Equal Channel Angular Extrusion (ECAE) has been used to produce sub-micron-size grain structures in two aluminium alloys (AA1200 and AA31303). The ECAE was attempted at room temperature and following the so-called route C. The process via route C involves a 180degrees angular rotation in between each pass and it strongly affects the material microstructure by reversing the shear strain every second pass. This particular and unique characteristic of the route C induced a limited build-up of significant numbers of new high angle boundaries, at least for the first three passes, which the present proposed paper has been focused to. 3 passes by route C throughout the ECAE die were sufficient to produce a very fine structured material for both 1200 and 3103 alloys. High resolution EBSP analysis has been carried out to measure the boundary misorientation within the deformed structures. Yet, the sub-grain and grain spacing has been measured revealing a faster refining effect on the 3103 alloy respect to the 1200 ones.