Vacancy-assisted hardening in nanostructured metals

Bulk metals deformed by severe plastic deformation have some unusual phenomenon such as hardening by low temperature annealing. Commercial purity aluminum processed by equal channel angular pressing has been used to investigate the deformation mechanism during further annealing of the severed plastic deformed materials. It has been found that vacancy-type defects induced by severe plastic deformation are responsible for some unusual phenomena, such as hardening by annealing and softening by slight deformation in nanostructured metals. It is anticipated that the effective control of vacancy-type defects during SPD and consequent annealing process will be combined to attain an optimum combination of strength and ductility in nanostructured metals.