Multicomponent Multiphase Solidification of Ni-Base Superalloys: Phase Field Simulations Coupled to Thermodynamic Databases

摘要

A Multi-Phase-Field model is applied to predict microstructure evolution and microsegregation during directional solidification of Ni-Al-Cr as the most important ternary in single-crystal Ni-base superalloys. The model addresses both the dendritic growth of the primary γ phase and the subsequent interdendntic precipitation of the γ' phase. Calculations of multicomponent phase equilibria are obtained using Thermo-Calc and a realistic thermodynamic database, either as a preprocessing tool or on-line by means of the TQ-intertace. Multicomponent diffusion is calculated according to the Fick-Onsager relations using kinetic databases of the software DICTRA. A 1D-benchmark on solidification of a Ni-Al-Cr alloy will be presented which compares an on-line coupled phase field calculation to a sharp-interface calculation using the software DICTRA. A cut-down version of the phase field model is then applied to simulate dendritic growth. The precipitation of interdendritic γ' for different cooling rates is simulated in a shape constrained version of the model.