| The results of both experimental studies and molecular dynamics simulations indicate that crystals exhibit strong size effects at the sub-micron scale: smaller is stronger. Until recently, experimental aspects of nano-scale deformation involved the effects of strain gradients, constraints of neighboring layers, grain boundaries, etc., which were key factors in observed size effects. Even without experimental constraints, many computational studies find that yield strength depends on sample size through a power relationship. Both experimental and computational results suggest that a fundamentally different plasticity mechanism might operate at the length scale of material's microstructure. In this work a brief review of some of these works is presented and compared with the results of our gold nanopillar micro-compression experiments, which were found to deform at nearly 50% of theoretical shear strength. To explain the observed size effect, we introduce our phenomenological model of hardening by dislocation starvation. |
full paper (pdf, 352 Kb)