Role of segregation in the kinetics of abnormal grain growth in polycrystalline ceramic fibers: Phase-field modeling and experiments

In this study, we develop a multiphase-field model to describe the coupled evolution of abnormal grain growth with grain boundary segregation in polycrystalline doped- α -alumina (Nextel 610) fibers at 1300 ° C . The model treats the grain bulk and grain boundary as distinct thermodynamic phases, capturing the time evolution of dopant segregation at grain boundaries and couples these changes to the anisotropic grain boundary energy and mobility. For microstructures initialized with distinct grain boundary properties assigned to selected normal and abnormal grains, the simulations show rapid growth in the beginning followed by a marked reduction in grain-growth kinetics as Si segregation increases. Numerical tests demonstrate that the present approach remains stable at high segregation strengths and provides physically consistent concentration fields. Two-dimensional simulations reproduce the experimentally observed grain size evolution with different model variants. Three-dimensional simulations further show that diffusion along multiple boundary directions reduces local solute accumulation at junctions compared with two-dimensional simulations, while preserving the overall segregation behavior. The current segregation model, implemented within the multiphase-field framework and examined through multiple numerical variants, provides a foundation for subsequent mesoscale analyses of solute segregation and its kinetic effects across a range of polycrystalline material systems.