Yield strength in nanocrystalline Cu during high strain rate deformation

Molecular dynamics simulations are used to study the yield strength of thermally annealed nanocrystalline Cu samples. For strain rates of 1 × 10¹⁰ and 1 × 10⁹ s^-1, the observed yield strength scales with the fractional number of grain boundary (GB) atoms. This observation suggests a new scaling behavior for the onset of plasticity in nanocrystalline materials, controlled not by the grain size alone, but by a combination of both grain size and degree of GB relaxation, as measured by the GB volume.