The stress–strain response of nanocrystalline metals: A quantized crystal plasticity approach

Abstract This paper develops a finite element-based model with quantized crystal plasticity (QCP) to study distinctive features of nanocrystalline (nc) metal behavior, including an enhanced flow stress, extended plastic transition strain and propensity for strain localization . The QCP feature is motivated by molecular dynamics simulations of dislocation loop propagation across nc grains, showing that the grain-averaged plastic strain jumps by discrete amounts. Further, a simple geometric analysis suggests that the magnitude of the jumps is ∼1/ grain size , thereby incorporating a grain size effect. QCP simulations of 1000-grain polycrystals can reproduce the unique experimental stress–strain features of nc metals, but only if the probability density distribution for a slip event increases abruptly at a threshold stress ∼1/ grain size . Possible explanations for such a unique signature are discussed in terms of dislocation loop expansion conditions that become important in the nc limit.