Polycrystalline specimens of 6N-purity material were tested by means of isothermal mechanical spectroscopy. Experimental results confirmed the existence of a low-temperature effect, and of a relaxation peak at intermediate temperatures; usually denoted by P'1 or P1. Isothermal experiments, performed as a function of frequency, permitted the study of the evolution of these relaxation effects with the measurement and annealing temperatures, and provided evidence for the unusual behaviour of P1. It was concluded that this peak was not associated with the classical thermally-activated relaxation peak. The results were explained in terms of dislocation motion within a tangled microstructure.

Anomalous Internal-Friction Peaks Observed in Very-High-Purity Aluminium. A.Rivière: Philosophical Magazine A, 2001, 81[8], 1887-900