Thermophysical properties in the Al-Cu-Ag system: A combined CALPHAD and first-principles study

Thermophysical properties play an essential role in the microstructure simulation during precipitation and solidification processes in materials science and engineering. In this work, a comprehensive investigation on the molar volume and surface tension of the Al-Cu-Ag ternary system was performed by the CALPHAD (CALculation of PHAse Diagram) approach and the first-principles calculation. Based on the critical review of experimental and theoretical data, the molar volume description of pure Ag in the liquid phase, and subsequently the mole fraction dependent thermophysical databases of molar volume and surface tension for the Al-Cu-Ag system including metastable phases were constructed via the CALPHAD approach. Then considering the excess molar volume, the surface tension of solution alloys could be predicted by the Butler equation using a home-made code with the input of thermodynamic and thermophysical parameters. With the increment of temperature, molar volume of the alloys increases while the surface tension decreases. All the calculated results using the present parameters are in satisfactory agreement with the corresponding experimental data, which could be subsequently applied to simulate the microstructure evolution like precipitation kinetics and phase-filed simulation.