Crystallite Rotation Experiments Revisited: the Contribution of Free-Surface Interactions

While crystallite-rotation experiments of the type pioneered by Gleiter and his co-workers have provided a great deal of information about the variation of grain boundary energy with crystal misorientation, certain aspects of the experiments still remain puzzling. Notably, crystal rotation rates do not follow the form predicted by consideration of the Read-Shockley equation; and Chan and Balluffi have shown that in some cases certain crystallites are able to escape from the energy cusps that trap others [5]. In this paper we re-examine the crystallite rotation mechanism and rotation rates from the perspective of the interactions of grain boundary dislocations with the free surfaces that terminate the grain boundary.