Plastic deformation of single crystal UO/sub 2 + x/
Single crystals of UO/sub 2 + x/ (2.000005 less than or equal to O/U less than or equal to 2.1) were deformed in equilibrium CO/CO/sub 2/ mixtures at 873, 1273 and 1673K along two compression axes (111) was the primary glide plane at 873K (and at 300K under microhardness indents) regardless of O/U ratio, while at 1273 and 1673K the primary glide plane was a function of O/U ratio. At low O/U ratios (100) was the primary glide plane, while (111) was the primary glide plane for O/U greater than or equal to 2.01. At 1273 and 1673K glide was controlled by long range defect-dislocation interactions, presumably due to the increased mobility of defects. The softening of specimens deformed by glide on or nearly on (111) planes with increased O/U ratio at 1273 and 1673K was related to the reorientation of oxygen interstitial defect complexes in dislocation stress fields, and may be caused by the ability of these defects to scavenge impurity defects and reduce the resistance to glide. Macroscopically noncrystallographic slip was commonly observed at 1273 and 1673K, where slip traces were seen which indicated that glide had occurred on combinations of (111)-(110) and (111)-(100) planes. This noncrystallographic slip was a consequence of cross-slip of screw dislocations between highly stressed slip systems, and evidence of such cross-slip was commonly observed in TEM at all temperatures. In general, the dislocation substructure showed little dependence on O/U ratio; however, there appeared to be a fundamental difference between specimens deformed at 873K and those deformed at 1273 and 1673K. At 873K the substructure consisted of jogged screw dislocations and a high density of small (< 200 nm) nearly edge loops, while at the higher temperatures, mixed dislocations, often not on the glide plane, and large (1-2..mu..M) nearly edge loops dominated the substructure.
- Research Organization:
- Case Western Reserve Univ., Cleveland, OH (USA)
- OSTI ID:
- 6249936
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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