Dislocation microstructures and surface morphology in fatigued fine-grained copper polycrystals

Transmission electron microscopy observations of the dislocation substructure in fine-grained copper polycrystals fatigued at room temperature were carried out to investigate the correlation between surface morphology and the underlying dislocation substructure. The results indicate that samples fatigued under constant plastic strain amplitude well into the saturation region develop a small-scale surface roughness. The volume fraction of persistent slip band (PSB)-type structures is extremely low. PSB structures formed by the dominant slip system are observed only within narrow twin grains and are associated with an extrusion-like surface profile. The results are interpreted in terms of the size effect that allows one dominant slip system to operate in the plane parallel to a coherent twin boundary.