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A brief overview is presented for means of severe plastic deformation during the formation of gradient structure from the viewpoint of physical mesomechanics. An analysis of the results on the impact of the means of drawing with shear on steel; severe plastic deformation by high pressure torsion on steel, titanium, and copper; and alternating bending by applying a ECAP-Conform stand on copper. It is shown that structures with different degrees of gradient form in the materials as a result of these actions.

Problem Statement (Relevance): The paper describes some features and prospective benefits of deformation by methods of drawing with shear (SD) and high pressure torsion (HPT) in a temperature range of dynamic strain aging (DSA) effect, which allow receiving a high complex of physical and mechanical properties. Objectives: The study aims to investigate and analyze features of the structure formation with the combined application of severe plastic deformation (SPD) and the DSA effect during deformation by drawing with shear and high pressure torsion, to establish patterns of the gradient structure formation. Methods Applied: 1. Computer simulation in Deform 3D software to investigate the stress-strain state on materials with various types of a crystalline lattice: copper grade M1 (FCC), Steel 10 (BCC) and titanium VT1-0 (HCP) and a further comparison with experimental results. 2. Microhardness measurement 3. Scanning and transmission electron microscopy. Originality: This research resulted in investigation of the combined effect of the DSA effect and SPD on the gradient structure formation and mechanical properties of metals with various crystalline lattices. Findings: the paper presents the results of the study of the structure formation during non-monotonous plastic deformation of the alloys (steel 10, copper and titanium) with various crystalline lattice types by SD, as well as ECAP and HPT of low-carbon steel in the temperature range of the DSA effect. Deformation mechanisms and features of the deformation behavior on a mesoscopic scale under various deformation treatment modes are analyzed. The temperature range of the DSA effect in steel 10 under ECAP and the fact of the gradient structure formation under HPT are established. Practical Relevance: The study helped to obtain data that can be used to choose the optimal deformation treatment mode with the DSA effect.

In this work, the influence of the crystallographic orientation of high-purity aluminum single crystals of grade A999 on the transformation of the initial structure as a result of exposure to shock waves at a temperature of −196°C was experimentally investigated. It was found that when the shock front propagates in the [110] direction at pressures of 40 GPa and 50 GPa, structural changes in aluminum single crystals are observed in the form of dislocation slip lines along the (111) and (110) planes. The impact of the shock front in the direction of [113] at a pressure of 50 GPa leads to coordination structural changes. It was found that a nanocrystalline structure with an average grain size of 80 nm is formed in the near-surface layers at a depth of 1–3 mm, and a subgrain structure is formed at a depth of 6–7 mm. In fact, a gradient type structure is formed. The reasons for the pronounced effect of the influence of the crystallographic orientation of high-purity aluminum single crystals on structural changes under the action of shock waves are discussed.

Special aluminum alloys appear to be promising materials for manufacture of high-strength light-alloy drill pipes (HSLADP) that can be used in areas with a severe climate and challenging geology. The effect of using light-alloy drill pipes (LADP) depends directly on the properties of the aluminum alloys from which such pipes are made. As the wells become deeper and horizontal wellbores get longer, use of LADPs becomes more relevant. Since light-alloy pipes are 2.8 times softer than steel pipes, LADPs offer the same performance as steel drill pipes of the lowest strength grade even in the case of rotary drilling. The materials from which such pipes are made have a number of unique advantages: extra light weight in the drill mud, allowing the coefficient of sliding friction between the pipe surface and the borehole wall to be reduced; high corrosion resistance in aggressive media with A high concentration of hydrogen sulfide and carbon dioxide; and high magnetic inductive capacity that allows LADPs to be used as a housing for MWD (measurement while drilling) and LWD (logging while drilling) telemetry systems during well-drilling operations. This study suggests methods for industrial production of submicrocrystalline (SMC) structure in aluminum alloys with the help of severe plastic deformation. Through the example of model aluminum-lithium alloys 1420 (Al-Mg-Li-Zr) and 1460 (Al-Сu-Li-Zr), the researchers demonstrate that SMC structure helps significantly increase resistance to wear and reduce the rate of corrosion depending on the pH value. The research team also states that severe plastic deformation methods may be used to develop highly promising technologies for manufacture of high-strength LADPs with advanced strain-stress properties for use during operations in the Arctic.

The formation of a gradient structure during the severe plastic deformation (SPD) by high-pressure torsion (HPT) of low- and medium-carbon steels under the influence of dynamic strain aging (DSA) is studied. Deformation mechanisms under various regimes of deformation processing are analyzed. The temperature ranges of the DSA effect during the ECAP processing of steel 10 and the fact of the formation of a gradient structure during the HPT processing under these conditions are established. It is shown that the deformation of carbon steels in the DSA temperature range enables controlling the structure of the deformed state.

Equal-channel angular pressing was used to process a commercial 1421 aluminum alloy at temperatures from 340 to 410 °C. An optimum ultrafine microstructure was achieved after pressing at 370 °C with an equiaxed grain size of ∼0.3–0.4 μm. Tensile testing showed this material is superplastic at 400 °C with elongations up to ∼1500%. Offsets in surface marker lines demonstrate grain boundary sliding is the dominant flow process.

