Abstract
It is suggested that the formation of persistent slip bands during cyclic deformation of copper single crystals occurs as the result of a transformation in an irregular dislocation microstructure (found after saturation in the harder parts of the crystal) to produce the so-called ‘wall structure’ characteristic of the slip bands. Micrographs of a specimen containing both wall and matrix structures show a definite relationship between the two on the basis of which a tentative mechanism for the transformation is proposed. The evidence presented also suggests that any theory intended to account for the wall spacing will have to be based on events occurring at, or shortly after, saturation rather than on the conditions found in the slip bands later in the test.