Segmented helices in high purity aluminium

Abstract

Abstract A high density of helical dislocations has been observed in zone-refined aluminium. The specific conditions of quenching and deformation required to produce this result indicate that helices are not normally seen in pure metals, partly because of the presence of effective competing sinks and partly because of the annihilation of screw dislocations by cross-slip during plastic deformation. The helices are not circular helices but are approximately the geodesics on a right prism. The base of the prism is a rhombus, the generator is the Burgers vector b and the feces are the (111) planes containing b. This result is explained as an effect of dislocation core energy, the core energy being lowest if the dislocation lies in a {111} plane containing b, i.e. a glide plane.