Internal friction in F.C.C. alloys due to solute drag on dislocations. - I. : A model for the effect of core diffusion

Abstract

The internal friction (mechanical loss) behavior of dislocations is studied in a model which, for the first time, considers the substitutional solute mobility in the dislocation core to be higher than in the bulk around it. The parameters investigated include the external stress sigma xy, the solute concentration c0, the pinning length of the dislocation and the temperature. It is shown that, at low c0 and high sigma xy, the kinetics of the dislocation motion is determined by the fast diffusion of the solute atoms in the core, while for high c0 and low sigma xy, the diffusion of the atoms far away from the dislocation is rate-limiting. The results are compared with the analytica model of Schoeck and are applied to the alloy system Al-Si. New experimental results supporting the model are described in a companion paper (Paper II).