Four alloys of the quaternary Co–Ti–Ta–Re system were synthesized within the compositional range of the FCC cobalt solid solution. The alloys were subjected to a two-stage heat treatment comprising homogenization at 1375 K for 100 h followed by aging at 1200 K for 24 h. After each heat-treatment stage, the alloys were examined by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), transmission electron microscopy (TEM), and electron diffraction. It was found that after homogenizing annealing at 1375 K followed by rapid water quenching accompanied by fracture of the quartz ampoule (average cooling rate ~10000 K/min), no Guinier–Preston zones formed. This is attributed to the fact that, at the selected compositions, FCC cobalt is unsaturated with respect to both tantalum and titanium. The detected nanoscale particles of the γ ′-Co₃(Ti,Ta) phase exhibited enlarged unit-cell parameters. This may indicate a high rhenium content in these particles, raising questions about the role of rhenium in their formation. It was also established that, for some compositions, nuclei of Laves phases may form already at the initial stages of decomposition of the FCC cobalt solid solution. Another factor affecting the selection of the optimum alloy composition for precipitation hardening is the presence of compositional regions prone to eutectoid decomposition at aging temperatures. Thus, the (γ_Co + γ ′-Co₃(Ti,Ta)) two-phase region appears to be the most promising for the development of new heat-resistant cobalt alloys based on the quaternary Co–Ti–Ta–Re system, whereas in regions with lower titanium content, the excessively low fraction of dispersed particles, the risk of Laves phase formation, and the presence of eutectoid regions hinder attainment of the required properties.

Most severe plastic deformation (SPD) methods have little prospect for wide industrial application, unlike asymmetric rolling, which under certain conditions may be accompanied by an SPD effect. This process is suitable for producing long products of the required shape with the desired surface quality. Moreover, asymmetric rolling has proven effective as a means of increasing technological ductility, thereby reducing the number of defects in aluminum rolled products. To confirm this effect, studies were carried out on the asymmetric deformation of D16, AMg6, and AD33 aluminum alloys. Symmetric and asymmetric rolling were performed using a unique scientific installation, namely the laboratory-scale industrial 400 asymmetric rolling mill at the Zhilyaev Laboratory of Mechanics of Gradient Nanomaterials, Nosov Magnitogorsk State Technical University. It is shown that all the alloys studied exhibit an improved combination of mechanical and technological properties when the asymmetry factor is increased from 1 to 5. In particular, the achieved level of technological ductility during asymmetric rolling makes it possible to recommend adjustments to the standard processing route for these alloys by reducing the number of rolling–annealing cycles. In addition, this can reduce material consumption factors and consequently increase productivity. A simultaneous improvement in both strength and ductility was observed when switching from symmetric to asymmetric rolling. The property level can also be controlled by increasing or decreasing the set roll speed ratio. Using D16 alloy as an example, it was shown that strength increases by 13 % at V₁/V₂ = 4 and by 11 % at V₁/V₂ = 5 compared with the standard processing route. Elongation increases markedly: by a factor of 2 relative to the initial state, by a factor of 34 at V₁/V₂ = 4, and by a factor of 41 at V₁/V₂ = 5 compared with the values obtained using the standard route.

