On evaluating the flow stress in niobium of commercial purity
- Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering
An analysis has been made of the CP niobium data presented in two papers by J.F. Fries, B. Houssin, G. Cizeron and P. Lacombe, Jour. Less-Com. Met. 33, 117 (1973) and J.F. Fries, C. Cizeron and P. Lacombe, Rev. Phys. Appl. 5, 371 (1970). This study involves a phenomenological procedure which assumes a rate controlling mechanism in which the force between a barrier and a mobile dislocation element varies inversely as the distance. The derived analytical curves obtained with this model are in very good agreement with all the experimental flow stress and strain-rate sensitivity data from 20 to about 600 K. This agreement supports the hypothesis that, in this particular CP niobium, the rate controlling mechanism might involve dislocation intersections where it is generally accepted that the force between an obstacle and a dislocation element varies inversely as the distance. The derived analytical curves obtained with this model are in very good agreement will all the experimental flow stress and strain-rate sensitivity data from 20 to about 600 K. This agreement supports the hypothesis that, in this particular CP niobium, the rate controlling mechanism might involve dislocation intersections where it is generally accepted that the force between an obstacle and a dislocation element varies inversely as the distance between them. An analysis of the effect of the interstitials on the shape of the flow stress-temperature curve was also made for specimens tested above 300 K. It was found that the unusual flow stress peak that appears in the plateau region at 570 K might be explained in terms of overlapping of the dynamic strain aging stresses of the three interstitials O, C and N near 570 K. That the phenomenological model is not in agreement with the experimental data above 600 K is possibly due to dynamic recovery off the metal`s substructure.
- OSTI ID:
- 55328
- Journal Information:
- Acta Metallurgica et Materialia, Journal Name: Acta Metallurgica et Materialia Journal Issue: 5 Vol. 43; ISSN 0956-7151; ISSN AMATEB
- Country of Publication:
- United States
- Language:
- English
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