Journal article
Dislocation Structures in Creep-deformed Polycrystalline MgO
Secondary creep of polycrystalline MgO with grain sizes of 100 and 190 μm was investigated at 1300° to 1460°C under compressive loads of 2.5 to 5.5 kgf/mm2. The dependence of creep rate on load follows a power law with an exponent of 3.2±0.3. The process is thermally activated, with an activation energy of 76 ± 12 kcal/mol.
The creep rate is independent of grain size. The dislocation structure was investigated by transmission electron microscopy. The total dislocation density follows the relation, σ=bG√ρ, commonly found for metals. The dislocations form a 3-dimensional network in which many dislocation segments lie in their slip or climb planes.
On the basis of this structure, a model is proposed in which glide is the principal cause of deformation but the rate-limiting process, i.e. annealing of the network, is diffusion-controlled. Theoretical estimates and experimental results agree within 1 order of magnitude.
Language: | English |
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Year: | 1972 |
Pages: | 606-610 |
ISSN: | 15512916 and 00027820 |
Types: | Journal article |
DOI: | 10.1111/j.1151-2916.1972.tb13453.x |