The dislocation structure evolution of deformation band and crack formation in a copper bicrystal with a perpendicular grain boundary

Cyclic deformation of a copper bicrystal with perpendicular grain boundary (GB) has been performed at room temperature at a constant plastic strain amplitude of 1.5×10−3. The dislocation structure evolution in typical deformation band (DB) as opposed to persistent slip bands (PSB) was observed by electron channelling contrast technique in the scanning electron microscope (SEM) at different cycles. It was found that a micro-crack nucleated preferentially at the interface between matrix and the second type of deformation band (DBII), the habit plane of which is close to the conventional kink plane {1 0 1}, in the vicinity of grain boundary (GB), and propagated along DBII. The dislocation structures of the transgranular and intergranular crack tip were also observed. The main dislocation structure near the crack tip is the cell structure.