Theoretical study of the internal friction associated with bulk diffusion of solute atoms around dislocations in Al-Mg alloys

Abstract

Abstract In this paper the anomalously amplitude-dependent internal-friction peak (the P3 peak) in cold-worked Al-Mg alloys is theoretically analysed by solving the bulk diffusion equations of the solute atoms under the action of dislocation drag in the case of a constant external stress. The results show that the bow-out distance of the dislocation has an exponential relation with time. Both the relaxation strength Δ and the relaxation time τ calculated by fitting the curves with a standard exponential creep function increase with increasing strain amplitude. The activation energy H and pre-exponential factor τ0 deduced from τ through the Arrhenius relation can be well described by a parabolic function with strain amplitude. The P3 peak is calculated from the data on Δ and τ by assuming that it obeys a standard Debye peak. The P3 peak shifts towards a higher temperature and gains in height when strain amplitude increases, which are in agreement with pertinent experiments.