The Bordoni Relaxation in High Purity Copper Single Crystals at Low Frequencies

Abstract
The aim of this work is to explore the low-frequency spectrum of 5N pure copper in a subresonant pendulum which allows "in situ" cycled torsion deformation and recovery. Samples were taken from the same single crystals used for ultrasonic attenuation studies in order to compare both results in an Arrhenius plot. In one sample prepared by electro-erosion, polished with nitric acid, recovered 4 hours at 650°C in preliminary vacuum and 1,4 and 9% deformed at room temperature, the spectra show a main Bordoni peak whose height increases with deformation, and additional peaks in the 40-65K range, as important as the Bordoni peak, which are due to impurities generated during the preparation of the sample. In an uncontaminated sample cut by diamond disk, polished with a mixture of nitric, phosphoric and glacial acetic acids, and water, recovered in 5.10^-6 mmHg vacuum, deformed 3 and 5%, the internal friction spectra show the main Bordoni peak as the principal effect, accompanied by a defect modulus. The study of the influence of different parameters such as the amount of deformation, the amplitude and frequency of oscillation, the temperature rate and the recoveries may be an interesting contribution to the characterization of the Bordoni peak.