TEMPERATURE VARIATION OF FLOW STRESS IN BODY CENTERED CUBIC METALS
Results of rate theory and electrical resistivity studies with electron beam-melted polycrystalline Nb suggest that the temperature variation of flow stress for Nb containing several hundred ppm interstitial impurities is governed by nonconservative motion of vacancy jogs in screw dislocations in the temperature range 0 to 900 un. Concent 85% C. The resistivity study indicates that vacancies are released from trapping sites and become mobile at 167 un. Concent 85% C. The height of the total energy barrier is found to be roughly 3.3 ev below 167 un. Concent 85% C and 4.1 ev above 167 un. Concent 85% C. The experimental results below 167 un. Concent 85% C are interpreted in terms of Seeger's mechanism of formation of vacancies by conservative plus nonconservative motion of jogs in screw dislocations which requires the energy to form lattice vacancies, near 3.3 ev for Nb. The additional energy above 167 un. Concent 85% C is interpreted as that required to diffuse the vacancy away from the jog so that the total energy is equal to that for self diffusion, near 4.1 ev for Nb. The temperature region just above 167 un. Concent 85% C in which the stress is relatively insensitive to temperature is interpreted as a transition between the two mechanisms and not due to Snoek ordering. (auth)
- Research Organization:
- Pratt and Whitney Aircraft, Middletown, Conn.
- NSA Number:
- NSA-17-020462
- OSTI ID:
- 4720982
- Journal Information:
- Acta Met., Journal Name: Acta Met. Vol. Vol: 11
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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