I. О. Gilev, А. B. Shubin, P. V. Kotenkov.
ABSTRACT
The thermodynamic characteristics of aluminum-yttrium melts were studied. The thermodynamic properties ( ΔfH0298, S0298, (H0298 – H00), cp(T) и cp(liq)) of Al3Y, Al2Y, AlY, Al2Y3, AlY2 compounds were calculated and analyzed. The values of the standard enthalpies of formation for intermetallic compounds were calculated using the semiempirical Miedema model, and were equal to -49.4, -60, -63.4, -55, -46.5 (kJ/mol×at) for each of the intermetallic compounds, respectively. The calculations results were used in the thermodynamic modeling (TM) of the Al-Y melts. The «TERRA» software package was used as a calculation tool for TM. The model of ideal solutions of interaction products (ISIP) was used as a calculation model in the process of modeling the composition and thermodynamic characteristics of melts. The simulation was carried out in an initial argon atmosphere at a total pressure of 105 Pa. The range of temperatures and concentrations corresponding to the liquid state of this system (1900–2100 K) were investigated. A comparison of the results obtained with the results of modeling in the approximation of an ideal solution made it possible to determine the excess integral thermodynamic characteristics (enthalpy, entropy, Gibbs energy) of the Al-Y melts. It was shown that the absolute value of enthalpies of mixing regularly decreases with increasing the temperature. The obtained values were compared with the known experimental data on the integral enthalpies of mixing for aluminum-yttrium melts. The tendency for the strongest interaction of the components in this system in the entire concentration range was demonstrated by the data obtained on the basis of the calculation methods used in this work. The value of the integral enthalpy of mixing reaches -59.6 kJ/mol. The energy curves obtained as a result of TM pass through an extremum at XY = 0.46, the composition at this value is close to the composition of the AlY intermetallic compound. Experimental data indicate a lesser interaction of components, the extremum is located at the level of -49.6 kJ / mol. The data obtained in this work are in satisfactory agreement with the experimental data, the ISIP model used for TM made it possible to adequately describe the thermodynamic properties of the aluminum-yttrium melts.
KEY WORDS:
melt, aluminum, yttrium, associates, intermetallic compounds, standard enthalpy of formation, excess thermodynamic functions.
DOI: 10.31857/S0235010621050054