On the Yield Stress of Bulk Nano Grained Polycrystals

抄録

In this paper we review previous analyses of the reasons for the departure from the Hall–Petch law observed in nano grained metallic polycrystals. We remind at first that the -D ^{- 1/2} scaling of the flow stress in coarse grained metallic polycrystals is not associated with planar slip and pile ups, but that it is a consequence of the building of a 3-dimensional microstructure. We show afterwards that the main reason for the specific behaviour of nano grained metallic polycrystals lies in the difference of the extent of the route followed by the material from elastic to plastic deformation, itself a consequence of the small extent of the dislocations mean free path in these structures.