Low temperature deformation detwinning-A reverse mode of twinning

The origin of the plasticity in bulk nanocrystalline metals have, to date, been attributed to the grain-boundary-mediated process, stress-induced grain coalescence, dislocation plasticity, and/or twinning. Here we report a different mechanism-detwinning, which operates at low temperatures during the tensile deformation of an electrodeposited Cu with a high density of nanosized growth twins. Both three-dimensional XRD microscopy using the Laue method with a submicron-sized polychromatic beam and high-energy XRD technique with a monochromatic beam provide the direct experimental evidences for low temperature detwinning of nanoscale twins. The synchrotron X-ray microdiffraction technique provides the direct experimental evidence for low temperature detwinning of copper nanoscale twins-a reverse twinning mechanism. We believe this deformation mechanism is distinct from the twinning activities previously reported in metals deformed at low temperatures or during thermal annealing. This finding indicates that the highly moveable nanoscale twin boundaries contribute greatly to the accommodation of plastic strains. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.