Plasticity of an alumina bicrystal near the rhombohedral twin orientation

Abstract

A bicrystal slightly deviated from the rhombohedral twin orientation is deformed by creep so as to activate two basal slip systems in each grain. The tilt deviation in the starting bicrystal is accommodated by two parallel arrays of disconnections with the smallest twin Burgers vectors and large associated steps. Dislocations from both grains interact with the grain boundary (GB) and the tilt deviation increases by 3.6°, giving rise to an array of pure edge disconnections with no associated steps. Interfacial defects are interpreted by reactions between incoming dislocations and GB disconnections. Decompositions of dislocations into GB disconnections are followed by glide and climb of products that can annihilate or interact to give a perfect wall of edge disconnections superimposed to the twin boundary perfect structure. Owing to their large Burgers vectors, the final disconnections are always dissociated.