Plastic flow anisotropy of pure zirconium after severe plastic deformation at room temperature

The present work investigates the plastic flow anisotropy of zirconium following one pass of equal-channel angular extrusion (ECAE) at room temperature in a 90o die. Samples were oriented with their strong basal pole texture either aligned with or perpendicular to the extrusion direction prior to processing, which leads to two significantly different starting textures. After ECAE, the samples were compressed to 30% along one of three sample directions. A visco-plastic self-consistent polycrystal model was used to determine the mechanisms responsible for the observed anisotropy. Using the same single-crystal material parameters, the model reasonably predicts texture evolution and the post-compression stress-strain response. We found that basal slip is crucial in reproducing the experimental results, and twinning makes an important contribution. These findings are noteworthy because basal slip is not active in zirconium at room temperature, and grain size reductions associated with ECAE are expected to suppress deformation twinning.