Comments on the paper “Influences of crystallographic orientations on deformation mechanism and grain refinement of Al single crystals subjected to one-pass equal-channel angular pressing”

Han et al. [W.Z. Han, Z.F. Zhang, S.D. Wu, S.X. Li, Acta Mat. 55 (2007) 5889–5900] have published a paper about equal-channel angular extrusion (ECAE) testing of Al single crystals. It is shown in this work that their paper contains numerous errors in both presentation and interpretation of the results. The main experimental error concerns the initial orientations of the crystals that are far from their assumed orientations, while the theoretical discussion is faulty in terms of the deformation mechanisms that apply in ECAE processing. It is also shown that the use of the so-called “shear factors” can lead to erroneous results related to the identification of the active slip systems in simple shear.