Phase field modeling of grain stability of nanocrystalline alloys by explicitly incorporating mismatch strain

Nanocrystalline materials exhibit unique properties due to their extremely high grain boundary (GB) density. However, this high-density characteristic induces grain coarsening at elevated temperatures, thereby limiting the widespread application of nanocrystalline materials. Recent experimental observations revealed that GB segregation and second-phase pinning effectively hinder GB migration, thereby improving the stability of nanocrystalline materials. In this study, a modified phase-field model that integrates mismatch strain, solute segregation and precipitation was developed to evaluate the influence of lattice misfit on the thermal stability of nanocrystalline alloys. The simulation results indicated that introducing a suitable mismatch strain can effectively enhance the microstructural stability of nanocrystalline alloys. By synergizing precipitation with an appropriate lattice misfit, the formation of second-phase particles in the bulk grains can be suppressed, thereby facilitating solute segregation/precipitation at the GBs. This concentrated solute segregation and precipitation at the GBs effectively hinders grain migration, thereby preventing grain coarsening. These findings provide a new perspective on the design and regulation of nanocrystalline alloys with enhanced thermal stability.