In Be, the creep stress is fairly high (τ ∼ 500 MPa) and the temperature is moderate (T ∼ 700 K), so that climb is definitely in the high stress regime (Ωτ ≈ (kT/2)).
Below, a tentative interpretation of these results is given, in the frame of the low jog density approximation ( Section 8.2.2). However, in both Mg and Be, the experimental pre-exponential factors are several orders of magnitude too large, as compared to relation (8.16), and the stress-exponent of the velocity is definitely larger than unity. This can explain the experimental activation energy, provided U j = 0.37 eV. In Mg, the authors assume that x/n ≫ a, in such a way that the total activation energy, given by Eqs. The corresponding activation energy is predicted to be equal to the self-diffusion energy, which is consistent with the experimental results in Be, not in Mg. If the jog-density is close to unity, Eq. (8.16c) (high jog density approximation). The dislocation velocity expected by the authors corresponds to Eq. These results have been discussed by Edelin and Poirier, on the basis of a theoretical approach ( Edelin, 1971) that has been included in Section 8.2. From Edelin and Poirier (1973a,b) Copyright © 1973Īctivation parameters of the creep rate in Be are thus probably also characteristic of the dislocation climb velocity. Climb velocities in Mg (a) as a function of temperature, and (b) as a function of stress.
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Medically reviewed by Anthony Dugarte M.D.
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