The Atomic Atmosphere at the Antiphase Domain Boundary in Ni 3 Al: A Phase‐Field Study

The atomic atmosphere and formation mechanism of the antiphase domain boundary (APB) may depend on the environmental variables of the phase transformation for the L1 2 ‐structural Ni 3 Al phase, which is the first important precipitate phase for Ni‐based superalloys. Herein, a discrete phase field method is used to reproduce the complete formation process of an APB without preset restrictions. Numerical calculations are performed to classify the atomic atmosphere, and its formation mechanism is revealed by calculating and analyzing the functional properties of the driving force. The formation process shows that four types of antiphase domains survive to form the APB. The numerical calculation results demonstrate that the atomic atmosphere has the same temperature dependence for hypostoichiometric, stoichiometric, and hyperstoichiometric systems. However, Al plays two opposite roles in influencing the atomic atmosphere according to the changes in the alloy system. The positive and negative values of the driving force determine whether the atomic atmosphere is segregated or depleted, and the magnitude of the absolute value determines the atomic atmosphere level. This atomic‐scale study of nanoscale ordered domain boundaries can provide theoretical information for further understanding of these and similar interfaces in ordered precipitation‐strengthened phases.