An anomalously amplitude-dependent internal-friction peak (P3) in cold-worked alloys was analysed theoretically by solving the equations for the bulk diffusion of solute atoms in the presence of dislocation drag under a constant external stress. The results showed that the bow-out distance of the dislocation exhibited an exponential time-dependence. Both the relaxation strength and the relaxation time, as calculated by fitting the curves using a standard exponential creep function, increased with increasing strain amplitude. The activation energy and pre-exponential factor, as deduced from the Arrhenius relationship, could be described by a parabolic function. The P3 peak was calculated from data on the relaxation strength by assuming that it obeyed a standard Debye peak behaviour. The P3 peak shifted towards a higher temperature, and increased in height when the strain amplitude was increased; in agreement with experiment.

Theoretical Study of the Internal Friction Associated with Bulk Diffusion of Solute Atoms around Dislocations in Al-Mg Alloys. Q.F.Fang, R.Wang: Philosophical Magazine A, 1999, 79[12], 2877-86