Phase-field/CALPHAD methods for multi-phase and multi-component microstructuresWednesday (06.11.2019) 11:05 - 11:25 Part of:
Quantitative simulations for multi-phase and multi-component microstructures depend on an accurate description of the Gibbs free energy and atomic mobility data. CALPHAD-based thermodynamic and kinetic databases have been successfully developed for this purpose but their application is restricted to equilibrium and simple 1D calculations. The coupling between the phase field (PF) model and CALPHAD databases significantly advances the quantitative prediction of complex microstructure evolution in engineering applications. In this work, a direct coupling of the PF and CALPHAD method for ordered and disordered phases is proposed and an efficient numerical implementation within DAMASK (Düsseldorf Advanced Material Simulation Kit; damask.mpie.de) is developed to solve the resulting transport relations. A semi-analytical inversion for the general CALPHAD free energy function for multicomponent systems is derived based on a splitting of the chemical potential relation into an invertible part, treated implicitly, and non-invertible part, treated explicitly. This solution is applied to invert the transport relations in terms of the chemical potential instead of the concentration as the independent field variable, thus enabling its efficient numerical solution. The approach also inherently enforces the equal chemical potential (KKS) condition within the diffuse-interface region in the PF model. The proposed method is benchmarked for the case of multicomponent diffusion couples, compared with that from DICTRA software. And the application of the directly coupled PF/CALPHAD method in the simulation of ordered precipitates in a quaternary Al-Zn-Mg-Cu alloy is demonstrated.