Deformation and coble creep of nanocrystalline materials

Modeling of strengthening by nanocrystalline materials need consideration of dislocation interactions and sliding due to Coble creep, both of which may be acting simultaneously. Such a mechanism is considered in this paper. It is shown that a model based on using Coble creep (with a threshold stress) for finer grains and conventional Hall-Petch strengthening for larger grains, appears to be most successful in explaining experimental, results provided care is taken to incorporate into the analysis the effect of grain size distribution occurring in most specimens. A generalized expression relating yield stress to grain size is also proposed.