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.     

Coupled phase diagrams and thermochemical data for transition metal binary systems — I

A data base covering the transition metals has been developed which permits coupling of thermochemical and phase diagram data and can readily be employed to compute ternary and higher order systems. The current paper which will be the first in a series of contributions, details the following ten binary systems: iron-titanium, iron-cobalt, iron-niobium, iron-molybdenum, iron-tungsten, chromium-cobalt, chromium-niobium, chromium-molybdenum and chromium-tungsten. Subsequent contributions will cover other binary members permitting calculation of a wide range of ternary systems.     

Coupled phase diagrams and thermochemical data for transition metal binary systems — II

A data base covering the transition metals has been developed which permits coupling of thermochemical and phase diagram data and can readily be employed to compute ternary and higher order systems. The current paper, which is part of a series, details the following twelve binary systems: nickel-titanium, nickel-cobalt, nickel-niobium, nickel-molybdenum, nickel-tungsten, titanium-cobalt, titanium-niobium, titanium-molybdenum, titanium-tungsten, cobalt-niobium, cobalt-molybdenum and cobalt-tungsten. This brings the total of such systems covered to twenty five. This paper together with the past and projected contributions will cover other sufficient binary members in order to permit calculation of a wide range of ternary systems.     

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.     

Calculated phase diagrams of Cu-W, Ag-W and Au-W binary systems

Phase diagrams for Cu-W, Au-W systems have been calculated based on available thermodynamic data. It was assumed that there is no mutual solid solubility in all the cases. Liquid phase equilibria were calculated on the basis of sub-regular solution model using Miedema's interaction parameters. Vapour phase boundaries have also been determined.     

Thermodynamic assessments of binary phase diagrams in organic and polymeric systems

The Sanchez–Lacombe (SL) model and the Flory–Huggins model were used for the calculation of binary phase diagrams in organic and polymer systems, respectively. The thermodynamic parameters of the liquid and gas phases in acetone–carbon disulfide (CS₂), butane–heptane, cyclohexane–aniline systems, and liquid phases in polystyrene–polybutadiene and polystyrene–bisphenol A poly-carbonate systems were optimized, based on the experimental data. The calculated results with various pressures are in good agreement with the experimental data. It is hoped that this method will be widely applied in the prediction of binary phase diagrams in organic and polymer systems.     

Coupled phase diagrams and thermochemical descriptions of the titanium-beryllium,zirconium-beryllium and hafnium-beryllium systems

A data base covering the transition metals has been developed which permits coupling of thermochemical and phase diagram data and can readily be employed to compute ternary and higher order systems. Previous papers in the series of CALPHAD publications have illustrated development of the base through utilization of experimental phase diagram and thermochemical data. The present work examines the usefulness of Miedema's computed heats of solution for liquid phases in considering the development of coupled data for three simple transition metalberyllium systems. The final results are then employed to recalculate the titanium-beryllium-zirconium-ternary system in order to define the composition with the greatest liquid stability. Such information can be of particular value in synthesis of metallic glasses.     

Coupled phase diagrams and thermochemical data for transition metal binary systems — V

A data base covering the transition metals has been developed which permits coupling of thermochemical and phase diagram data and can readily be employed to compute ternary and higher order systems. The current paper, which is part of a series, details the following ten binary systems: aluminum-titanium, chromium-aluminum, aluminum-manganese, iron-aluminum, cobalt-aluminum, aluminum-nickel, aluminum-copper, niobium-aluminum, molybdenum-aluminum and tungsten-aluminum, thus bringing the total of such systems covered to fifty seven. This paper together with past and projected contributions will cover other binary members in order to permit calculation of a sufficiently wide range of ternary systems.     

Predicate diagrams for the verification of real-time systems

This article discusses a new format of predicate diagrams for the verification of real-time systems. We consider systems that are defined as extended timed graphs, a format that combines timed automata and constructs for modelling data, possibly over infinite domains. Predicate diagrams are succinct and intuitive representations of Boolean abstractions. They also represent an interface between deductive tools used to establish the correctness of an abstraction, and model checking tools that can verify behavioral properties of finite-state models. The contribution of this article is to extend the format of predicate diagrams to timed systems. We establish a set of verification conditions that are sufficient to prove that a given predicate diagram is a correct abstraction of an extended timed graph; these verification conditions can often be discharged with SMT solvers such as CVC-lite. Additionally, we describe how this approach extends naturally to the verification of parameterized systems. The formalism is supported by a toolkit, and we demonstrate its use at the hand of Fischer’s real-time mutual-exclusion protocol.     

Coupled phase diagrams and thermochemical descriptions of the iron-beryllium,cobalt-beryllium,nickel-beryllium and copper-beryllium systems

A data base covering the transition metals has been developed which permits coupling of thermochemical and phase diagram data and can readily be employed to compute ternary and higher-order systems. Previous papers in the series of CALPHAD publications have illustrated development of the base through utilization of experimental phase diagram and thermochemical data. The present work examines the phase diagrams and thermochemical properties of the iron-beryllium, cobalt-beryllium, nickel-beryllium and copper-beryllium systems in order to evaluate the characteristics of the $\text{A2}\text{B2}$ (bcc/CsC1) ordering reactions and their dependence on composition.     

