Plastic deformation of nanocrystalline materials

A model for the deformation of nanocrystalline materials based on grain boundary sliding and formation of mesoscopic glide planes is presented. The experimental result of decreasing hardness with decreasing grain size (inverse Hall-Fetch relationship) found in metals and intermetallics with nanometer grain sizes can be described by this model. For metallic systems a transition from dislocation dominated plastic deformation to grain boundary sliding occurs at a critical grain size when the stress required for dislocation motion/formation becomes larger than for grain boundary sliding. (C) 1997 Acta Metallurgica Inc.