REARRANGEMENTS IN THE SYSTEM OF GRAIN BOUNDARY DISLOCATIONS AND MIGRATION OF GRAIN BOUNDARIES

Abstract
The dislocation structure and behaviour of grain boundaries in a low strained nickel alloy under slow and fast continuous heating was studied. It is established that the processes of grain boundary migration and dissociation of grain boundaries start (on a macroscale) not with the disappearance of electron microscopic contrast due to extrinsic grain boundary dislocations, but at higher temperatures corresponding to active rearrangements of lattice dislocations within the grain volume. Boundaries of anomalously coarse grains are characterized by an intensive twinning during their motion and the motive forse of boundary dissociation is associated with the presence of the products of dissociation of the extrinsic grain boundary dislocations in the boundary. With the growth of the rate of continuous heating the processes of dislocation rearrangements both in the grain boundaries and within the grains would shift in the high-temperature area and the anomalous grain growth is suppressed.