Theory and simulation of microstructure evolution due to simultaneous grain boundary migration and grain rotation with misorientation dependent energy and mobility

Simultaneous grain boundary migration and grain rotation has been found to be an important mechanism of microstructure evolution in nanocrystalline materials. During evolution, the grains in microstructure undergo rotations and at times grow by coalescing with their surrounding neighboring grains. Therefore, both grain boundary migration and grain coalescence contribute in increasing the average grain size. In the present work, a detailed study of microstructure evolution due to simultaneous grain boundary migration and grain rotation is carried out by considering misorientation dependent energy and mobility through theoretical calculations and phase field simulations. These studies consider curvature driven migration and grain rotation due to viscous sliding. Theoretical studies of bicrystal and polycrystal settings show that the average grain radius during microstructure evolution due to simultaneous grain boundary migration and grain rotation grows as R∼t0.30, for misorientation dependent grain boundary energy and mobility. Finally, we discuss various topological and statistical aspects of microstructure in the presence of both grain boundary migration and grain rotation using multiphase field simulations.