Abstract
The high creep resistance of dispersion-strengthened metals is the result of a threshold stress, which is determined in existing models by considering the interaction of a single dislocation with dispersoids. This paper presents a new model which takes into account the effect of dislocation pile-ups upon the detachment threshold stress of dispersion-strengthened metals. First, it is shown that dislocation pile-ups are expected to form at dispersoids when the volume fraction and/or size of the dispersoids is large. Then, the equilibrium dislocation positions within the pile-ups are calculated and the resulting shear stress exerted upon the detaching dislocations pinned at the dispersoids is determined. Finally, this pile-up stress is added to the athermal detachment threshold stress determined with existing models to find a total threshold stress. Calculations for aluminum containing 25 vol.% alumina dispersoids show that the magnitude of the pile-up stress is comparable to the athermal threshold stress, and thus contributes significantly to the total threshold stress. The model also predicts a creep activation energy much higher than that of the unreinforced metal as a result of the temperature dependence of the number of dislocations in the pile-ups.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 4569-4581 |
| Number of pages | 13 |
| Journal | Acta Materialia |
| Volume | 45 |
| Issue number | 11 |
| DOIs | |
| State | Published - Nov 1997 |
Funding
Acknowledgements-This research was supported by the National Science Foundation under grant No. DMR 9417636, with Dr B. McDonald as monitor. The authors also acknowledge the support of the Department of Defense (in the form of a National Defense Science and Engineering Graduate Fellowship for AMJ) and AMAX (in the form of an endowed chair at MIT for DCD).
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Polymers and Plastics
- Metals and Alloys