The fatigue of single crystals which were oriented for single slip was studied by using electron channelling contrast imaging in a scanning electron microscope. This permitted the detection and characterization of dislocation structures in bulk specimens. Images were presented here which revealed dislocation arrangements that were associated with intrusions, extrusions and stage-I and stage-II cracks in monocrystalline samples which had been fatigued in tension-compression along [541]. The presence of intrusions or stage-I cracks on the persistent slip band planes did not lead to any noticeable changes in the local dislocation structures in the matrix vein and persistent slip band ladder-structures. Stage-II cracks deviated from the persistent slip band planes, and were associated with elongated dislocation cells that were inclined in the direction of the loading axis. These elongated dislocation cells were confined to within 10µm of the crack tip.

Electron Channelling Contrast Imaging Characterization of Dislocation Structures Associated with Extrusion and Intrusion Systems and Fatigue Cracks in Copper Single Crystals. J.Ahmed, A.J.Wilkinson, S.G.Roberts: Philosophical Magazine A, 2001, 81[6], 1473-88