• Noubary, Kaveh Dargahi
• Hötzer, Johannes
• Kellner, Michael
• Nestler, Britta
• Seifert, Hans J.
• Seiz, Marco

Abstract

In order to approximate Gibbs energy functions, a semi-automated framework is introduced for binary and ternary material systems, using CALPHAD databases. To generate Gibbs energy formulations by means of second-order polynomials, the framework includes a precise approach. Furthermore, an optional extensional step enables the modeling of systems in which a direct generation leads to the unsatisfactory results in the representation of the thermodynamics. Furthermore, an optional extensional step enables the modeling of systems, in which a direct generation leads to the unsatisfactory results, when representing the thermodynamics. Within this extension, the commonly generated functions are modified to satisfy the equilibrium conditions in the observed material systems, leading to a better correlation with thermodynamic databases. The generated Gibbs energy formulations are verified by recalculating the equilibrium concentrations of the phases and rebuilding the phase diagrams in the considered concentration and temperature ranges, prior to the simulation studies. For all comparisons, a close match is achieved between the results and the CALPHAD databases. As practical examples of the method, phase-field simulation studies for the directional solidification of the binary Ni–35Mo and the ternary NiAl–10Mo eutectic systems are performed. Good agreements between the simulation results and the reported theoretical and experimental studies from literature are found, which indicates the applicability of the presented approaches.

Topics

• impedance spectroscopy
• phase
• simulation
• phase diagram
• directional solidification
• CALPHAD