Severe plastic deformation: simple shear versus pure shear

The paper analyzes an effect of deformation mode on structure evolution under severe plastic deformation. From a continuum standpoint, all possible strain states range from pure shear to simple shear and can be described by a single parameter. The microstructure evolution at large strains is linked with successive steps of continuous flow and flow localization. It is shown that simple shear conforms to the optimal deformation mode for development of spatial networks of high angle boundaries and fine grains during flow localization both for monotonic loading and cross loading. Using this approach, different deformation techniques for simple shear processing are considered with the emphasis on equal channel angular extrusion. (C) 2002 Elsevier Science B.V. All rights reserved.