Accession Number : AD0808649

Title :   STRAIN AGING OF REFRACTORY METALS (TANTALUM).

Descriptive Note : Final technical rept. Jun 62-Mar 64,

Corporate Author : BATTERSEA COLL OF TECHNOLOGY LONDON (UNITED KINGDOM) DEPT OF METALLURGY AND MATERIALS TECHNOLOGY

Personal Author(s) : Eliasz, W. ; Szkopiak, Z. C.

Report Date : JUL 1965

Pagination or Media Count : 111

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)

Descriptors :   (*TANTALUM ALLOYS, STRAIN(MECHANICS)), (*AGING(MATERIALS), TANTALUM ALLOYS), IMPURITIES, DIFFUSION, ELECTRON BEAM MELTING, INTERNAL FRICTION, HIGH TEMPERATURE, OXYGEN, NITROGEN, TENSILE PROPERTIES, STRESSES, ANNEALING, DENSITY, CARBON, MOLYBDENUM ALLOYS, TUNGSTEN ALLOYS, MELTING POINT, MECHANICAL PROPERTIES, REFRACTORY METALS, ARC MELTING, VIBRATION, DYNAMICS.

Subject Categories : Metallurgy and Metallography
      Fabrication Metallurgy

Distribution Statement : APPROVED FOR PUBLIC RELEASE