Grain growth rate for coupled grain boundary migration and grain rotation in nanocrystalline materials

Grain rotation has been found to be an important mechanism of microstructure evolution in addition to curvature-driven grain boundary migration in nanocrystalline materials. Grains coalesce due to rotation and this provides an additional mechanism of grain growth. We show that for growth by coupled migration and rotation coalescence the average grain size grows as indicating that the coupled problem is surprisingly more stable to grain growth. We then present an appropriate rotationally invariant multiphase field model which accounts for grain rotation to corroborate the theoretical result.