SEM-ECC investigation of dislocation arrangements in cyclically deformed copper single crystals with different crystallographic orientations

The dislocation arrangements induced by cyclic deformation in some differen tly oriented copper single crystals were investigated using electron channe lling contrast (ECC) technique in scanning electron microscopy (SEM). It is shown that the ECC technique can well be used to examine dislocation arran gements in fatigued copper single crystals, especially at higher imposed pl astic strain amplitudes. The typical dislocation structures in the cyclical ly deformed copper single crystals detected by this technique are in good a greement with those found by transmission electron microscopy (TEM). Furthe rmore, the SEM-ECC technique shows some attractive advantages compared to T EM. For instance, ECC observation clearly reveals an evolutional process of dislocation structure from the vein structure of matrix formed at lower st rain amplitude to the labyrinth structure formed st higher strain amplitude . Moreover, the exact observations of dislocation arrangements within cycli c deformation bands (DBs), which are rather difficult to achieve by TEM, ar e successfully accomplished using the ECC method. The DBs formed in cyclica lly strained copper single crystals may exhibit quite different microstruct ures, depending upon their crystallographic orientation and accumulated pla stic strain, such as PSB ladder, wall and labyrinth structures. Finally com bining the existing TEM results with the present SEM-ECC observations, we c an state with certainty that the crystallographic orientation has a strong effect on the saturation dislocation features of copper single crystals.