The vapour composition and the thermodynamic properties of Ni-Zr alloys in the liquid and solid states were studied by Knudsen-cell mass spectrometry over wide ranges of temperature (971-1896 K) and composition (0-99.8 mol% Zr). The accessible temperature range was enhanced by chemically generating volatile substances directly in the cell. For this purpose, the samples were mixed with powdered fluorides of magnesium, calcium, or sodium. Reduction reactions occurring in the cell produced zirconium fluorides, which were examined with the mass spectrometer. The thermodynamic functions of formation of all crystalline phases in the Ni-Zr system were determined. A representative file of experimental data was obtained for the Ni-Zr melt. It comprises about 900 values of the activities of both components at various concentrations and temperatures. The concentration and temperature dependences of the thermodynamic functions of liquid Ni-Zr alloy were described by the associated-solutions model under the assumption that NiZr, Ni 2 Zr and Ni 3 Zr associates exist in the melt. The phase equilibria computed on the basis of the obtained thermodynamic properties and the developed model are shown to agree with available experimental information. The nature of the interparticle interaction in the Ni-Zr system was analysed and the behaviour of the thermodynamic functions accompanying the process of transition of the Ni-Zr melt into the amorphous state was considered. Quantitative agreement with the independent experimental results was obtained.

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The Knudsen-cell mass spectrometry and the integral Knudsen effusion technique under ultra-high neutral vacuum were used to study evaporation of pure Fe, Cu and molten Fe-Cu alloys containing up to 10.1 mol% Cu in the temperature range of 1 440 to 1 916 K. Standard sublimation enthalpies of Fe and Cu and thermodynamic characteristics of the Fe-Cu liquid solution were calculated. The obtained results and literature data were applied for assessment of potentialities of steel decopperizing technology based on evaporation. The time required for a decrease in Cu concentration from 0.6 to 0.3 wt% through evaporation from the exposed surface of a 160-tons ladle into vacuum of 100 Pa amounts to 5 h. Decopperizing can be accelerated by combination of vacuum treatment with blowing neutral gases through the molten metal. Two processes are responsible for removal of copper in this case: transfer into gas bubbles, free-rising from the ladle bottom to its surface, and evaporation from molten metal surface, turbulized by blowing-through gas. The length of treatment required for the above decrease in copper concentration under the most favorable conditions (the highest vacuum over the ladle and the highest velocity of gas-stream blowing through the molten metal used in metallurgy) reduces to 1.5 h.

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Knudsen-cell mass spectrometry and the integral variant of effusion method have been applied to investigate the thermodynamic properties of liquid Fe-Si-B alloys at temperatures from 1423 to 1894 K over concentration intervals of 9-88.8 at. pct Fe, 2.6-81.4 at. pct Si, and 7.5-50 at. pct B.The activity values of the components and the Gibbs energy of the Fe-Si-B melt formation have been determined over a wide temperature-concentration range. The concentration and temperature dependences of the thermodynamic functions of liquid Fe-Si-B alloy have been described adequately within the ideal associated-solution model under the assumption that binary and ternary associates exist in the melt. The relevance of the model was tested in the undercooled region. The glassforming ability of the melt as shown could be interpreted in terms of the thermodynamic parameters of the association reactions. A specific role of ternary interaction was clarified.