Ultrafine-grained microstructures evolving during severe plastic deformation

The microstructures of ultrafine-grained nanostructured materials developed by severe plastic deformation are widely varied in their grain size and gr ain-size distribution; grain boundaries and their structures; lattice defec ts, especially dislocations; point defects; and impurities. All of these fe atures can be influence by the way severe plastic deformation is applied, a nd thereby have decisive effects on the physical and mechanical properties of the material. Probably, the most important factors determining microstru cture are the imposed stress tensor, the degree and rate of strain, the tem perature of deformation, the chemical composition of the deformed material, and the type of crystal lattice, showing that in order to develop specific properties, it is crucial to understand and optimize the microstructure.