Tensile properties of in situ consolidated nanocrystalline Cu

We have prepared Cu powders with nanocrystalline grain sizes via ball milling at liquid nitrogen temperature. An in situ consolidation technique was used to produce fully dense nanocrystalline Cu samples centimeters in lateral dimensions and about one millimeter in thickness. We report a much improved combination of tensile strength and ductility, over the tensile properties of other nanocrystalline Cu materials documented in the literature. We also demonstrate the elevated strain rate sensitivity and strong temperature dependence of the flow stress and explain the results in terms of the thermally activated deformation mechanisms operative in the nanocrystalline grains. The nearly perfectly plastic behavior and shear localization observed are discussed and compared with the strain hardening behavior and deformation modes known for other nanocrystalline metals.