The distribution of dislocation walls in the early processing stage of equal channel angular extrusion

The spatial distribution and misorientations of the dislocation walls formed in pure aluminium after the first three passes of equal channel angular extrusion (ECAE) was investigated by transmission electron microscopy (TEM). Our observations indicate that the distribution of those dislocation walls having relatively higher misorientations (>3°) can be related to the macroscopic shear imposed by each extrusion pass. A significant fraction of these “high angle” dislocation walls formed by the first pass were stable walls; further extrusion passes sheared them to the new orientations according to the amount of the shear strain and the process route used.