Comprehensive deformation of polycrystalline UO2

The deformation of polycrystalline stoichiometric UO2 in compression exhibits a low-temperature (less than 12000C) behavior that is distinct from its high-temperature behavior. The data for both temperature regions fit either an Arrhenius equation, γ = ν exp [--ΔH/sub (tau)//RT], or the relation γ = Atau/sup n//T exp [--DELTAH0/RT]. At low temperatures, the activation energy and volume, the shape of the yield-stress-temperature curve, and the grain size-strength relation suggest a Peierls mechanism as rate-controlling in the deformation process. At high temperatures (greater than or approximately equal to 13000C), a different dislocation mechanism becomes rate-controlling for coarse-grained material, whereas very fine-grained (1 μm) material exhibits Nabarro-Herring deformation. (U.S.)