Accommodation migration of grain boundaries

This paper further explores the idea of Kocks (1970), Khayutin (1974), Poirier (1981), and Cobbold et al. (1984) that grain-boundary migration can sometimes act as a deformation mechanism. In particular it is shown how combined rotation of grains and grain boundary migration are geometrically capable of accommodating the otherwise incompatible plastic deformations that tend to arise in neighboring grains of low symmetry materials on account of their different lattice orientations. An experimental example is provided where the observed change in position of a grain boundary corresponds to the change predicted by the theory relating position of a coherent deformation domain boundary to the deformations either side of the boundary. Further observation of deformation fields near mobile grain boundaries is required, however, to establish whether or not "accommodation migration" is ever an important phenomenon. Meanwhile, the theory of coherent boundaries explained here and in Cobbold et al. (1984) can also be applied to other problems, for example, to the study of dynamic recrystallization by progressive misorientation of subgrains, or to the study of deformation-induced phase changes.