Metalli a struttura ultrafina ottenuti mediante deformazione plastica severa

A review is presented about microstructural evolution, properties and fabrication processes of ultrafine grained or nanostructured alloys and pure metals by severe plastic deformation. Some of these properties are introduced with experimental results obtained by the authors on aluminium alloys and on carbon steels processed by Equal Channel Angular Pressing or by caliber rolling at moderate temperatures. It is highlighted that common principles exist for microstrutural evolution of alloys strained in the severe plastic deformation regime. Laboratory techniques for the synthesis of bulk nanostructured metals are currently well developed while further work is still required to develop suitable processes that can be inserted in industrial production lines. Finally, ultrafine metals feature a highly non-equilibrium structure, especially in their grain boundary regions. The resulting high reactivity accounts for the rapid diffusion, grain growth and phase transformation.