Low energy dislocation structures produced by cyclic deformation

Abstract

Cyclic deformation in push-pull straining provides ideal conditions for achieving low energy dislocation structures because large cumulative strains give rise to high dislocation densities and the to-and-fro dislocation motions enhance entrapment probabilities. At low strain amplitudes the structures are dominated by clusters of prismatic loops; evidence for the dislocation content and interaction of the clusters is reviewed and is shown to be consistent with the establishment of low energy arrays. At higher amplitudes the dislocation structures are dominated by dislocation walls which are strongly dipolar. The deformation which occurs in these structures at low numbers of cycles does not seem to be consistent with low energy arrays, or at least only with those of moderately low energy. However, with sufficient cycling, lower energy arrays seem to become established and to promote homogeneity of the strain. At still higher amplitudes, complex cellular structures are observed and the complications of these structures can be interpreted convincingly in terms of low energy dislocation structures.