This study addresses the need to improve methods for calculating deformation parameters in cold pilger tube rolling mills, identify the most accurate calculation approaches, improve tube dimensional accuracy, optimize energy consumption, and extend the service life of the deformation tooling used in these mills. The aim of the study was to determine the distribution function of deformation parameters in the sizing zone and to carry out a comparative analysis of methods for calculating the deformation fractionation parameter. The study involved an analysis of six industrial groove-pass designs for an HPT-32 mill, whose tooling had been used to roll industrial batches of tubes. Two groovepass designs employing a mandrel with a curved working-profile generatrix and four designs using conical mandrels were selected. It was found that the deformation function in the sizing zone decays over the section corresponding to the linear displacement of the tube per pass. Over a substantial part of this section, the deformation magnitude was shown to be considerably smaller than the diameter tolerance, which is important for optimizing the length of the sizing zone. Analysis of the accuracy of determining the deformation fractionation parameter showed that the method based on the P.K. Teterin formula makes it possible to determine this parameter more accurately than the generally accepted formula most widely used in the literature. The greater the deviation of the groove-pass profile and the mandrel working zone from a conical shape, the larger the discrepancy, which may reach 25–30 %. It was established that the P.K. Teterin formula for calculating the deformation fractionation parameter takes into account the effect of changes in metal volume within the deformation cone, thereby allowing this value to be determined with improved accuracy. The results obtained make it possible to improve the accuracy of deformation-parameter calculations, which is important for optimizing cold tube rolling processes.

A comparative study was carried out on the technological ductility during hot rolling and on the properties of rolled sheet products obtained by symmetric and asymmetric rolling of wrought, non-heat-treatable Al–Mg–Sc alloys 1545K and 1580. The study used ingots of these alloys with a cross-section of 210 × 100 mm produced on a laboratory unit. Symmetric rolling was performed to a thickness of 16 mm, after which the workpiece was cut into parts and subjected to either symmetric or asymmetric rolling with a roll-speed mismatch ratio of 1.5. Both rolling processes were carried out in the A.P. Zhilyaev Laboratory of Mechanics of Gradient Nanomaterials at Nosov Magnitogorsk State Technical University on an industrial laboratory 400 rolling mill. One of the key features of this mill is the presence of individual drives for the work rolls, which makes it possible to set different roll rotation speeds, with a maximum attainable work-roll speed ratio of V₁/V₂ = 10/1. After hot rolling, rolled sheet semi-finished products 6 mm in thickness were obtained and examined for microstructure. Metallographic analysis showed a positive effect of asymmetric hot rolling on grain refinement in both alloys. Subsequent cold symmetric rolling was used to produce thin-sheet semi-finished products 2 mm in thickness. During cold rolling, the rolling force in the first pass was evaluated, which also demonstrated a positive effect of roll-speed mismatch. Mechanical properties were studied on the thin-sheet semifinished products in the strain-hardened condition and after annealing at 330 °C for 2 h. The resulting mechanical properties indicate that the use of asymmetric hot rolling improves the mechanical performance of alloys 1580 and 1545K. The use of speed asymmetry makes it possible to reduce the number of passes in the finishing stand for these alloys, which in turn has a favorable effect on edge quality because it prevents their premature cooling during rolling.

This article addresses improvement of the mechanical properties of Al–Si alloys, in particular the complex-alloyed silumin AL25, by hot deformation. The aim of the study was to assess the effect of hot-deformation temperature and strain rate on the grain size of the aluminum-based solid-solution matrix, the size of silicon and intermetallic particles, and the amount of defects in the form of microcracks and micropores in AL25 alloy. AL25 alloy billets (composition, wt. %: 12.0 Si, 3.0 Cu, 1.0 Mg, 1.2 Ni, 0.7 Mn, 0.7 Fe, balance Al) were produced by permanent-mold casting. Microstructural analysis was performed using a Neophot-2 metallographic microscope and a Tescan Mira 3LHM scanning electron microscope. The billets were deformed by upsetting between f lat dies in an isothermal die on a hydraulic press and were tensile-tested at temperatures of 350–500 °C over a strain-rate range of 10^–4–10¹ s^–1 using an Instron universal electromechanical testing machine. To evaluate the effect of deformation on the structure and properties of the alloy, the initial billets were deformed at 400–500 °C and strain rates of 10^–4 and 10^–2 s^–1. Heat treatment was carried out according to the following schedule: quenching from 515 °C and aging at 210 °C for 10 h. It was shown that, after all deformation conditions followed by quenching and aging, the solid-solution structure was fine grained and recrystallized, with an average grain size of 7–15 μm. Recrystallization occurred during heating prior to quenching when deformation was performed at 350–480 °C, and also before reheating, as observed after deformation at 500 °C. The grain structure of the solid solution was heterogeneous throughout the alloy volume because of the nonuniform distribution of silicon particles and intermetallics. The smallest grains were observed in eutectic colonies, where the alloy exhibited a microduplex-type structure. Hot upsetting of AL25 alloy caused fragmentation of silicon particles and intermetallics. This process was accompanied by crack initiation within the particles; the cracks then widened, separating the newly formed fragments. Cracks in eutectic silicon crystals and intermetallics formed at all deformation temperatures. In primary crystals, cracks were observed only at a high strain rate of – 10¹ с^–1. Fragmentation of silicon particles and intermetallics was governed mainly by the degree of deformation. The formation of defects in the form of microcracks and micropores also depended on temperature and degree of deformation. As the degree of deformation increased, the total area occupied by defects, their average area, and their total number increased. A correlation was established between alloy structure and mechanical properties. Optimal temperature–strain-rate conditions were determined that promoted microcrack healing of and increased long-term strength.

