THERMODYNAMIC PROPERTIES AND PHASE EQUILIBRIA IN ALLOYS OF THE SYSTEM PB – YB
DOI:
https://doi.org/10.32782/naturaljournal.5.2023.10Keywords:
method calorimetry, melts, intermetallics, thermodynamic properties, Yb, Pb, ideal associated solution model, phase equilibriaAbstract
To develop the most rational methods of obtaining and using alloys and ligatures of a certain composition, accurate information about their thermodynamic characteristics and phase equilibria in them is necessary. The method of isoperibolic calorimetry determined the partial and integral enthalpies of mixing of melts of the Pb – Yb system in the entire range of composition in the temperature range of 1 100–1 200 K. It was established that they are formed with the release of a large amount of heat: the minimum enthalpy of mixing of melts is −45,4 ± 0,8 kJ/mol and corresponds to a melt with xPb = 0,4 at T = 1 200 ± 3, with data from the state diagram of the studied system. All thermodynamic properties (Gibbs energy, enthalpy, and entropy of formation) of melts, associates in melts, and intermetallics of the Pb – Yb system were optimized and calculated using the ideal associated solution (IAS) model. The calculated activities of the components in the melts of this system show large negative deviations from ideal solutions. Calculations based on the IAS model also made it possible to establish that the values in the melts of the Pb – Yb system increase slightly with increasing temperature, but more significantly. According to the IAS model, the temperature-concentration dependences of Gibbs energies, enthalpies and entropies of the formation of melts and intermetallics were calculated, from which the coordinates of the liquidus curve of the state diagram of the studied system were obtained. The calculated and experimental data agree well with each other. As a result, complete information on the thermodynamic properties of all phases and phase equilibria in alloys was obtained, that is, a thermodynamic description of the Pb – Yb system was made.
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