The defect structures of plastically deformed nanocrystalline material were investigated by means of high-resolution transmission electron microscopy. Samples with an average grain size of about 15nm were prepared by inert-gas condensation, and were plastically deformed by cold rolling up to a true strain of 0.32; using a strain rate of about 0.3/s. Frequent deformation twinning on the {111} planes was found, and Shockley partial dislocations were identified. Within each grain, twinning occurred only on a single set of parallel planes. This implied that only one of the 5 independent slip systems, required for general deformation of a grain, was active. It was suggested that grain rotation and grain-boundary sliding was active, together with twinning.

Deformation Twinning in Nanocrystalline Pd. H.Rösner, J.Markmann, J.Weissmüller: Philosophical Magazine Letters, 2004, 84[5], 321-34