The influence of geometry on grain boundary motion and rotation

Recent theoretical and simulation studies indicate that grain boundary motion is coupled to the translation and rotation of the adjacent grains. However, the geometry of the system can strongly modify this coupling. We simulate the evolution of grains in two geometries that are similar to experimental systems that have been studied. The first, a small circular grain embedded in a matrix consisting of two other grains, shows that rotation can be suppressed by geometric frustration, but the coupling slows the grain boundary motion. The second, a bicrystal cut into a wedge shape, shows that free boundaries can act as sinks for grain boundary dislocations thereby stopping or even reversing the rotation caused by grain boundary motion. These results show that an experimentally relevant theory of grain boundary motion needs to consider the effects of microstructure and sample geometry.