  Nanocrystalline (NC) materials are intrinsically unstable against grain
growth. Significant research efforts have been dedicated to suppressing the
grain growth by solute segregation, including the pursuit of a special NC
structure that minimizes the total free energy and completely eliminates the
driving force for grain growth. This fully stabilized state has been predicted
theoretically and by simulations but is yet to be confirmed experimentally. To
better understand the nature of the full stabilization, we propose a simple
two-dimensional model capturing the coupled processes of grain boundary (GB)
migration and solute diffusion. Kinetic Monte Carlo simulations based on this
model reproduce the fully stabilized polycrystalline state and link it to the
condition of zero GB free energy. The simulations demonstrate the emergence of
a fully stabilized state by the divergence of capillary wave amplitudes on
planar GBs and by fragmentation of a large grain into a stable ensemble of
smaller grains. The role of solute diffusion in the full stabilization is
examined. Possible extensions of the model are discussed.
