Structural-scaling transitions and thermodynamic and kinetic effects in submicro-(nano-)crystalline bulk materials

Abstract

The size effects involved in the transition to a nanostructural bulk state is considered as a complex of phenomena associated with a change in material properties in response to a change in particle size and its attendant growth of grain-boundary defects in importance. Attention is focused on two fundamental problems: transition to submicro-(nano-)crystalline bulk states under severe plastic deformation and description of properties of nanocrystalline bulk materials. The key question to be resolved is whether a sharp distinction exists between the state of ordinary polycrystalline bulk materials and the state of nanostructured bulk materials. In qualitative terms, the transition to a nanostructural bulk state is related to new critical phenomena, namely structural-scaling transitions, occurring in systems with mesodefects. These transitions allow determination of the types of collective modes in defect ensembles for the characteristic solid states: quasibrittle, ductile and nanocrystalline.