Liquid Binary Alloys Research Articles

A Calphad-compatible method to calculate liquid/liquid interfacial energies in immiscible metallic systems

For the calculation of liquid/liquid interfacial energies in monotectic metallic alloys only simplified models are known, which suppose the validity of the regular solution model for the liquid solution. In the present paper a Calphad-compatible method is developed to calculate the liquid/liquid interfacial energies in binary, ternary and multicomponent liquid monotectic alloys. The method can be considered as the extension of the Butler equation to the liquid/liquid interfaces. The first order interfacial phase transition has been predicted at a certain critical temperature, which is about 18% of the bulk critical temperature. Below this critical temperature the compositions of the two sides of the liquid/liquid interface are different, while above this critical temperature the compositions at the two sides of the interface are identical. The latter case is valid for the majority of liquid metallic systems above their monotectic temperatures. The method has been validated against the experimentally measured liquid/liquid interfacial energies in the Ga–Pb and Al–Bi systems. The method is found to be very sensitive to the correctness of the Calphad-assessment of the partial excess Gibbs energies of the components in the liquid solution. The excess Gibbs energy function of the liquid Al–Bi solution was reassessed using our recent exponential temperature dependence of the interaction energies.

The effective oxygen pressure of liquid binary alloys

In previous works a theoretical analysis was developed for the interactions of a pure liquid metal and an oxidizing atmosphere in both an inert gas carrier and a vacuum. In particular, the effects of oxidation reactions taking place in the gas phase and the evaporation of the condensed oxides were considered. In both cases the presence of oxidation phenomena contributed to maintaining interface cleanness and then strongly affected the shape of the boundary separating the oxidation and de-oxidation regimes. In this work we present a more general physico-mathematical analysis, which is extended to liquid binary alloys and their oxides. The theoretical results obtained indicate that the behaviour of the alloy towards oxygen tends to be similar to that of the less oxidizable component: so the existence of a volatile oxide can often prevent surface oxidation even if the corresponding metal is present in low percentages.

Atomic transport properties of Ag xSn 1−x liquid binary alloys

Atomic transport properties, in particular the shear viscosity and diffusion constants for Ag x Sn 1− x less simple liquid binary alloys are theoretically studied from a statistical mechanical theory called the distribution function method. The essential ingredients of this theory are the interionic interaction and the pair distribution function for hard spheres. The interionic interaction are described from a local pseudopotential model and the effective hard sphere diameters are obtained from the thermodynamic perturbative method known as the linearized Weeks–Chandler–Andersen (LWCA). Results of calculations for shear viscosities agree well with the available experimental data.

Mixing properties of X–Pb, (X = Cd, In) liquid binary alloys

We study the mixing properties of Cd–Pb and In–Pb segregating alloy systems using the Quasi-chemical approximation model (QCAM) within the framework of Quasi-lattice theory (QLT). The energetics of mixing in liquid binary alloys has been analyzed through the study of the various thermodynamic quantities. Positive deviation from Raoultian behavior was observed in the mixing properties of the alloys calculated. Our results are in good agreement with reported experimental data and support a weak demixing tendency in both Cd–Pb and In–Pb liquid alloys.

Lowest-energy structures of 13-atom binary clusters: Do icosahedral clusters exist in binary liquid alloys?

Although the existence of 13-atom icosahedral clusters in one-component close-packed undercooled liquids was predicted more than half a century ago by Frank, the existence of such icosahedral clusters is less clear in liquid alloys. We study the lowest-energy structures of 13-atom AxB13−x Lennard–Jones binary clusters using the modified space-fixed genetic algorithm and the artificial Lennard–Jones potential designed by Kob and Andersen. Curiously, the lowest-energy structures are non-icosahedral for almost all compositions. The role played by the icosahedral cluster in a binary glass is questionable.

Thermodynamic Properties of Liquid Binary Transition-Metal Alloys in the Bretonnet-Silbert Model

In the present study, we apply the Bretonnet-Silbert local model pseudopotential, which takes into account the s-d hybridization in interacting between ion and s-electron to calculate the thermodynamic properties of binary transition-metal liquid alloys. The Wills-Harrison approach is used to take into account the d-electron terms in the free energy. We use the simplest variant of the variational method of the thermodynamic perturbation theory (with the hard-sphere reference system), the Vashishta-Singwi exchange-correlation function, and the Lorenz form of the density of d-electron states. The free energy of mixing, internal energy of mixing, and excess entropy of mixing are calculated for a Fe-Co liquid alloy at different compositions near the melting temperature. The agreement with the experimental data is quite satisfactory.

