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

To simulate gamma' precipitation in multi-component Ni-base superalloys using the phase-field method, the Gibbs free energy of the gamma and gamma' 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 gamma' 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 gamma' 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.