Effect of cold rolling on microstructure and mechanical properties of pure Zr

Though the resultant microstructure and mechanical properties of pure Zr after severe plastic deformation have been studied, the microstructural evolution and the variation of mechanical properties with progressive deformation of pure Zr have not been investigated in detail. Microstructure observation verified that dislocation slip dominated the plastic behaviour of pure Zr during room temperature deformation. With the increase in the rolling reduction (R-Zr) from zero to 90%, the various microstructural features, e.g. dislocation tangles, dislocation lamellas, dislocation cells or subgrain structure, and nano-crystal grains (similar to 72 nm), etc., successively occurred. Dynamic recovery played an important role on the plastic behaviour of the pure Zr with high stacking fault energy (SFE), which slowed down the work hardening rate during high strain rate rolling deformation and caused strain softening on the pre-deformed specimens during low strain rate tension deformation. The specimens annealed at 450-600 degrees C not only possessed higher ultimate tensile strength and yield strength, but exhibited higher elongation as compared with the undeformed specimen. The fracture mode of all annealed specimens was entirely dimple fracture. (c) 2012 Elsevier B.V. All rights reserved.