Phase-field simulation of nano-a′ precipitates under irradiation and dislocations

This is the first investigation on the micromorphology and kinetics evolution of Cr-rich a' precipitates under Cr composition, irradiation and dislocation with the three-dimensional phase-field simulation. The statistical results of volume fraction, particle number density, and average particle size under different Cr composition are consistent with the APT re-sults. The particle density and volume fraction of a' precipitates increase with the increase of Cr composition (>9 at.%), while the mean radius decreases. Fitting the free energy curve to analyze the driving force and resistance of a' precipitates. It is found that a' precipitates preferentially nucleate in the dislocation core region due to the drive of dislocation elastic energy, while the nucleation in the dislocation free region is driven by chemical free en-ergy. Growth of a' precipitates is driven by chemical free energy and interface energy. The particle size distribution of 3dpa shows that the particle size distribution of a' precipitates becomes more uniform with the increase of dislocation density. The strengthening model calculated from the simulation results shows that the Cr component has a great influence on the strengthening, and the total strength increases slightly with the increase of dislo-cation density.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

This study investigated the micromorphology and kinetics evolution of Cr-rich a' precipitates under various conditions using three-dimensional phase-field simulation. The statistical results were in agreement with the results obtained from atom probe tomography. The density and volume fraction of a' precipitates increased with increasing Cr composition, while the average particle size decreased. The nucleation of a' precipitates was driven by both dislocation elastic energy and chemical free energy. The growth of a' precipitates was governed by chemical free energy and interface energy. The particle size distribution of a' precipitates became more uniform with increasing dislocation density. The simulation results also showed that the Cr component had a significant influence on the strengthening effect, and the overall strength slightly increased with increasing dislocation density.