Pierre Desré

Chemical adsorption and temperature dependence of the solid-liquid interfacial tension of metallic binary alloys

Abstract In solid-liquid metallic binary systems, the variation of ρ = σ SL σ GB (ratio of solid-liquid interfacial tension to grain boundary tension of the solid solution) with temperature and composition of bulk phases, can be determined through the ‘dihedral angle’ method. We show that this information offers an experimental basis for evaluating interfacial adsorption: to do this, we present an analysis of ρ(T) curves which allows the signs of dσ SL dT and dσ GB dT be directly determined; and we establish a relation between the sign of dσ SL dT and that of the absolute adsorption at solid-liquid interfaces. Moreover, a method is proposed to evaluate the solid-liquid interfacial tension of pure metals by extrapolation of the ρ(T) data of the binary alloys.

Tensions superficielles d'alliages liquides binaires présentant un caractère dimmiscibilité: Al-Pb, Al-Bi, Al-Sn et Zn-Bi

Abstract Experimental measurements of surface tensions of Al-Pb, Al-Bi, Al-Sn, Zn-Pb and Zn-Bi alloys have been performed using two different methods (maximum bubble pressure and sessile drop).The experimental results are compared with those given in the literature. In addition, calculations of surface adsorption are made from Gibbs equation for Al-Pb and Zn-Bi alloys.

Surface tensions of binary liquid alloys with strong chemical interactions

Abstract The statistical approach developed uses the concept of “surrounded atoms”. The strong chemical interactions existing between the atoms of the liquid alloys studied are expressed, to a great extent, by the energy of stabilization of “privileged surrounded atoms” (PSA) of the mixture. The model permits to show the effects of these PSA on the surface properties (particularly surface tension) of three systems: AlCu, FeSi and NiSi.

Tension superficielle d'alliages liquides aluminium-cuivre

Resume Experimental measurements of the surface tensions of AlCu alloys have been made using two different methods (maximum bubble pressure and sessile drop). A compilation of specific weight data for the system is presented. The experimental results are compared with both those given in the literature and those calculated from a statistical thermodynamic model. Finally, calculations of the surface adsorption are made for T = 1100° C from the Gibbs equation and from the statistical model.

Introduction du concept thermodynamique d'énergie élastique partielle dans l'analyse de la ségregation superficielle d'alliages solides binaires

Abstract Previous models of surface segregation have generally been interpreted by means of a decrease in surface free energy. Nevertheless the reduction in lattice strain-energy which accompanies the transfer of misfitting solute atoms from the lattice to the surface, constitutes also a driving force for that phenomenon. By the introduction of the concept of the partial elastic energy, it is possible to present a theory which combines the two different aspects into a single formalism, valid in a crude approximation, for all concentrations.

Concentration profiles across solid-liquid interfaces of binary metallic systems

Abstract Coudurier, L., Eustathopoulos, N. and Desre, P., 1980. Concentration profiles across solid-liquid interfaces of binary metallic systems. Fluid Phase Equilibria, 4: 71–88. Concentration profiles across solid-liquid interfaces of binary systems have been calculated on the basis of a near-neighbour interaction model by using the statistics of Bragg-Williams. They are presented here for AlSn and NiPb alloys. These results related to the width of the interface, are discussed in terms of temperature, chemical interaction parameters and interfacial tension of the pure bodies. The calculated values of the interfacial tension, temperature dependence coefficient and chemical adsorption are compared with both experimental values and values obtained by a monolayer interface model.

Homogeneous nucleation via atomic density fluctuations in undercooled liquid metals

Abstract A new mechanism is proposed for homogeneous nucleation of crystalline phases via density fluctuations in undercooled melts. This process leads to the formation of crystalline nuclei of the critical size by a diffusionless transformation during relaxation of density fluctuations in the undercooled liquid. The proposed mechanism avoids the postulation of a distribution of energetically unfavourable sub-critical nuclei, as was required by earlier formulations.

Influence of the short-range chemical order effect on the partial interference functions of a dilute binary liquid alloy

Abstract An evaluation of the partial interference functions for a dilute binary liquid alloy in terms of the interference function of the solvent is presented. The calculation neglects size effects, but the influence of the short-range chemical order effect on the partial interference functions is studied. A quasichemical statistical treatment allows a calculation of the chemical effect to be made Results are presented for dilute alloys of Zn[sbnd]Al and Cu[sbnd]Sb and a direct comparison with experiment is made in the case of liquid Ag0.285 Li0.715.

CALCULATION OF THE PARTIAL STRUCTURE FACTORS IN BINARY LIQUID ALLOYS BY A THERMODYNAMICAL APPROACH

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. CALCULATION OF THE PARTIAL STRUCTURE FACTORS IN BINARY LIQUID ALLOYS BY A THERMODYNAMICAL APPROACH M. Favre-Bonte, J. Joud, P. Hicter, P. Desre