Influence of dislocation networks on the relaxation peaks at intermediate temperature in pure metals and metallic alloys

Isothermal mechanical spectroscopy (IMS) experiments were performed in a 5N aluminium single crystal after 1% cold work. A relaxation peak was observed at low frequency and at about room temperature. The activation energy: HA and the limit relaxation time τ0 turned out to be 0.5 eV and 10−8 s, respectively. The peak completely disappeared after an annealing at 673 K. Transmission electronic microscopy experiments were performed in the same material at various temperatures corresponding to the ones of the damping experiments. At room temperature, the sample exhibited essentially dislocation walls. A comparison between changes in these dislocation walls and the evolution of the IMS spectra allowed to conclude that the origin of the relaxation peak was the dislocation motion inside the dislocation walls.