ANALYSIS OF THE CHEMICAL INTERACTIONS OF ASSOCIATES IN LIQUID METAL BINARY SOLUTIONS

The model of ideal associated solutions was used for the analysis of thermodynamic properties of liquid metal systems with negative deviations from Raoult’s law. However, absolute mass properties, rather than relative mass properties, were used for the chemical equilibrium determination according to the law of mass action. This allowed direct determination of the constants of equilibrium between solution associates and monomers and, thus, finding the value of free energy consumed for the formation of associates from monomers. With the assumption that such energy is identical to the energy of formation of the respective intermetallide from elementary substances, any adjustable parameters can be totally excluded from the model and reference thermodynamic information can be used from available data bases. The rule of associated solution phases was previously defined, which established that the number of associate types in each point of binary solution could not be greater than two. However, the number of known intermetallides for some alloys can exceed the indicated “limit” in several times. Consequently, it is necessary to find the criteria for identification of associates that stably present in solution. To study systems with a large number of associates in solution, reference information was used about intermetallides of ten A– B-type systems, in which one of the components was aluminum or copper. The assessment of possibility of spontaneous chemical reactions with the participation of associates has indicated that only А_рВ- and АВ-type associates can preserve in the solution area with predominant concentration of component A, and that only АВ- and АВ_q -type associates can preserve in the solution area with the predominant concentration of component B (р  and q are stoichiometric coefficients most often equal to two or three). Two stable “peripheral” associates А_рВ and АВq also interact with one another forming a small equilibrium area in the contact zone containing all three aforementioned associates. Stable associates can also be determined without analysis of running reactions if the associates with the least formation energy are considered to be stable. Therefore, А_рВ_q -type intermetallides with complex composition can be entirely omitted in the consideration of potential associates. The systems that have only one stable “peripheral” associate are characterized, as a rule, by sign-variable deviations from Raoult’s law in one of the solution components.

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