Superplasticity extensibility and deformation mechanism of a nanocrystalline copper sample

By means of the electrodeposition technique, a bulk sample of nanocrystalli ne (nc) copper was prepared with high purity and high density. An extreme e xtensibility (elongation > 5000 %) without a strain hardening effect was ob served when the nc Cu sample was rolled at room temperature. A detailed stu dy on the microstructure evolution of the nc Cu during the cold-rolling pro cess was examined by means of X-ray diffraction (XRD) analysis, transmissio n electron microscopy (TEM), and thermal analysis. It was indicated that th e deformation process in the tic Cu sample is dominated by the grain bounda ry activity rather than lattice dislocation. This phenomenon agrees well wi th the observed mechanical behavior of the nc Cu sample.