The effect of temperature and amplitude on dislocation structures in cyclically deformed pure aluminium

Abstract

Pure polycrystalline aluminium specimens have been cyclically deformed at total strain amplitudes in the range 2 × 10 −4 to 1.4 × 10 −3 at temperatures of 77 K, 163 K and 223 K. Transmission electron microscopy studies of dislocation configurations have been made. Wall structures including persistent slip band ladder-type structures have been observed within limited ranges of temperature and amplitude. It has been found that wall structures are relatively unstable at higher temperatures. Significant differences in detail are found in comparison with copper in particular. For particular configurations a larger number of Burgers' vectors are observed compared with polycrystalline copper. This results in differences in the homologous temperature ranges within which particular configurations are observed, when comparing aluminium with copper, and it is suggested that this arises mainly because of differences in the stacking fault energy, which determines the stress required for dislocation intersection.