Theory of the nonlinear internal friction associated with bulk diffusion of solute atoms around dislocations in Al–Mg alloys

Abstract

In this paper the nonlinear (amplitude-dependent) internal friction (P 3 peak) in cold-worked Al–Mg alloys is theoretically studied by solving the bulk diffusion equations of the solute atoms (Mg atoms) under the action of dislocation drag. The results in the case of a constant external stress show that the bow-out distance of the dislocation has an exponential relation with time, which can be well described by an exponential creep function with a Gaussian distribution in τ. With the increasing strain amplitude, the relaxation strength Δ and relaxation time τ decrease, while the distribution parameter increases. Both activation energy H and pre-exponential factor τ 0 deduced from τ through Arrhenius relation are dependent on strain amplitude.