The reprecipitation and evolution of γ’ precipitates during various cooling approaches from supersolvus temperature are studied experimentally and via phase field simulation in nickel-based single crystal superalloys. The focus of this paper is to explore the influence of cooling methods on the evolution of the morphology and the distribution of γ’ precipitates. It is demonstrated that small and uniform spherical shape γ’ particles formed with air cooling method. When the average cooling rate decreases, the particle number decreases while the average matrix and precipitate channel widths increase. The shape of γ’ precipitates which changed from spherical to cubic and irregular characteristics due to the elastic interaction and elements diffusion are observed with the decrease of the average cooling rate. The phase field simulation results are in good agreement with the experimental results in this paper. The research is a benefit for the study of the rejuvenation heat treatment in re-service nickel-based superalloys.
The precipitation and evolution of γ′ precipitates for various aging heat treatment regimes are studied experimentally in Ni-based single crystal superalloys for both standard heat treatment and long-term aging samples. The focus of this paper is to explore the influence of aging heat treatment on the evolution of the morphology and the distribution of γ′ precipitates. It is demonstrated that the splitting and shrinkage phenomena appear at low aging heat treatment temperatures, and the passivation phenomenon occurs at a high aging temperature of 1200°C. The uniform cubic γ′ particles can be obtained at 1100°C/4 h for the standard heat treatment samples and 1150°C/8 h for the long-term aging ones. This research is beneficial for the study of the rejuvenation aging heat treatment in re-service nickel-based superalloys.
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