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Description
This work is focused on a theoretical study of the phase stability of solid solutions in Al-Ge, Al-Pb, Ag-Ge and Ag-Pb alloys, in which there are no intermediate phases across the whole composition range. The solubilities of these alloys were determined using temperature-dependent free energies of pure elements and respektive Al- and Ag-rich solid solutions obtained from ab initio calculations based on density functional theory (DFT). Contributions of vibrational free energy from phonons, electron free energy and configuration entropy were included to the free energy. The quasi-harmonic approximation was employed to include also the effect of volume expansion.
The main focus of this work is the Al-Ge alloy, while the other examined alloys
serve the purpose of comparison of the solid solubility predictions. The temperatures, at which the solid solutions with 3 at. % of doping element become stable, were estimated from the energy difference between possible states. The temperatures were compared to the experimental ones in phase diagrams provided by the CALPHAD method. The succession of temperatures for all studied alloys very well corresponds to the experimental measurements. However the exact temperature values are underestimated.
