Diminishing of work hardening in electroformed polycrystalline copper with nano-sized and uf-sized twins

The diminishing of strain hardening effect has been an important issue in understanding the special deformation mechanism in the nano- and ultrafine- (uf-)grained materials. The deformation of an electroformed polycrystalline pure copper with both nano- and uf-sized twins was performed by uniaxial tension. Strain hardening rate was studied using the Kocks–Mecking plot approach. Microstructure evolutions of the two-scale sized twins at different strain conditions were observed and compared by means of transmission electron microscopy. A link between the abnormal hardening rate and the deformation mode inside nano- and uf-sized twins was established, and the diminishing of the hardening rate is attributed to the enhanced creep tendency and premature recovery of the special microstructures.