The work is devoted to the study of changes in the structural and physical properties of the precipitation-hardened CuCrZr alloy under the influence of low-temperature (77 K) quasihydroextrusion with various degrees of deformation at liquid nitrogen temperature with subsequent aging. Prior to quasihydroextrusion, commercial alloy samples were annealed and quenched from the premelting temperature to obtain a supersaturated solid solution of alloying elements in the copper matrix. After quasihydroextrusion, the microstructure, lattice constant, pole densities, tensile strength and yield strength, microhardness (in different cross-sections of the extrudate), and electrical conductivity of the CuCrZr alloy were studied depending on the degree of deformation by quasihydroextrusion. It is shown that the deformation degree determines the kinetics of decomposition of the supersaturated solid solution and its structure. As a result of extrusion, an anisotropic structure of the matrix and precipitates is formed, which also determines the anisotropy of material properties. Subsequent aging leads to a significant decrease in the anisotropy of properties. With an increase in the deformation degree during extrusion (before aging), a significant monotonous increase in physical and mechanical properties occurs. However, in the range of deformation degrees of 40–50%, an anomalous “jump” of all measured properties and structural parameters is observed. The study proposes a physical mechanism that explains the experimental results. The mechanism is based on the occurrence of two kinetically differently directed processes: dynamic aging and its inhibition due to an increase in the defectiveness of the material. The latter process manifests itself essentially at low temperatures. In general, low-temperature quasihydroextrusion makes it possible to obtain a complex of sufficiently high mechanical and electrical characteristics of the CuCrZr alloy at relatively low degrees of deformation for one extrusion cycle, which is facilitated by low deformation temperature.

Plastic deformation is one of the most important ways to improve metals and alloys' physical and mechanical properties. Many such treatment methods have been developed, but the opportunities provided by the temperature decreasing during deformation into the cryogenic region are being ignored. Despite the effectiveness of cryodeformation, work in this direction is practically not carried out today. There is reason to assume that the researchers are stopped by fears of the complexity of the implementation of such deformation treatment. There is a small number of published works dedicated to this direction, since, unfortunately, the following factors of cryodeformation applicability were not critically considered: the range of materials for which this type of plastic deformation provides the maximum effect, the complexity of equipment for such deformation. This paper discusses the problems of cryodeforming under all-around compression (barocryodeformation), methods, and features of its implementation. A new method of cryodeformation is proposed – cryo-upsetting under all-around compression, which, together with cryoquasihydroextrusion, significantly expands the possibilities of barocryodeformation of metals and alloys.

The new method of cryodeformation under all-around compression conditions is described. The impossibility of existing technologies to increase the efficiency of combined treatment of low-plasticity materials (in particular, the “upsetting-extrusion” method) by temperature treatment decreasing to the cryogenic region are considered. The technical possibility of such cryodeformation is discussed. The construction and operation principle of the developed device is described. The treatment efficiency of low-plasticity materials by this device on the example of technical magnesium and titanium nickelide alloy is shown. The need to clarify the formulations used to designate the methods of metals cryodeformation under conditions of all-round compression is discussed.

With the use of cryogenic deformations by rolling and quasi-hydroextrusion, as well as annealing up to 723 K, various structures, including nanometer ones, were created in ultrafine-grained (UFG) titanium alloy of the VT6 grade, and mechanical and dissipative properties were studied. The deformation regimes for the formation of a nanostructured state with a high level of strength characteristics without loss of plasticity are established. The revealed features of the temperature dependences in the range of 100…600 K of internal friction and shear modulus in the nanostructured state in comparison with the UFG state are analyzed.

The influence of barocryodeformation at –196°C on the phase transitions and the acoustic emission in titanium nickelide is studied. Barocryodeformation changes the temperature ranges and causes a two-stage character of the reverse martensite transformation with a decrease in the total heat absorption. The total number of acoustic emission signals increases and their energy decreases for the reverse phase transformation during heating of the samples subjected to barocryodeformation.

