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Multiple studies in recent years have proved severe plastic deformation (SPD) techniques as a very efficient way to produce nanostructured metals and alloys with significantly improved mechanical and functional properties, the latter affected by several factors, including ultrafine grains and also the atomic structure of boundaries in resulting nanomaterials. This report presents the results of complex studies of the formation of different grain boundaries (low angle and high angle ones, special and random, equilibrium and non-equilibrium with strain-distorted structure as well as with the presence of grain boundary segregations and precipitations) in nanostructured materials processed using SPD with various regimes and routes.

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Microstructural regularities of failure surfaces and low-temperature mechanical characteristics in quasistatic uniaxial tension and compression have been studied for ultra-fine grained structural states of Ti-6Al-4V ELI alloy processed by equal channel angular pressing. Values of the yield stress and uniform strain at 300, 77, and 4.2 K have been compared for structural states of the Ti-6Al-4V ELI alloy that differ in the average grain size and the morphology of α and β phases. Statistical distributions of dimple sizes on the failure surfaces have been studied for different structural states and temperatures. Исследованы особенности микроструктуры поверхностей излома и низкотемпературные механические свойства сверхмелкозернистого ELI-сплава Ti-6Al-4V, обработанного методом равноканального углового прессования, при квазистатическом одноосном растяжении и сжатии. Проведено сравнение значений предела текучести и однородной деформации, полученных при температурах 300, 77 и 4,2 К для разных структурных состояний ELI-сплава ТІ-6А1-4У с различным средним размером зерна и морфологией α- и β-фаз. Исследовано статистическое распределение размеров ямок на поверхностях излома при различных структурных состояниях и температурах.

High-resolution transmission electron microscopy and three-dimensional atom probe observations show clearly that a reverse transformation of body-centred cubic ferrite to face-centred cubic austenite occurs during severe plastic deformation of a pearlitic steel resulting in a nanocrystalline structure, something that never occurs in conventional deformation of coarse-grained iron and steels. The driving force and the mechanisms of this reverse transformation are discussed. It is shown that nanostructure and shear stresses are essential for this process, and the results confirm molecular dynamics predictions of such transformations in nanocrystalline iron.

This paper reports the results of investigation of mechanical behavior of the ultrafinegrained (UFG) Ti-6Al-4V alloy processed by equal-channel angular pressing (ECAP) and extrusion at temperatures in a range of 500−800°C. The UFG alloy reveals superplastic behavior at relatively low temperatures down to 600°C (elongation 240%). The features of microstructure change of the UFG alloy under superplastic straining conditions that contribute to additional strengthening of the alloy are shown.

During the last decade severe plastic deformation (SPD) has become a widely known method of materials processing used for fabrication of ultrafine-grained materials with attractive properties. Nowadays SPD processing is rapidly developing and is on the verge of a transition from lab-scale research to commercial production. This paper focuses on several new trends in the development of SPD techniques for effective grain refinement, including those for commercial alloys, and presents new SPD processing routes to produce bulk nanocrystalline materials.

The investigation of the backpressure effect during equal-channel angular pressing (ECAP) on formation of ultrafine-grained (UFG) structure in pure copper has revealed that the increased hydrostatic pressure can contribute to formation of a more homogeneous microstructure with finer grains. ECAP with backpressure also exerts a favorable effect on strength and ductility characteristics of the UFG material.

Nanocrystalline Ag-Cu powder compacts of identical composition have been prepared by 3 different methods: a) compaction of Ag-Cu alloy nanopowder prepared by inert gas condensation of a prealloy (IGC), b) mechanical alloying (MA) of elemental Ag and Cu powders, c) severe plastic deformation (SPID) of a course grained ingot material as well as of a compact of [GC and MA powder. The resulting microstructures have been studied as a function of annealing temperature by means of XRD and TEM in-situ. It is shown that IGC of the prealloy results in a duplex nanostructure, whereas MA and SPID lead to a metastable solid solution phase that decomposes to fine Ag and Cu on heating.