| This overview outlines the current state of the nanotwinned structures studies in metallic nanomaterials. The various processes of twin generation, such as the pulse electrodeposition technique, magnetron sputtering and different variants of severe plastic deformation (equal channel angular pressing, high pressure torsion, accumulative roll bonding, and surface mechanical grinding/rolling treatment, etc.), are described. The structural characterization of the growth/deformation twins by transmission electron microscopy methods, including high-resolution one, is discussed. Special attention is given to a surface mechanical grinding/rolling treatment for the gradient structure formation with a high content of low-angle twinned boundaries. The influence of nanotwinned structure on the nanomaterials strength, ductility, fatigue properties, electrical conductivity, especially under extreme conditions (such as high temperatures, irradiation and corrosion actions) is discussed in details. A significant increase of these properties as compared with conventional nanomaterials is underlined. In many cases, the nanomaterials with the nanotwinned and gradient structure remain tolerant to the various extreme conditions, such as high temperature heating, irradiation, deformation and corrosion actions. Some poorly researched aspects are also put into considerations. |
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