Equal-channel angular (ECA) pressing is a processing procedure which subjects a material to severe plastic deformation. Tests were conducted on a commercial cast aluminum alloy to evaluate the properties associated with samples subjected to three different ECA pressing procedures. The results show that all three procedures lead to an ultrafine microstructure and each procedure is capable of producing samples which exhibit high strain rate superplasticity. Optimum superplastic properties were achieved in samples subjected to ECA pressing to a strain of ∼12. Under these conditions, the measured elongations to failure at a temperature of 673 K were 1210 and 950% at strain rates of 10−1 and 1 s−1, respectively.

Equal-channel angular (ECA) pressing has been used to introduce a very small grain size into a commercial cast Al-Mg-Li-Zr alloy. Tensile testing reveals the potential for achieving superplastic ductilities in this alloy at very -high strain rates (greater than 10-2s-1) but experiments show that this potential is realized only if a sufficiently high strain is introduced during the ECA pressing such that the microstructure is homogeneous and consists of an array of grains having large-angle grain boundaries.

Ultrafine grain sizes were introduced into samples of an Al-3 pct Mg solid solution alloy and a cast Al-Mg-Li-Zr alloy using the process of equal-channel angular (ECA) pressing. The Al-3 pct Mg alloy exhibited a grain size of ∼0.23 µm after pressing at room temperature to a strain of ∼4, but there was significant grain growth when the pressed material was heated to temperatures above ∼450 K. The Al-Mg-Li-Zr alloy exhibited a grain size of ∼1.2 µm, and the microstructure was heterogeneous after pressing to a strain of ∼4 at 673 K and homogeneous after pressing to a strain of ∼8 at 673 K with an additional strain of ∼4 at 473 K. The heterogeneous material exhibited superplastic-like flow, but the homogeneous material exhibited high-strain-rate superplasticity with an elongation of >1000 pct at 623 K at a strain rate of 10−2 s−1. It is concluded that a homogeneous microstructure is required, and therefore a high pressing strain, in order to attain high-strain-rate superplasticity (HSR SP) in ultrafine-grained materials.

Experiments were conducted to determine the age-hardening characteristics and the mechanical properties of an Al-5.5 pct Mg-2.2 pct Li-0.12 pct Zr alloy processed by equal-channel angular (ECA) pressing to give a very fine grain size of ∼1.2 µm. The results show that peak aging occurs more rapidly when the grain size is very fine, and this effect is interpreted in terms of the higher volume of precipitate-free zones in the fine-grained material. Mechanical testing demonstrates that the ECA-pressed material exhibits high strength and good ductility at room temperature compared to conventional Al alloys containing Li. Elongations of up to ∼550 pct may be achieved at an elevated temperature of 603 K in the ECA-pressed condition, thereby confirming that, in this condition, the alloy may be a suitable candidate material for use in superplastic forming operations.

Experiments were conducted on an Al5.5% Mg2.2% Li0.12% Zr alloy to investigate the feasibility of introducing an ultra-fine grain size using equal-channel angular (ECA) pressing and of retaining an ultra-fine grain size at elevated temperatures. It is shown that ECA pressing is capable of reducing the grain size from an initial value of ∼ 400 μm to a value of ∼ 1.2 μm. However, the microstructure after ECA pressing is heterogeneous, with many areas of equiaxed grains having high angle grain boundaries and some regions of subgrains with boundaries having low angles of misorientation. Unlike earlier experiments on AlMg binary alloys, it is demonstrated that the grain size of the AlMgLiZr alloy is reasonably stable up to temperatures as high as ∼ 700 K because of the presence in the matrix of a fine dispersion of β′-Al 3 Zr precipitates. Microhardness data confirm the Hall-Petch relationship for grain sizes above ∼ 2 μm produced by annealing at temperatures above ∼ 673 K, but the Hall-Petch relationship breaks down at smaller grain sizes because of variations in the volume fraction of the δ′-Al 3 Li precipitates.

A submicrometer-grained (SMG) Al−3% Mg solid solution alloy, with an initial grain size of ∼0.2 μm, was produced by intense plastic straining. Experiments show that tensile specimens of the SMG alloy exhibit high elongations to failure at low testing strain rates at the relatively low temperature of 403 K. The stress exponent is high (∼7–8) and calculations show deformation is within the region of power-law breakdown. The initial microstructure of the alloy consists of diffuse boundaries between highly deformed grains. At strain rates of ∼10−4 s−1 and lower, plastic deformation leads to dynamic recrystallization and the formation of highly nonequilibrium grain boundaries that gradually evolve into a more equilibrated configuration.

The peculiarities of a submicron-grained structure formation in a series of aluminium- and magnesium-based alloys by means of a special strain-heat treatment are examined in this paper. The unusual mechanical properties of alloys displayed in this state at room temperature as well as at enhanced temperatures are found. The nature of the plastic deformation of these materials is discussed.

Fine-grained structures were introduced in two commercial Al-based alloys (Al-1420: A1-5.5%Mg-2.2%Li-0.12%Zr; Supral: AI-6%Cu-0.4%Zr) by intense plastic straining using the Equal-Channel Angular (ECA) pressing technique. Mechanical testing was performed in the temperature range of 473–673 K and in the strain rate range of 10−4 -ls−1. Superplastic behaviour was observed, characterised by low flow stresses and very large elongation to failure. A maximum elongation of 1180% was obtained in Al-1420 at 623 K and 10−2 s−1 and 970% for Supral at 573 K and 10−2 s−1. The results are a significant improvement over earlier studies and this improvement is due to the presence of a homogeneous fine structure obtained through optimisation of the ECA pressing parameters. It is important to note that the fine microstructure in Al-1420 is thermally stable at these high testing temperatures.