Evaluating the paradox of strength and ductility in ultrafine-grained oxygen-free copper processed by ECAP at room temperature

Oxygen-free copper of >99.95% purity was processed by equal-channel angular pressing at room temperature (RT) for up to 24 passes and then pulled failure RT using strain rates from 10?4 10?2 s?1. The results show that the microstrain increases with lower numbers but decreases between 16 passes. Similar trends were found also dislocation density, Vickers microhardness values measured yield stresses in tensile testing. X-ray diffraction measurements showed a minor increase crystallite size high imposed processing through These demonstrate occurrence dynamic recovery highest strain. In testing rate 10?3 s?1 gave stress ~391 MPa an elongation 52% which is consistent earlier report Cu much higher not same purity.