Two-step low-cycle fatigue tests of pure single crystals in a single-slip orientation were performed in pull-push mode under a constant plastic strain amplitude. In the first step of the tests, plastic strain amplitudes which were larger than those in the plateau region of the cyclic stress-strain curve were applied. In the second step, lower plastic strain amplitudes in the plateau region were applied. In the first step, the stress amplitude exhibited cyclic hardening up to saturation. The stress amplitude in the second step gradually decreased with increasing cumulative plastic shear strain, and transformation of the dislocation structure occurred. Well-developed cell and labyrinth structures, present after the first-step tests, changed into a ladder structure that was characteristic of the formation of persistent slip bands. The ladder structure started to form in the early stages of the second-step test and the dislocation wall spacing of the ladder structure gradually increased with increasing cumulative shear strain. It was concluded that the cell and

labyrinth structures rearranged into a persistent slip band ladder structure upon reducing the plastic shear strain amplitude.

Rearrangement of Fatigue Dislocation Structure in Copper Single Crystals Associated with Reduction in the Plastic Strain Amplitude. C.Watanabe, K.Kanmuri, M.Kato, S.Onaka, T.Fujii: Philosophical Magazine A, 2002, 82[7], 1317-30