Bulk and dynamic properties in Al–Zn and Bi–In liquid alloys using a theoretical model

A formalism that connects thermodynamic and dynamic properties such as viscosity and diffusion coefficient has been used to calculate the concentration dependence of the free energy of mixing, concentration–concentration fluctuations in the long-wavelength limit and the concentration dependence of diffusion as well as viscosity in Al–Zn and Bi–In binary liquid alloys at various temperatures. Our calculations show that a reasonable degree of chemical order exists in Bi–In system, while Al–Zn liquid alloy was observed to exhibit a liquid miscibilty gap or phase separation over the concentration range. It can be concluded that size effect plays a more prominent role in the energetics of Bi–In than it plays in Al–Zn alloy. This fact is substantiated by predicted dynamic properties of both systems.

Influence of difference in the atomic volumes of the components on the mutual diffusion in liquid binary alloys

Expressions relating the partial diffusion coefficients, macroscopic flow velocity, and mutual diffusion coefficient are obtained. Unlike the known Darken relations, the relations obtained take into account the difference in the atomic volumes of the solution components. The influence of the volume factor is more pronounced when the component concentrations are significantly different.

Comparison of Different Theoretical Models to Experimental Data on Viscosity of Binary Liquid Alloys

Six different theoretical equations are compared in the present paper with experimental data, measured for 28 binary liquid metallic systems. General conclusions are drawn on the ability of the different theoretical models to describe the concentration and temperature dependence of the viscosity of liquid alloys. A new equation is derived, being able to predict the viscosity in multicomponents alloy even if the viscosities of the pure components are not known.

Preface

Abstract The 12th International Conference on High Temperature Materials Chemistry (HTMC-XII) took place at the Vienna University of Technology, Austria, 17-22 September 2006. Previous conferences were held in 2000 in Juelich (Germany), and in 2003 in Tokyo (Japan). The conference was sponsored by IUPAC and organized by the Department of Inorganic Chemistry/Materials Chemistry of the University of Vienna together with the Austrian Chemical Society (GÖCH) and the Department of Materials Chemistry of the Vienna University of Technology. The local organizing committee was chaired by Profs. Adolf Mikula and Herbert Ipser of the University of Vienna. Special patronage was granted by the Austrian Federal Minister for Education, Science and Culture and by the mayor of Vienna. More than 150 participants from 25 countries worldwide came to Vienna to present their research in the field of high temperature materials chemistry and to interact with each other in a lively scientific discussion. A considerable number of scientists, especially from Russia and some Eastern European countries, had the chance to come to this conference for the very first time, partly due to partial financial support by the local organizers, for example, by reduced or waived registration fees. It was also a pleasure to see many young scientists who made new contacts with each other and with their senior colleagues from all over the world. The program contained nine plenary lectures, corresponding to the main topics, but also included two special lectures on topics of more general interest, such as "Do universities prepare for industrial careers" (by Knuth Consemüller, chairman of the Austrian Council for Science and Technology Development), and "The arts: What use to materials science" (by Mark Miodownik). The plenary lectures, with the exception of the lecture by Dr. Consemüller, are published in this issue. In addition, there were 51 oral presentations and 100 posters that were on display for the entire week. For this conference, IUPAC sponsored three poster awards, and the winners received a two-year subscription of Chemistry International, a copy of the IUPAC "Gold Book" as well as a certificate signed by the IUPAC president. The winners, as selected by an international jury, were Dario Manara of Italy ("The uranium-oxygen phase diagram at high temperature: Recent advances"), Yuriy Plevachuk of Ukraine ("Density and electrical conductivity of liquid Al-Fe and Al-Ni binary alloys"), and Jiři Popovic of the Czech Republic ("Thermodynamic optimization of the Ni-Al-W system"). The social program included a reception in the City Hall of Vienna, sponsored by the mayor of Vienna, as well as a conference excursion to the easternmost Austrian province, Burgenland, with visits to the small town of Rust on the shore of Lake Neusiedl and a guided tour through the Esterhazy Palace in Eisenstadt, the capital of Burgenland. This was followed by a string quartet concert with music by the Austrian composers Joseph Haydn (who had lived and worked in this particular palace for many years) and Wolfgang Amadeus Mozart (whose 250th birthday was celebrated in 2006). The excursion ended with a conference banquet in the state rooms of the palace. Judging from the comments of the participants, HTMC-XII was a big success, and many of the scientists promised to come back to the next meeting, HTMC-XIII. Most probably this will be held in 2009 in California, USA, organized by Prof. Alexandra Navrotsky of the University of California at Davis. Adolf Mikula and Herbert Ipser Conference Editors

