STRAIN AGING OF REFRACTORY METALS (TANTALUM).
Abstract
Strain aging effects in electron-beam refined tantalum have been studied using the yield point return and internal friction technique. The results have been discussed with reference to current theories of strain aging. A comparison of the data obtained by both techniques has been made which shows that the internal friction technique yields more direct information about the interstitial impurity responsible for the strain aging process. Electron-beam refined tantalum, when tested at room temperature, shows strain-aging effects, which become measurable at aging temperature greater than about 70 C. The activation energy of the strain-aging process has been found to be 26,000 + or - 1,000 cal/mol which is of the order of the activation energy for the diffusion of oxygen in tantalum (25,500 cal/mol). The magnitude of the strain-aging effects have been shown to be dependent on the concentration of oxygen, and this appears to be due to increased strength of pinning of dislocations with increasing oxygen content. The increase in the yield stress caused by strain-aging has been found to be no only due to the change in dislocation locking parameter, k sub y, but also to the increase in flow stress. It has been shown that in the temperature range studied (100 - 200 C) oxygen is responsible for the strain-aging effects. At higher temperatures nitrogen and/or carbon can contribute to strain-aging too. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1965
- Accession Number
- AD0808649
Entities
People
- W. Eliasz
- Z. C. Szkopiak