Superplasticity extensibility and deformation mechanism of a nanocrystalline copper sample

By means of the electrodeposition technique, a bulk sample of nanocrystalline (nc) copper was prepared with high purity and high density. An extreme extensibility (elongation > 5000 %) without a strain hardening effect was observed when the nc Cu sample was rolled at room temperature. A detailed study on the microstructure evolution of the nc Cu during the cold-rolling process was examined by means of X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), and thermal analysis. It was indicated that the deformation process in the tic Cu sample is dominated by the grain boundary activity rather than lattice dislocation. This phenomenon agrees well with the observed mechanical behavior of the nc Cu sample.