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

Nonlinear internal friction peaks associated with the interaction between dislocations and point defects are experimentally studied in cold-worked Al–Mg solid solutions. It is found that the appearance of these peaks is very sensitive to the cold-work methods among which the stretching method in the strain range of several percent is effective for reproducing the peaks. A maximum of the internal friction vs. strain amplitude at a given temperature around the peak is observed. With the forced vibration method and by using a nonlinear fitting program to subtract the background, the activation energies are measured to be 1.3, 1.1 and 0.7 eV, respectively, for the three peaks (PL1, P1ʹ, P1ʹʹ) in the order of ascending temperature.