Analysis Of Dislocation Structures In Fatigued Aluminium Single Crystals Exhibiting Striations

Aluminium single crystals were fatigued at low strain in an orientation leading to the development of striations (persistent slip bands) and the internal dislocation structures examined by transmission electron microscopy. At an intermediate stage of fatigue damage, direct correlation of the surface deformation markings and the underlying dislocation structure was achieved from the examination of surface foils. Structures associated with striations and features in the matrix regions of the crystals were identified. Information obtained from slip traces on the crystal surface has been combined with that from Burgers vector analysis of the underlying structure and possible mechanisms considered. The examination of foils prepared from the interior of the crystals confirmed that the structures associated with surface features were also present at all depths within the crystals. A change in the dislocation structure was found to occur as the number of fatigue cycles was increased and this was studied between 170 cycles and 8 × 105 cycles.