On possible mechanisms of nanostructure evolution upon severe plastic deformation of metals and alloys

Nondislocation mechanisms of deformation-induced fragmentation of nanostructures in metals upon plastic deformation are discussed. Conditions under which the refinement of nanograins can effectively occur via deformation twinning and/or deformation-induced phase transformations of a martensitic type are considered. It is shown that for each metal system and each deformation method, there exists a limiting nanostructure with a minimum possible average size of nanocrystallites.