A universal relation for the stress dependence of activation energy for slip in body-centered cubic crystals

By analyzing experimental data in the literature, the activation energy H f or slip in body-centered cubic metals is found to approximately obey the si mple relation H approximate to 0.1 mu b(3) (1 - t)(2), where t is the appli ed stress normalized by the zero-temperature Peierls stress, mu is the [111 ] shear modulus, and b the 1/2[111] Burgers vector. Such universal relation is explained by analyzing the activation processes of kink- pair generatio n and expansion along threefold screw dislocations using the generalized Pe ierls-Nabarro model [A. H. W. Ngan, J. Mech. Phys. Solids 45, 903 (1997)]. The model also predicts qualitatively the general form of the orientation d ependence of Peierls stress at zero temperature. (C) 1999 American Institut e of Physics. [S0021-8979(99)03715-9].