Grain refinement via formation and subdivision of microbands and thin laths structures in cold-rolled hafnium

The microstructural evolution and mechanical properties of pure hafnium subjected to cold rolling were investigated in this paper. Structural characterization indicates that slip dominated the plastic deformation and the microstructural evolution follows the sequence: original coarse grains - formation of microbands - formation of thin laths in microbands and formation of elongated grains in locally formed shear bands - the longitudinal splitting and transverse breakdown of laths to elongated segments - formation of nano-grains through further transverse breakdown of elongated segments. Hardness results indicate that strain hardening occurred during the whole rolling process, which can be attributed to dislocation activities and grain refinement effect.