Dear Colleagues,

Plenty of effort has been devoted to targeting structural materials with optimized mechanical properties, especially in the fields of civil, medical, transportation, piping, aerospace, and energy engineering. Metallic material strength and ductility are two of the most important mechanical properties to be considered when designing these materials to be used for structural purposes.

Important scientific research results and technological achievements have been obtained to produce metallic materials with a high strength and high ductility at the same time.

To obtain materials with a high strength and high ductility, significant changes of the microstructure are mandatory. In this respect, a drastic reduction of the metallic alloy grain size, possibly down to a nanoscale level, was shown to possess a good combination of high stress and high ductility, without sacrificing their specific strength.

Based on this, in the past three decades, many methods have been introduced to produce ultra-fine grain (UFG) and even nano-structured (NS) metallic materials and alloys. All of the different proposed and characterized methods can be classified into two major approaches—bottom-up and top-down. In the bottom-up approach, the refining processes start from powdered materials, that is, the metal constituents, and nano-particulate or nano-size powdered metallic materials are bonded and blended together to form NS bulk solids. In the top-down approach, the refining processes start from bulk conventional grain metallic materials that are effectively refined by heavily imposed shear strain to ultimately form UFG, and even NS metallic materials and alloys.

Scope of the present Issue is to promote a collection of the latest research works and results on both the severe plastic deformation (SPD) techniques and approaches: bottom-up and top-down. This Issue aims at providing an overview of the state of the art of SPD techniques and achievements for different metallic materials and alloys.

Prof. Dr. Marcello Cabibbo
Guest Editor

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• severe plastic deformation (SPD)
• ultra-fine grain (UFG)
• nano-structured (NS)
• metallic materials and alloys
• top-down approach
• bottom-up approach
• equal-channel angular pressing (ECAP)
• hot-pressure torsion (HPT)