Approach to nanostructured solids through the studies of submicron grained polycrystals

Using the recent results of experimental studies of the structure and properties of submicron-grained (SMG) materials prepared by severe plastic deformation, a structural model is proposed. The model is based on the concept of non-equilibrium grain boundaries containing disordered dislocation networks and junction disclinations, which induce long-range stress fields. The existence of the defects at grain boundaries leads to an excess energy, enhanced free volume, and also to the formation of elastically distorted layers near grain boundaries with changed crystal lattice spacings. This model is considered as an approach to understanding the nature of nanostructured materials and their unusual properties.