Thermodynamic assessment of the phase equilibria and prediction of glass-forming ability of the Al-Cu-Zr system

The thermodynamic description of the Al-Cu-Zr system was performed using the CALPHAD method. The solution phases liquid, fcc, bcc and hcp were described using a substitutional solution model. The compounds in the Al-Zr and Cu-Zr systems and the ternary compounds τ3, τ5, τ7 and τ8 were treated as a line compound in the Al-Cu-Zr system. The ternary compounds τ1, τ2, τ4, τ6, τ9 and τ11 were described as a stoichiometric compound. The enthalpies of mixing of the liquid phase at different temperatures and compositions, two invariant reactions, and five isothermal sections at 773, 873, 1073, 1273 and 1373 K were taken into account in the present optimization work. A set of self-consistent and reliable thermodynamic parameters of the Al-Cu-Zr system was obtained. By searching the local minimum of the driving force for crystalline phases under the supercooled liquids, the thermodynamic parameters obtained in this assessment were later used for predicting composition dependencies of high glass-forming ability in the Al-Cu-Zr system. The predicted alloy compositions of high glass-forming ability are in satisfactory agreement with the available experimental data.