Strength and plasticity of nanocrystalline materials and nanosized crystals

The effect of grain boundaries and the crystal surface on the deformation and strength properties of nanocrystalline and nanosized materials, primarily metals, is reviewed. Basic experimental facts about the mechanical behavior of nanocrystal materials are presented and the observed findings are theoretically analyzed using equations of dislocation kinetics that take the properties of grain boundaries into account as sources, sinks, and dislocation barriers. Using a similar approach, size effects in the plastic deformation of micro- and nanocrystals are discussed by considering the crystal surface as a primary source of and sink for dislocations.