Grain Size and Additive Technologies Effects on Mechanical Properties of Alloys

Dear Colleagues,

Since the 1990s, methods for obtaining polycrystalline materials with a submicron grain size (grain diameter less than 1 micron) have been intensively developed and studied. Researchers’ and practitioners’ interest in such so-called ultra-fine-grained (UFG) or nanocrystalline materials is due to their unique physical and mechanical properties, which differ significantly from the corresponding properties of coarse-grained polycrystals. Nano- and sub-microcrystalline states in structural materials open up unique opportunities for obtaining a new level of mechanical properties: super-strength at a sufficiently high level of plasticity, hardness, low-temperature and high-speed superplasticity, low- and multi-cycle fatigue, and wear resistance. Although the mechanisms that lead to the achievement of new properties in UFG materials are still the subject of fundamental research, products made of these materials have long appeared in various fields of industry. Currently, such materials are widely used in the field of operating temperatures for parts of aviation and space equipment, the chemical industry, engineering equipment, medical implants, etc.

UFG and nanostructures can be obtained using methods such as severe plastic deformation (SPD). SPD processes are modern and developing methods of processing materials by pressure, which allow the formation of ultra-fine-grained, sub-micro- and nanocrystalline structures in bulk work pies. The most promising methods for creating bulk sub-microcrystalline materials are severe plastic deformation methods such as equal-channel angular pressing (ECAP), torsion under high pressure, comprehensive pressing, as well as methods that combine SPD with various heat treatment modes. The sub-microcrystalline structure of metals formed by such methods, in addition to the small grain size, are characterized by the presence of a large number of microdefects (dislocations, disclinations, twins, micropores, grain boundaries). Such a defective structure, combined with a small grain size, can adjust the development of strain in sub-microcrystalline materials compared to coarse-grained polycrystals. The prospect of using sub-microcrystalline materials with such an internal structure as structural materials establishes the importance of comprehensively studying the laws of their deformation behavior in a wide range of strain rates.

Prof. Dr. S. V. Razorenov
Guest Editor

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• ultra-fine-grained materials
• mechanical properties
• methods of manufacturing and diagnostics
• strain rate