Modelling of strain hardening and microstructural evolution in equal channel angular extrusion

Strain hardening as well as crystallographic texture development is studied in polycrystalline OFHC Cu subjected to equal channel angular extrusion (ECAE) up to four passes. The experiments have been carried out at room temperature in a 90° die, following Route A processing. Texture development was followed using pole figures and hardening was measured by Vickers hardness testing. The self-consistent viscoplastic polycrystal plasticity model in its isotropic version [Acta Met. Mater. 42 (1994) 2453] was used for modelling the evolution of the texture. A previously proposed strain-hardening model [J. Eng. Mater. Techn. 124 (2002) 71], based on the dislocation cell structure of the material, was incorporated into the polycrystal model to predict the hardening behaviour. For the passage of the material in the ECAE die, the recently proposed flow line model was employed [Adv. Eng. Mater. 5 (2003) 308]. The experimental textures as well as the hardening curves are qualitatively reproduced by this modelling and an important effect of the varying strain rate within the ECAE die on hardening has been found.