Theory of dislocation-solute atom interactions in solid solutions and related nonlinear anelasticity

A theory for dislocation-solute atom interactions in solid solutions has been developed which allows one to calculate the nonlinear dislocation strain-amplitude-dependent internal friction. The suggested model accounts for different modes of dislocation-solute atom interactions: (i) Solute atoms distributed in the dislocation glide plane interact with the dislocation core and represent short-range obstacles for the dislocation motion; (ii) Solute atoms situated away from the dislocation glide plane create relatively weak long-range elastic stress fields, also impeding dislocation motion. We assume that dislocations move in a two-component system of obstacles which differ with respect to the thermodynamics of dislocation--point-defect interactions. Namely, dislocations overcome short-range obstacles under the combined action of applied stress and thermal energy, whereas relatively weak long-range obstacles are surmounted athermally. The model predicts a complicated multistage behavior of the nonlinear internal friction in the strain amplitude--temperature--solute concentration domain, which is in excellent agreement with recent experimental data.