On the macroscopic distribution of dislocations in single crystals of high-purity recrystallized aluminium

Abstract

Single crystals about 1 cm² in area and 1 mm thick prepared by annealing both lightly and heavily deformed zone-refined aluminium have been examined x-ray topographically. From stereopairs of various Bragg reflections the orientation and Burgers vectors of dislocations could be determined. Repetitive examination showed dislocation movements after slight deformation and also after long storage. Helices and sets of coaxial prismatic loops are seen with diameters ranging from a minimum observable value of about 1 μm to over 60 μm, and they may extend more than 1 mm along 〈110〉 directions. These features result from absorption of vacancies by long screw dislocations which, it is concluded, constituted a major part of the dislocation population grown-in during recrystallization. Dislocation densities of only a few tens per cm² are found within 200 to 300 μm of the specimen surfaces and evidence is presented that such low densities arise from loss of dislocations at the surfaces.