Modeling texture and microstructural evolution in the equal channel angular extrusion process I.J. Beyerlein , R.A. Lebensohn, C.N. Tome ´ Los Alamos National Laboratory, Los Alamos, NM 87545, USA Received 24 March 2002; received in revised form 6 June 2002 Abstract In this work, we develop a modeling framework for predicting the visco-plastic deformation, microstructural evolution (distributions of grain shape and size) and texture evolution in polycrystalline materials during the equal channel angular extrusion (ECAE) process, a discontinuous process of severe shear straining. The foundation of this framework is a visco-plastic self- consistent (VPSC) scheme. We consider a 908 die angle and simulate ECAE up to four passes for four processing routes, (A, C, B A and B C , as denoted in the literature) for an FCC polycrystalline material. We assume that the FCC single crystal has a constant critical resolved shear stress (CRSS), so that hardening by dislocation activity is suppressed, and the influence of grain shape distribution and texture as well as their interaction can be isolated. Many deformation microstructural features, such as grain size and shape distribution, texture, and geometric hardening  /softening, were highly dependent on processing route. Using a grain subdivision criterion based on grain shape, route A was the most effective, then route B A and route B C and lastly route C, the least effective for grain size refinement, in agreement with redundant strain theory. For producing refined equiaxed grains, route B C was more effective than routes B A and A. We show that grain  /grain interactions tend to weaken texture evolution and consequently geometric hardening and softening in all routes. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Severe plastic deformation; Strain path changes; Visco-plasticity; Grain size and shape distributions; Grain  /grain interactions; Grain refinement 1. Introduction Equal channel angular extrusion (ECAE) [1] is so far the only technique that can produce ultrafine-grained materials large enough for structural components. Polycrystalline materials processed by ECAE havea unique microstructure [1  /10] and remarkable mechan- ical properties: ultra-high strength and high ductility [1,2,5,10], as well as superplastic forming behavior [1,2]. The concomitant high strength and ductility observed in ECAE materials challenge our current understanding of microstructure  /property relationships of metals pro- cessed by severe plastic deformation. Development of a large strain deformation polycrystalline constitutive law will be a necessary tool for predicting the final deforma- tion microstructures and possibly modifying the process for an optimum combination of material properties. The ECAE process imposes multiple changes in strain path and large strain deformation on the sample. ECAE is a discontinuous process, involving inserting and re- inserting the sample in a die (see Fig. 1a), which contains two channels with equal cross-section, intersecting at an angle F [1]. As it is forced to pass through the die, the sample is severely deformed in shear as it changes its direction by the die angle F , typically ranging from as low as 908 to as high as 157.58 [1,10]. The sample undergoes no change in shape so the ECAE processing route can involve any number of passes through the die. As reported in the current literature (see [4] for review), the number of passes used has ranged from one to 16, utilizing one of four popular ECAE routes, labeled A, C, B A and B C [4,6,8]. The routes are distinguished by either clockwise (CW) or counterclockwise (CCW) rotations, usually about the sample’s bar axis (see Fig.  Corresponding author E-mail address: irene@lanl.gov (I.J. Beyerlein). Materials Science and Engineering A345 (2003) 122  /138 www.elsevier.com/locate/msea 0921-5093/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0921-5093(02)00457-4