Synthesis of bulk nanostructured materials by repeated cold-rolling

Repeated cold-rolling with intermediate folding represents an alternative severe plastic deformation technique to produce extremely fine-grained bulk nanocrystalline materials at ambient temperature. In the present work, massive nanocrystalline samples of Ni with an average grain size less than 10 nm have been synthesized. Such small grain sizes have not been obtained for a pure fcc-metal by any other SPD technique. The main key to refine the microstructure via plastic deformation seems to be the requirement to apply a very large plastic strain but not necessarily the simultaneous application of a high pressure in the range of several GPa.