QUASI-NANOCRYSTALLINE MATERIALS

Quasi-nanocrystalline materials (nanostructured polycrystals with quas i-periodic grain boundaries) are defined as new-types of nanostructure d materials. The specific role of quasi-periodic boundaries in plastic deformation in nanostructured polycrystals is theoretically examined. It is shown that quasi-periodic tilt boundaries in nanostructured pol ycrystals are capable of effectively contributing to (experimentally o bserved) deviations of the yield stress dependence on the grain size f rom the standard Hall-Fetch dependence.