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s, i lnZ = 22–66, to investigate the effect of Z on its microstructures and mechanical properties. It was found that deformation twinning occurs when lnZ exceeds 30, and the number of twins increases at higher Z. The average twin/matrix lamellar thickness is independent methods for producing ultrafine-grained (UFG; grain size For example, both the SPD processes and the cold-rolling can eventually refine grains of pure Cu down to a few the grain size or increasing the strength [6,7]. Therefore, the in various metals and alloys by means of special plastic deformation processes, such as ball milling [8], surface mechanical attrition treatment [9,10] and cryogenic rolling [11,12]. In these processes, either high strain rates or low temperatures (or both) are applied. Very recently, we dem-onstrated that bulk NS Cu specimens with much higher * Corresponding author