Nanocrystalline Cu-30%Zn samples were produced by high-energy ball milling at 77K and room temperature. Cryomilled flakes were further processed by ultra high-strain high-pressure torsion or room-temperature milling to produce bulk artefact-free samples. Deformation-induced grain growth and a reduction in twin probability were observed in high-pressure torsion consolidated samples. Investigations of the mechanical properties by hardness measurements and tensile tests revealed that, at grain sizes of less than about 35nm, Cu-30%Zn deviated from the classical Hall-Petch relationship and the strength of nanocrystalline Cu-30%Zn was comparable to that of nanocrystalline pure copper. High-resolution transmission electron microscopy revealed a high density of finely-spaced deformation nanotwins, formed due to the low stacking-fault energy of 14mJ/m2 and low-temperature severe plastic deformation.

Deformation Twins and Related Softening Behavior in Nanocrystalline Cu-30%Zn Alloy. H.Bahmanpour, K.M.Youssef, J.Horky, D.Setman, M.A.Atwater, M.J.Zehetbauer, R.O.Scattergood, C.C.Koch: Acta Materialia, 2012, 60[8], 3340-9