Phase-field modeling of γ′ precipitation in multi-component ni-base superalloys

To simulate γ′ precipitation in multi-component Ni-base superalloys using the phase-field method, the Gibbs free energy of the γ and γ′ phases was linked to the CALPHAD method. The free energy curve and phase equilibrium compositions in this work showed good agreement with results obtained using Thermo-Calc calculation, indicating that the model was successfully coupled with the CALPHAD method. Using this coupling method, the γ′ precipitation in a quaternary Ni-Al-Re-Ta and a third-generation Ni-base superalloy TMS-75 systems were simulated. These one-dimensional simulations demonstrated the diffusion-controlled γ′ precipitation under local equilibrium with precipitation interactions. According to our atom probe microanalyses, their simulated composition evolutions were reasonable. Such a microstructure modeling technique can contribute to alloy design, process design and even lifetime assessment of high-temperature turbine blades currently in service.