Low-frequency internal friction and elastic moduli were measured as functions of temperature, at various strain amplitudes, in wrought alloys after quenching and after aging. The damping spectrum exhibited a relaxation peak which was located at about 420K in over-aged specimens. This damping peak, with an activation enthalpy of 1.57eV and a limiting relaxation time of 2.6 x 10-19s, was attributed to the dragging of solute atoms by dislocation loops. A strong damping-amplitude effect was observed at lower temperatures. This phenomenon, which led to a high damping capacity at high strain amplitudes, was attributed to a breakaway mechanism. Damping was suggested to be due to an increase in the dislocation loop length by depinning, and to the work done in overcoming the binding energy between dislocations and solute atoms.

Mechanical Loss Spectrum of Aged Al-Mg-Si Alloys. C.Xie, E.Carreño-Morelli, R.Schaller, Y.Pitton, R.C.Fornerod: Philosophical Magazine A, 2001, 81[9], 2149-60