Complications of diffusional creep at very small grain sizes
- State Univ. of New York, Stony Brook, NY (United States). Dept. of Materials Science and Engineering
In the bulk diffusional creep model developed by Herring and Nabarro, and in Coble's grain boundary diffusional creep model, grain boundaries are presumed to be perfectly efficient sources of sinks for point defects. Although occasionally controversial, these models have provided accurate descriptions of the deformation of polycrystalline materials at high temperatures and low stresses, at least for materials of conventional grain size. In appropriate regimes of temperature, stress and grain size, either Herring-Nabarro or Coble creep are usually identified as the primary mechanism of deformation. Some experiments at very low stresses, however, have identified a threshold stress, [sigma][sub t], below which no deformation occurs. This is associated with barriers to point defect absorption or emission at the grain boundaries, and its effect upon measured creep rates is usually too small to be significant. It is the purpose of this paper to consider the possible effects of the threshold stress in the extreme conditions of very fine grained or nanocrystalline material. The authors note that a recent paper has identified departures from the Herring-Nabarro and Coble models in a nanocrystalline Ni-P alloy.
- OSTI ID:
- 6935193
- Journal Information:
- Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 31:11; ISSN SCRMEX; ISSN 0956-716X
- Country of Publication:
- United States
- Language:
- English
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