Application of the Dzugutov Scaling Law for Atomic Diffusion to Binary Liquid Alloys - A Hard-Sphere Description

Article Application of the Dzugutov Scaling Law for Atomic Diffusion to Binary Liquid Alloys - A Hard-Sphere Description was published on April 1, 2007 in the journal High Temperature Materials and Processes (volume 26, issue 2).

Energy of formation for [formula omitted] and [formula omitted] liquid binary alloys

We have investigated the free energy of formation for Ag x In 1 - x and Ag x Sn 1 - x liquid binary alloys at temperatures 1173 and 1250 K, respectively. A microscopic theory based on the first order perturbation has been applied. The interionic interaction and a reference liquid are the fundamental components of the theory. The interionic interaction is described by a local pseudopotential. A liquid of hard spheres (HS) of two different effective diametres and charges is used to describe the reference system. The results of the calculations for energy of formation agree very well with the available experimental data. Our calculations also reveal that a simple perturbative approach along with appropriate effective pair potentials can produce nearly quantitative results for the concerned alloys.

A QUASI-LATTICE THEORY FOR COMPOUND FORMING TERNARY LIQUID ALLOYS

A Quasi-lattice model of liquid binary mixtures has been used to establish a model for calculating some thermodynamic properties of compound forming ternary liquid alloys. The effect of varying Z on the concentration fluctuations was also investigated. Results obtained for limiting case of the model are presented and compared with that obtained by Bhatia and Singh for binary liquid alloys. A framework for calculating the Warren Cowley short range order for ternary liquid alloys as a function of Z is also formulated.

Structural properties of molten dilute aluminium–transition metal alloys

The short-range order in liquid binary Al-rich alloys (Al–Fe, Al–Ti) was studied by x-raydiffraction. The measurements were performed using a novel containerless technique whichcombines aerodynamic levitation with inductive heating. The average structure factors,S(Q),have been determined for various temperatures and compositions in the stable liquid state. FromS(Q), the pair correlationfunctions, g(r), have been calculated. The first interatomic distance is nearly temperature-independent,whereas the first-shell coordination number decreases with increasing temperature for allthe alloys investigated. For the Al–Fe alloys, room-temperature scanning electronmicroscropy (SEM) studies show the formation of a microstructure, namely the existence ofAl13Fe4 inclusions in the Al matrix.

Thermochemistry of binary alloys of lanthanum with 3d-transition metals

The enthalpy of mixing for liquid binary alloys of lanthanum with 3d-transition metals (Sc, Ti, V, Cr, and Fe) is determined by a calorimetric method within the field of compositions rich in lanthanum. Data for the partial enthalpy of mixing in the La-3d-metal system with infinite dilution demonstrates a complex relationship of a change in it in the series of 3d-metals connected with gradual filling of the 3d-zone due to alloy formation with lanthanum.

Bulk and surface properties of liquid Al–Mg, Au–Sn, and Mg–Tl compound forming alloys

We have used phenomenological models based on statistical mechanics to study the bulk and surface properties of Au–Sn, Al–Mg, and Mg–Tl binary liquid alloys. Our study reveals that the three alloys are weakly ordered systems with the most stable intermetallic complexes at temperatures of 823 K, 1073 K and 923 K been AuSn, Al 3Mg 2 and Mg 4Tl, respectively. An analysis of Warren–Cowley short-range order parameter indicates that the weakest intermetallic compound is Al–Mg while Au–Sn is observed to be more chemically ordered than Mg–Tl. Furthermore, our surface properties calculations shows that Mg-atom and Sn-atom segregate to the surface over the whole concentration range of Al–Mg and Au–Sn alloys, respectively. In Mg–Tl, there is a competing effect between Tl-atom being drawn into the bulk and at the same time Tl-atom wanting to segregate to the surface over the whole concentration range.

