The Development of the Dislocation Structures during the Fatigue Process of F.C.C. Single Crystals

Abstract

AbstractIn recent years the dislocation arrangements in the mechanical saturation stage have been studied to a great extent. In the present work the development of the dislocation arrangements in the range of cyclic hardening are dealt with in relation to the mechanical behaviour, giving special attention to the development of persistent slip bands (PSBs). The description of the dislocation structure development is related to the shape changes of the mechanical hysteresis loops.Above a cycle number Nn a set of about 1 μm long dislocation dense regions (“rungs”) aligned along the primary slip direction can be discerned. From these first rungs the ladder‐like structures of PSBs develop until the saturation. Beside the PSB structure the matrix structure changes markedly between Nn and mechanical saturation.In amplitude changing tests another mechanism of PSB nucleation is observed, namely the breaking up of the existing matrix dislocation structure by “cords”.