Dislocation glide in UO2single crystals at 1600°K

Abstract

Abstract A study has been made of the effects of crystal axis orientation on the slip behaviour, at 1600°K, of compressively deformed uranium dioxide single crystals. It is shown that the critical resolved shear stress for slip is anisotropic, and that the stress is sensitive to ionic configurations at the dislocation core. The morphology of slip on ‘easy’ and ‘difficult’ systems is markedly dissimilar and is a function of the ease with which dislocations are able to cross-slip from the primary glide plane. Slip in many cases is macroscopically non-crystallographic, deformation taking place by a composite slip process. In these cases slip on the primary system may be limited by dislocation interaction and the rate-controlling stress is that on the cross-slip plane. Dislocation multiplication and slip-band growth on {001} planes is limited by the unusual dislocation mobility behaviour on these planes. Fracture can be initiated at the intersection of glide bands on {011}〈011〉 systems in UO2. In this case the fracture plane is {001}.