Density and molar volume of liquid Ni–Co binary alloys

In this work, the density of liquid Ni–Co binary alloys was measured with a modified sessile method (MSDM). It was found that the density of the liquid Ni–Co alloys decreases with increasing temperature and cobalt concentration in the alloys, and the molar volume of liquid Ni–Co binary alloys increases with the increase of temperature and cobalt concentration. The partial molar volume of cobalt in liquid Ni–Co binary alloy has been calculated approximately as [(6.78 − 4.82 × 10 −4 T) − (1.74 − 1.67 × 10 −3 T) × X Co] × 10 −6 m 3 mol −1. Compared with the ideal mixing, the molar volume of Ni–Co liquid binary alloys shows a negative deviation.

Electrical resistivity of NaSn compound forming liquid alloy using ab initio pseudopotentials

The electrical resistivity of the compound forming liquid alloy NaSn is studied as a function of concentration. Hard-sphere diameters of Na and Sn are obtained through the inter-ionic pair potentials evaluated using Troullier and Martins ab initio pseudopotential, which have been used to calculate partial structure factors S ( q ) . Considering the liquid alloy to be a ternary mixture, Ziman's formula for calculating the resistivity of binary liquid alloys, modified for complex formation, has been used. Form factors are calculated using ab initio pseudopotentials. The results suggest that the Ziman formalism, when used with ab initio pseudopotentials, is quite successful in explaining the electrical resistivity data of compound forming binary liquid alloys.

Surface tension and viscosity of Sn‐based binary liquid alloys

AbstractThe concentration‐dependent variation of the surface tension and viscosity of Sn–X (X = Ag, Bi, In and Zn) liquid alloys has been theoretically investigated. The grand partition function for the surface has been solved in the framework of quasi‐lattice approximations to obtain analytical expressions for the surface tension and surface composition of the different types of binary liquid alloys. For the computation of viscosity, an expression has been used that involves not only thermodynamic properties but also hard sphere diameter, masses and some microscopic functions. The hard sphere diameter of the constituent atoms in the binary systems has been calculated by minimizing the pair potential obtained from pseudopotential formalism. The theoretical investigation not only reproduces the experimental results but also predicts similar variations in surface tension and viscosity of these alloys with the increase of the Sn component. The viscosities and surface tension of Ag–Sn and Sn–Zn systems decrease with the addition of Sn atoms, showing a negative deviation from the additive rule of mixing. The extent of the deviation is large in Ag‐rich and Zn‐rich alloys. The Sn–In system exhibits a decrease in viscosity up to 20% Sn followed by linear values, while no appreciable change is observed in surface tension values. The surfaces of Ag–Sn and Sn–Zn are quite enriched with Sn atoms whereas the Sn–In system exhibits much less of a segregation of Sn. In contrast, both surface tension and viscosity of the Sn–Bi system increase with the increase of the Sn component. The surface composition of Sn–Bi is quite different from that of the other systems because of the segregation of Bi atoms. The difference of hard sphere diameters affects viscosity considerably. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electrical Resistivity of Na–K Binary Liquid Alloy UsingAb-Initio Pseudopotentials

The study of electrical resistivity of simple binary liquid alloy Na–Kis presented as a function of concentration. Hard sphere diameters ofsodium (Na) and potassium (K) are obtained through the inter ionic pairpotentials evaluated using Troullier and Martins ab-initiopseudopotentials, which have been used to calculate partial structurefactors S(q). The Ziman formula for calculating resistivity of binaryliquid alloys has been used. Form factors are calculated using ab-initiopseudopotentials. The results suggest that the first principle approachfor calculating pseudopotentials with in the frame work of Zimanformalism is quite successful in explaining the electrical resistivitydata of compound forming binary liquid alloys.