Physical origin of surface slip morphologies induced by regular self-organized dislocation patterns in fatigued copper single crystals

In this study, the formation mechanisms of typical dislocation patterns in fatigued copper single crystals were systematically investigated and summarized. The formation of persistent slip band (PSB) ladders depends on the width of extended dislocation and the trap distance of dipole. When the actual capture distance d(trap) is less than the critical capture distance d(critical), a group of relatively stable multipoles are obtained from many dipole segments, followed by the formation of the veins and PSB-ladder structures. Further evolution will bring about more and more ladder-like PSBs appearing in one local zone until 100% PSB, which is corresponding to the formation of developing deformation bands (DBs), and then the developing DBs will be converted into the well-developed DBs by merging ladder-like PSBs. After the secondary fatigue, the veins, PSB ladders, or walls can be regarded as the nucleation source of new slip bands (SBs). No matter how the surface slip morphologies change, the evolution of dislocation patterns always keeps the dynamic equilibrium and essentially reflects the constant deepening of strain localization. (C) 2014 AIP Publishing LLC.