THERMALLY-ACTIVATED DEFORMATION OF THE BODY CENTERED CUBIC METALS AT LOW TEMPERATURES
AEROSPACE CORP EL SEGUNDO CA
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The activation energy H, activation volume v, and frequency factor nu for the deformation of Group VAV, Cb, Ta and Group VIACr, Mo, W metals were determined as a function of the thermal component of the stress, tau, from data in the literature on the interrelationship of stress, temperature, and strain rate. It was found that H0 tau app to 0 0.1 mu b cubed, where mu is the shear modulus and b is the Burgers vector. Also, v app to 50 b cubed at tau 2 kgsq mm, increasing rapidly to values in excess of 100 b cubed at lower stresses and decreasing to 2 - 5 b cubed at high stresses, and nu 10 to the 4th power 10 to the 11th power 1sec. The activation energy and volume as a function of stress were independent of structure, indicating that the rate- controlling mechanism for the deformation of body centered cubic metals is overcoming the Pei erls-Nabarro force. TPERIMENTA DATA WERE IN AGREEMENT WITH Seegers model for the thermally activated nucleation of kinks. The kink energy and the Peierls-Nabarro energy and stress derived from the data were 3 - 4 x 1 100 mu b cubed, 2 - 4 x 11000 mu b cubed and 0.6 - 1.5 x 1100 mu, respectively.
- Metallurgy and Metallography
- Solid State Physics