YIELDING AND PLASTIC FLOW IN NIOBIUM
A detailed comparison was made of the substructures and mechanical properties of polycrystalline niobium deformed at room temperature. The results show that the lower yield stress depends upon the total impurity content, and that solute atom clusters are the strongest barriers to dislocation motion. It was concluded, however, that impurities are not responsibie for the temperature dependence of the yield stress. The yield drop is shown to be due to dislocation multiplication and the effect of grain size on the yield and flow stress appears to be significant through the dislocation density. Dislocation cell structures are formed only in impure Nb containing dispersed precipitates. In the purest Nb, dislocations are uniformly distributed, and the material exhibits very little work hardening. Work hardening was thus attributed to the long-range stress fields of cell walls or tangles. Dislocations were never observed to be extended and cross-slip is an easy process in Nb. This is consistent with Nb having an intermediate or high stacking fault energy. (auth)
- Research Organization:
- Univ. of California, Berkeley, CA (United States)
- NSA Number:
- NSA-17-029339
- OSTI ID:
- 4694012
- Report Number(s):
- UCRL-10515
- Journal Information:
- Acta Met., Vol. Vol: 11; Other Information: UCRL-10515. Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- United States
- Language:
- English
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