The effect of quasi-hydrostatic extrusion at liquid nitrogen temperature and room temperature on the evolution of structure and mechanical properties of iodide titanium and technically pure titanium VT1-0 obtained by severe plastic deformation under the scheme of upsetting-extrusion-drawing (iodide titanium) and screw extrusion-drawing (titanium VT1-0) has been examined. It was shown that combination of severe plastic deformation with cryogenic quasi-hydrostatic extrusion allowed to create nanocrystalline titanium of various purity with high strength and plasticity. It is established that, at approximately the same grain sizes, the strength characteristics of technically pure nanotitanium are significantly higher, and the plastic properties are lower than those of iodide nanotitanium.

The polycrystalline Ti Grade2 was subjected to combination of different methods of the severe plastic deformation, such as equal channel angular pressing, quasi hydro extrusion and rolling, and eight different structural states were produced. For each state were measured the following parameters: average grain size, microhardness (at 300 K) and mechanical characteristics in uniaxial compression at 300, 77 and 4.2 K. The concept of mutually complementary modes of plastic deformation differing in the set of active slip systems is introduced. The combination of the modes of plastic deformation was found, which gives the maximal values of the mechanical characteristics at temperatures 300, 77 and 4.2 K. It was shown that decrease of temperature of the preliminary deformation from 300 down to 77 K leads to improvement of the mechanical characteristics of the Ti Grade 2 samples in the whole studied temperature range.

When low-temperature quasihydroextrusion of metals was originated in the 1970s, it was not initially recognized that this is not simply an addition to the list of processes for deformation of metals at cryogenic temperatures (rolling, drawing, extrusion). The resulting structures and properties, as well as the distinctive implementation of this type of deformation, indicated that this was a new domain of plastic deformation which differed from the existing method in requiring two simultaneous conditions: cryogenic temperatures and isotropic compression. Each of these conditions makes its own "contribution" to forming the structure under this deformation and, therefore, to resulting properties. Until recently, the barocryodeformation process (as it is now called) was carried out only where it was invented, at the Kharkov Institute of Physics and Technology, but these products have been studied in many laboratories in Ukraine and abroad. This review of those studies is intended to draw attention to a new and promising area of materials science. Published by AIP Publishing.

The effect of various kinds of severe plastic deformation (equal-channel angular pressing and quasi-hydrostatic extrusion at 77 and 300 K) on the structural formation of precipitation-strengthened CuCrZr alloy has been studied. A combination of experimental methods has been used. Sputtering by deuterium ions was used as the tool for the layer-by-layer study of the alloy structure. The difference between the sputtering yields of the matrix (copper) and precipitates (Cr and Zr) allowed us to visualize the alloy structure to a total depth of 0.5−1 μm. The effect of severe plastic deformation on the precipitate distribution is considered. It has been shown that the main peculiarity of the microstructure is related to the high density of precipitates enriched in chromium, which completely determine the surface roughness. Their distribution is not related to the grain size. The combination of equal-channel angular pressing and quasi-hydrostatic extrusion was shown to lead to the increase in the microhardness of the CuCrZr alloy to 2300 MPa in the case of low-temperature quasi-hydrostatic extrusion (at 77 K) and to the retained high conductivity. It has been proved that the high anisotropy of precipitate shape, microhardness, and sputtering yield of the CuCrZr alloy is determined by equal-channel angular pressing.

Changes in material hardness of balls, which are used as the working body of ball-tube mills was investigated. Both new balls and balls with different operation time were examined. Hardness of not only the surface layer, but also over the entire depth was studied. These measurements were carried out to find the wear-out areas. It was found that areas with a reduced hardness, where ball material destruction occurs, are formed on the surface during operation. To determine the changes in the material properties, an ultimate strength was tested. Its values in different parts of the ball with the time change were found. It was revealed that the discontinuity surface structure is the same for all areas and the entire time interval. This indicates the absence of phase transitions of ball materials during operation. Diagnostics of the surface structure by the electron beam was conducted. This work allows to forecast the destruction rate of balls during their use and identify priorities for improving their performance.

