Publication details

Modelling of tau phases in the Al-Cu-Zn system



Year of publication 2022
Type Conference abstract
MU Faculty or unit

Faculty of Science

Description We have performed a combined theoretical and experimental study of two allotropes of the tau phase in the Al-Cu-Zn system. Quantum-mechanical calculations and CALPHAD modelling were employed in combination with experimental data (SEM, DTA, XRD) [1]. Thermodynamic, structural and elastic properties have been investigated in the case of both rhombohedral and cubic allotropes of the tau phase. The supercell approach was used to model the composition Al13Cu10Zn2 with 1/6 of the total number of atomic positions vacant. The quantum-mechanical calculations performed using the VASP code provided the energies of formation of the end-members of the rhombohedral tau phase, which form the solid base for the phase-diagram modelling. The rhombohedral allotrope reveals higher stability with respect to the fcc phases of Al, Cu, and Zn than the cubic one. The volume of the cubic phase is bigger than that of the rhombohedral phase by 0.54 %. Elastic constants of both allotropes indicate their significant elastic stiffness. Furthermore, the stability and vibrational entropy of the cubic and rhombohedral modification of this phase were studied using phonon-spectra calculations within the quasi-harmonic approximation resulting in the temperature dependence of the total Gibbs free energy, equilibrium volume, heat capacity, bulk modulus, etc.
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