Work-hardening stages of AA1070 and AA6060 after severe plastic deformation

Based on the concept of work-hardening for fcc metals, the commercially pure aluminum AA1070 (soft annealed) and the aluminum alloy AA6060 (peak-aged) were investigated. Equal-channel angular pressing (ECAP) was used to introduce very high strains and an ultrafine-grained microstructure. Compression tests were performed in a wide range of strain rates between 10(-4) and 10(3) s(-1) subsequently. The results show that strain path and the corresponding dislocation structure are important for the post-ECAP yielding and the following hardening response. Furthermore, the precipitates of the alloy clearly constrain the interactions of dislocations in work-hardening stage III-causing lower strain rate sensitivity and retarding the process of grain refinement as well. If compared to the pure aluminum, the precipitates avoid hardening in stage V where an additional rate and temperature-dependent effect contributes-supposedly caused by the interaction of deformation-induced vacancies and dislocations.