Plastic deformation of uranium dioxide: observation of the sub-structures of dislocations

Single crystals of uranium dioxide were deformed in compression at imposed strain rates in the temperature range of 7000C to 14000C. The crystals were oriented to promote slip over one or two slip systems of the family [100] <110> and also on the [110] <110> system. Thin films of the deformed specimens were examined by transmission electron microscopy. When [100] <110> single glide system operates, the dislocation substructure consist of numerous dipoles, their edge components lying along <110> directions. For the [100] <110> double glide system the grain boundaries and dislocation hexagonal network are observed, the complexity of which increases with the nominal strain. Dislocation arrangments consisting of extensive cellular networks of tangling dislocations and hexagonal netting were detected for [110] <110> system. The auxillary role of [111] planes on the dislocation cross slip from [100] <110> and [110] <110> system was demonstrated. Weak beam images suggest that dissociation of dislocations can occur. (Auth.)