Nanocrystalline bulk high-purity titanium samples were obtained by combined severe plastic deformation SPD, thermal treatment and quasi-hydrostatic extrusion QHE at liquid nitrogen LNT and room RT temperatures. Texture and microstructural evolution of Ti have been investigated by XRD methods. The effect of initial structural state on deformation behavior of Ti after QHE was established. QHE of ultrafine-grained samples leads to structure formation, which parameters are independent on temperature of QHE. Significant differences in QHE process are observed for pre-annealed coarse-grained samples. These differences are related to deformation mechanisms, activated during the QHE process at LNT and RT.

Changes in material hardness of balls, which are used as the working body of ball-tube mills was investigated. Both new balls and balls with different operation time were examined. Hardness of not only the surface layer, but also over the entire depth was studied. These measurements were carried out to find the wear-out areas. It was found that areas with a reduced hardness, where ball material destruction occurs, are formed on the surface during operation. To determine the changes in the material properties, an ultimate strength was tested. Its values in different parts of the ball with the time change were found. It was revealed that the discontinuity surface structure is the same for all areas and the entire time interval. This indicates the absence of phase transitions of ball materials during operation. Diagnostics of the surface structure by the electron beam was conducted. This work allows to forecast the destruction rate of balls during their use and identify priorities for improving their performance.

Attempt was made to determine the influence on the properties of the alloy VT1-0 of all-round pressure under cryogenic temperatures during the deformation of the alloy and in the absence of deformation. It was shown that the hardening of the material is found only in that part of the workpiece, which experienced a deformation, that is, the fact of staying alloy under hydrostatic compression does not lead to a strengthening of this material. At the same time, measurements of acoustic emission show that in the near-surface layers the forces of hydrostatic compression and in the absence of deformation causes some changes in the structure, which cause an increase in energy and (to a lesser extent) the median frequency of AE signals, possible explanation is offered.

Effect of quasi-hydrostatic extrusion at liquid nitrogen (77 K) and room (300 K) temperatures on the microhardness in high-strength CuCrZr alloy has been investigated. It is shown that the combination of equalchannel angular compression (ECAP) and quasi-hydrostatic extrusion (QHE) allows raising microhardness of CuCrZr alloy especially in the case of the low-temperature (77 K) QHE treatment.

Influence of deformation at 25% under uniform compression at pressure of 22 and 16.5 kbar at 77 K and 12 and 8 kbar at 300 K by using quasihydroextrusion with counterpressure (QHEC) and without counterpressure (QHE) on physical-mechanical properties of titanium VT1-0 in the range of 77...800 K was investigated. It was shown, that two-stage character of dependence mechanical properties versus temperature in initial state (temperature-dependent in the range of 77...600 K and athermal in the range of 600...800 K) after deformation QHE and QHEP changed to one-stage and temperature-dependent character in the entire temperature range. It was shown that deformation under uniform pressure result in increase of strength in the range of 77...800 K and decrease the stacking fault energy of titanium. That is an addition factor of hardening besides increasing the density of deformation defects. It was found that uniform compression realized under higher pressures leads to less hardening and less accumulation of deformation defects. This associated with activation of recovery processes.

The mechanical characteristics and parameters of acoustic emission have been measured by the indentation of a commercial VT1-0 titanium alloy subjected to barocryodeformation at 77 K. The correlation between the acoustic parameters and microhardness has been revealed.

The hydrogen content, mechanical characteristics, and acoustic emission parameters of VT1-0 commercial titanium alloy subjected to barocryodeformation are measured at 300 and 77 K and at 77 K with counterpressure. A correlation between the acoustic parameters and the hydrogen content is found under all barocryodeformation conditions.