Experimental specimens of the precipitation-hardenable nickel alloy base+10Fe–0.3Hf–0.3Zr–0.25Ta were produced by selfpropagating high-temperature synthesis, crushing of porous sintered compacts, air classification of the target fraction, hot isostatic pressing of the precursor powder, and vacuum heat treatment. The alloy exhibited a favorable combination of strength and ductility-related deformation characteristics at 20 and 800 °C (compressive strength = 1592 MPa, strain = 6.5 % at 20 °C; compressive strength = 623 MPa, strain = 32 % at 800 °C) owing to strengthening of the matrix phase by coherent, highly dispersed precipitates of the α-(Fe, Cr) phase and nanoparticles of the intermetallic topologically close-packed σ phase. Using in situ transmission electron microscopy to study solid-solution transformations during heating of a lamella directly in the microscope column, the optimum vacuum heat-treatment temperature was established as 900 °C. At this temperature, primary α-(Fe, Cr) particles give rise to highly dispersed secondary (Fe, Cr) precipitates measuring 10–80 nm and intermetallic σ-phase particles measuring 100–250 nm. Alloying with zirconium and iron preserves a high level of resistance to high-temperature oxidation at 1000 °C owing to the formation of a dense protective Al₂O₃ layer containing inclusions of the complex oxide (Hf, Zr)O₂. Oxidation follows a logarithmic law and almost completely ceases after 25 h of thermal cycling. Oxygen diffusion from the specimen surface into the metal interior proceeds along grain boundaries through conglomerates of (Hf, Zr)O₂ oxides. Despite the relatively high iron content, the oxidation resistance of the alloys remains high, amounting to 12.24 g/m² for base+5Fe–0.3Hf–0.3Zr–0.25Ta and 14.23 g/m² for base+10Fe–0.3Hf–0.3Zr–0.25Ta.

This study investigates the microstructure and mechanical properties of a refractory Ti₂NbZr complex concentrated alloy fabricated for the first time by laser-based directed energy deposition (DED-LB) from a pre-alloyed powder. The optimal processing parameters were identified; specifically, a laser power of 1600 W ensured a minimum porosity of 0.031 %. Comprehensive analysis revealed the formation of a single-phase BCC structure with a heterogeneous morphology, in which large columnar grains alternated with layers of fine equiaxed grains. The average grain size decreased with increasing specimen height. Mechanical testing demonstrated a favorable combination of strength and ductility, with a yield strength of ~810 MPa, an ultimate tensile strength of ~815 MPa, and an elongation of 16 %. A theoretical assessment of the contributions of the strengthening mechanisms showed good agreement with the experimental data. Solid-solution strengthening was found to make the dominant contribution to the alloy strength. The results confirm the potential of DED-LB for manufacturing high-quality Ti₂NbZr components with mechanical properties superior to those of counterparts produced by conventional and additive technologies.