Ultrafine-grain metals by severe plastic deformation

As a relatively simple top-down technique to produce nanomaterials in bulk, severe plastic deformation became a new way of transforming the microstructure of the material. When carried out at sufficiently low temperature, extreme large plastic deformations lead to ultrafine-grain or nearly nano-structured material. The aim of the present tutorial review is to give basic insight into the field of ultrafine-grain materials obtained by severe plastic deformation. The main features of the obtained microstructures are presented, the most important advantage of ultrafine-grain materials - an enhanced mechanical strength with respect to their coarse grained counterparts - is discussed. The operating deformation mechanisms that lead to the grain refinement are also examined. Finally, dynamic recrystallization which produces the ultrafine-grain structure is characterized and the main results of modeling efforts reproducing the grain refinement and several microstructure features are presented.