EARLY STAGES OF FATIGUE IN COPPER SINGLE CRYSTALS

The dislocation sub-structure and surface markings formed during the early stages of fatigue in copper single crystals at room temperature were studied. For the first few cycles the structure is similar to that associated with stage I of tensile deformation. A three-dimensional network of interconnected veins packed tightly with mainly primary edge dislocations then develops. The scale of the structure decreases with increasing strain. The surface observations show that in the first few cycles long straight primary slip lines are formed, but later the new slip markings are fine and short, their length corresponding to the inter-obstacle distance. The merits of various proposed mechanisms for fatigue are discussed. © 1969 Taylor & Francis Group, LLC.