Ultratough nanocrystalline copper with a narrow grain size distribution

We report a unique way of using mechanical milling/in situ consolidation at both liquid-nitrogen and room temperature to produce artifact-free nanocrystalline Cu (23 nm) with a narrow grain size distribution. This nanocrystalline Cu exhibits an extraordinarily high yield strength (770 MPa), as predicted from a Hall-Petch extrapolation, along with good ductility (comparable with similar to30% uniform tensile elongation). Possible factors leading to this excellent optimization of strength and ductility are discussed. (C) 2004 American Institute of Physics.