DISLOCATION RELAXATION IN SILVER SINGLE-CRYSTALS AT MEGAHERTZ FREQUENCIES

The Bordoni peak in high-purity silver single crystals has been invest igated by measuring the attenuation of longitudinal waves of 5, 10 and 30 MHz, using a conventional ultrasonic pulse technique with single q uartz transducer. The crystals, of [100], [110] and [111] orientations , were deformed by compression, and the temperature-dependent ultrason ic attenuation was measured after applying resolved shear stresses ran ging up to 60 N mm(-2). The results lead to the following conclusions: (i) the temperature of the Bordoni peak in silver single crystals is essentially independent of the orientation; (ii) the temperature of th e Bordoni peak in silver single crystals decreases as the prior deform ation is increased up to resolved shear stress near 28 N mm(-2), and t hen increases for higher prior stresses; (iii) the Bordoni peak height decreases as the frequency increases and (iv) the Bordoni peak height increases with increasing the amount of deformation.