Data decision diagrams for Promela systems analysis

In this paper, we show how to verify computation tree logic (CTL) properties, using symbolic methods, on systems described in Promela. Symbolic representation is based on data decision diagrams (DDDs) which are n-valued Shared Decision Trees designed to represent dynamic systems with integer domain variables. We describe principal components used for the verification of Promela systems (DDD, representation of Promela programs with DDD, the transposition of the execution of Promela instructions into DDD). Then we compare and contrast our method with the model checker SPIN or classical binary decision diagram (BDD) techniques to highlight as to which system classes SPIN or our tool is more relevant.     

Thermodynamically consistent model of a multicomponent mixture with phase transitions

The paper considers a thermodynamically consistent model of compressible multicomponent mixtures with phase transitions. For the isothermal case, this enables one to obtain surfaces of phase equilibrium and other thermodynamic functions in analytic form. Use is made of simple model equations of state and the model Gibbs potential, which are known to adequately describe the phase behavior of solutions in some practically important range of parameters. Such a thermodynamically consistent model is convenient for the numerical simulation of the filtration of multicomponent solutions with phase transitions—in this way we achieve a significant reduction in the execution time and reliability of numerical computation, and also exclude some unphysical solutions.     

Requirements specification via activity diagrams for agent-based systems

Goal-oriented agent systems are increasingly popular for developing complex applications that operate in highly dynamic environments. As with any software these systems have to be designed starting with the specification of system requirements. In this paper, we extend a popular agent design methodology, Prometheus, and improve the understandability and maintainability of requirements by automatically generating UML activity diagrams from existing requirements models; namely scenarios and goal hierarchies. This approach aims to overcome some of the ambiguity present in the current requirements specification in Prometheus and provide more structure for representing variations. Even though our approach is grounded in Prometheus, it can be generalised to all the methodologies that support similar notions in specifying requirements (i.e. notions of goals and scenarios). We present our approach and an evaluation based on user experiments. The evaluation showed that the activity diagram based approach enhances people’s understanding of the requirements, makes it easier to modify requirements, and easier to check them against the detailed design of the agents for coverage.     

支持向量机算法在熔盐相图数据库智能化中的若干应用

支持向量机（SVM）方法可被用于熔盐系未知相图的计算机预报,将已知的二元卤化物系相图数据作为训练集,体系组成的离子半径和电负性作为特征量,用SVM方法可预报中间化合物的形成与否,熔化类型（同分熔化还是异分熔化）和估计中间化合物的熔点。本文报道了M2M′F4型的中间化合物的形成判据,M3M′Cl6型化合物的熔化类型的判据以及MM′X4型中间化合物熔点计算的回归方程式。用“留一法”检验所得的数学模型并将结果与传统的模式识别方法（Fisher法和KNN）进行了比较,结果表明：SVM的预报准确率比Fisher法和KNN法都高。因此,SVM方法有望成为计算机预报未知相图的有力工具。     

An interactive computer program for calculating ternary phase diagrams

A computer program is described which calculates ternary phase diagrams from the thermodynamic properties of the phases. Sample calculations are given for the molten salt system KClCaCl₂NaCI, the alloy system 7nSnBi, the super-alloy system CrNlFe, and the organic system acetone-chloroform-methyl isobutyl ketone. A computational strategy known as the base phase method is used. This results in a simplification of the algorithms and a large Increase in efficiency. The program, which is highly Interactive with very flexible input and graphical output, is available on-line to North American and European users.     

Ortho-equilibrium and para-equilibrium phase diagrams for interstitial / substitutional iron alloys

A mathematical model for the evaluation of compositionally constrained thermodynamic equilibrium has recently been implemented into the computer program MatCalc. This model is applied to the calculation of para-equilibrium phase diagrams for some ternary model iron alloy systems Fe---X---C, with X = Mn, Ni, Cr and Mo. The results are compared to the corresponding full equilibrium (ortho-equilibrium) phase diagrams and the impact of each element on the austenite / ferrite / carbide transformation in steels is analyzed. The para-equilibrium phase diagrams are considerably more simple than the potentially complex ortho-equilibrium phase diagrams, showing cementite formation as the only stable carbide under para-equilibrium conditions. The driving forces for precipitation of cementite and the complex chromium carbides in the Fe---Cr---C system are evaluated as a function of the precipitate composition. The evaluation of the driving forces under para-equilibrium conditions predicts carbide precipitation behavior that agrees with experimental findings.     

Undulate phase boundaries on binary diagrams

Usually, an inflection point on a phase boundary is considered as an unambiguous indication that one of phases participating in the equilibrium is internally unstable, i.e. that it is prone to separation. Subsequently, it is habitually deemed that the inflection point may appear only if a thermodynamic model of this phase contains an excess term.

It is shown that in contrast to this belief, inflection points on a phase boundary may appear when a pure solid component or a stoichiometric binary phase is in equilibrium with the ideal binary solution, which is internally stable, indeed.