The influence of grain size on the creep of uranium dioxide |
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Authors: | B Burton G L Reynolds J P Barnes |
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Affiliation: | (1) Berkeley Nuclear Laboratories, Central Electricity Generating Board, Berkeley, Gloucestershire, UK |
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Abstract: | The creep of uranium dioxide has been investigated as a function of grain size. At high stresses, when creep is controlled by dislocation movement, grain boundaries exert a strengthening effect and this strengthening is correlated with the Hall-Petch equation. The degree of strengthening diminishes with increases in temperature. At lower stresses, when creep is controlled by mass transport, grain boundaries exert a weakening effect owing to the reduction in diffusion path length as grain size is reduced. In this range behaviour is correlated with the Nabarro-Herring equation with stress replaced by an effective stress
E= – 0 where
0 is a threshold stress for diffusional creep associated with the limitation of the ability of boundaries to emit and absorb vacancies.
0 appears to decrease as grain size is increased. |
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