Phase-field simulation on microstructure evolution of D019 phase in γ/γ′ structure of Co–Al–W superalloys

Abstract

The morphological evolution and precipitation kinetics of γ′ and D019(Co3W) phase in Co–Al–W alloys at 900 °C have been studied by applying Phase-field method and experiment in order to understand the transformation process of γ′ phase and D019 phase. The growth processes of D019 phase and precipitation of γ′ phase under elastic fields were simulated through coupling with thermodynamics and dynamics databases. The simulation results indicate that the misfit δ ≥ 0.53% has a greater impact on γ′ particle morphology in γ/γ′ structure. Co–Al–W alloy with low Al and high W is one of the factors to promote the precipitation of D019 phase. Three stages during aging, namely the γ′ phase incubation stage, the γ′ phase fast nucleation and growth stage, and the transformation from γ′ phase to D019 phase stage can be observed with the non-constant coarsening rate that varying with the decrease of γ′ phase. The particle size distribution(PSD) during the precipitation of D019 phase is more in line with MLSW theory than LSW theory. This simulation results are in good agreement with the experiment results to help analyze microstructure evolution of Co–Al–W alloy.