutions are considered to be the sum of two contributions: the long-range represented by Debye–Hückel contributions and the local-composition expression (modified Uniquac type) that have been applied to account for short-range contributions. The local mole fractions are calculated based on the assumptions proposed by Chen and coworkers. The model has been tested on 86 aqueous electrolyte solutions at 298.15 K and results have been compared with those obtained from the Pitzer and electrolyte-NRTL models. The modified electrolyte-Uniquac model led to the accurate calculation of individual activity coefficient of ion. This new model can also be used to predict the excess properties and the salt solubility in aqueous multielectrolyte solutions with the interaction parameters obtained from binary data.     

Calculation of the T-X phase diagram for a mixture of liquid crystals

In this study we calculate the T-X phase diagram for a mixture of liquid crystals. In this calculation we use a mean field theory. We fit our calculated phase line equations to the experimental data from the literature. There is a very good agreement between our calculated and the experimentally observed phase diagram.     

Prediction of the equilibrium,paraequilibrium and no-partition local equilibrium phase diagrams for multicomponent Fe-C base alloys

A method is described for the accurate prediction of Fe-C base multicomponent phasediagrams in the α-γ-cem range for both equilibrium and no-partitioning transformation states (paraequilibrium or no-partition local equilibrium) and applicable for total alloy contents (Mn + Si + Ni + Cr + Mo + Cu) less than 5 wt% and Si less than 1 wt%. The equilibrium predictions based on independent thermodynamic data collated by Uhrenius are in excellent agreement with Ae₃ temperatures given in the U.S.S. Atlas and published by Grange in Metal Progress. Calculations of the A₁ (eutectoid) temperatures indicate that Fe-C-Cr alloys transform in the equilibrium partition mode whereas Fe-C-Mn and Fe-C-Ni alloys tend to favour the paraequilibrium mode. This latter inference is in broad agreement with the pearlite partitioning experiments of Ridley and coworkers.     

电力直流分路绝缘监测技术研究--电力直流在线监测与控制技术研究之四

讨论了发电厂变电站直流分路绝缘监测的意义和现状，提出了利用微处理器配置漏电流进行分路绝缘监测的一种方法，介绍了这种方法的原理和用于绝缘监测的漏电流探测器的工作原理。介绍了基于这种监测方法的监控主机的硬件和软件设计方法。