Modelling texture evolution in equal channel angular extrusion of bcc materials: effects of processing route and initial texture

摘要

A modelling investigation of texture evolution in equal channel angular extrusion (ECAE) of bcc materials with a 90 degrees die via routes A, BA, Bc and C is performed using a visco-plastic self-consistent model and assuming idealized simple shear deformation at the intersection plane of the die channels. For each route, the effect of initial texture on texture evolution is examined by simulations from a random, sheet or wire initial texture. The characteristic orientation fibres as found in a single pass are also evident in the multi-pass textures, but the orientation distributions along the fibres are more complete in route A than in the other routes. The initial texture effect persists in the cross shear routes, more so in route A than Bc and then BA, up to four to five passes, and afterwards the effect is insignificant and mainly on the texture strength. In route C, however, the initial texture effect remains for every pass studied due to the cyclic shear reversal in every two passes and thus there is retention of the initial texture after even-numbered passes, but as discussed this may not be true in actual ECAE deformation. It is suggested that choice of processing route is the more effective means of controlling texture at a high number of passes. The significance of these texture results is demonstrated by plastic anisotropy seen in texture-based yield loci. The predicted slip activities of the {110} [111] and {112} [111] slip systems are discussed.