Dislocation Mobility in Copper and Zinc at 44°K

Abstract

The torsion technique for dislocation mobility studies in close-packed metallic crystals developed by Pope, et al. (1) was first extended to low temperatures by Gorman, et al. (2). With this method, dislocation displacements are observed by x-ray diffraction on a crystal surface which was previously bonded directly to the torsion machine. Therefore a bonding agent must be utilized which is sufficiently strong to transmit the torsional stress pulse but pliable enough to prevent damage to the very soft test crystal. Various mixtures of organic solvents were found to have suitable properties when cooled to their glass-transition temperatures, and with these bonding agents mobility experiments were extended down to 66°K (2, 3, 4, 5). The torsion tests were carried out in an apparatus in which the test crystal could be cooled to any temperature down to the freezing point of nitrogen.