Unravelling the Size‐Dependent Mechanical Properties of Nanocrystalline Face‐Centered‐Cubic Metals: From the Dislocation Point of View

The grain size dependence of strain rate sensitivity, apparent activation volume, and yield stress of nanocrystalline (NC) face‐centered‐cubic metals (FCC) are modeled based on the bow‐out model of single dislocation. It is found that the grain size limitation on the dislocation length gives rise to the grain size effects on the mechanical properties. The model gives predictions that when temperature is at or below room temperature and the strain rate is in the quasistatic range, dislocation‐mediated mechanisms play a dominant role in the plastic deformations of FCC NC metals even for the grain size of several nanometers, which is consistent with known experimental and simulation results. Based on the model, abnormal mechanical phenomena of nanostructured metals, such as the appearance of the inverse Hall–Petch relationship, the existence of the critical grain size, and its strain rate dependence, are well predicted and interpreted.