At JSC «Uralelectromed», selenium-containing raw materials and industrial products are processed, resulting in solutions containing a mixture of mercury with concentrations as follows (g/dm³): 157–210 Se; 0.004–0.02 Hg; 0.15–0.20 Te; 2–3 As; 0.15–0.20 Sb; and 45–50 S. To produce branded selenium, the mercury concentration in the solution must be kept below 0.001 g/dm³. Various methods, such ashydrometallurgical and electrochemical processes, are known for mercury purification from solutions. JSC «Uralelectromed» has selected sorption technology for mercury removal using the weak-base macroporous anionite Lewatit MP-68 (Germany), which allows for control over the degree of solution purification. In pursuit of import substitution for the Western European sorbent Lewatit MP-68, we investigated several pre-selected industrial sorbents for extracting mercury anionic complexes produced in Russia (AM-2B, AN-31, AV 17-8, VP-3Ap), China (Seplite MA 940 and LSC 710), and India (Tulsion CH-95 and CH-97). Initially, in static mode, we determined the distribution coefficient (C_d), the degree of element extraction (ε), the static exchange capacity of the resins (SEC, g/dm³), and the mercury/selenium separation coefficient (D_Hg/Se) which led to the selection of the best samples: AV 17-8, Seplite MA 940, AM-2B, and CH-97, with SEC values of 0.95–0.97 g/dm³ (SEC = 0.98 g/dm³ of resin Lewatit MP-68). Subsequently, in dynamic mode, we ranked the ionites by decreasing dynamic exchange capacity (DEC / TDEC): AV 17-8 ≥ Lewatit MP-68 > AM-2B > Seplite MA 940 > Tulsion CH-97. Resins AV 17-8, Seplite MA 940, and AM-2B demonstrated similar dynamic sorption characteristics; under comparable conditions, mercury breakthrough occurred after processing at least 950 specific volumes of the initial solution. In contrast, with Lewatit MP-68 ionite, mercury breakthrough occurred after no more than 750 specific volumes, indicating the need to increase the number of sorption steps in the solution purification cascade. Considering the totality of ion-exchange properties, for further industrial testing, it is recommended to use the domestically produced resin AV 17-8 instead of the foreign sorbent Lewatit MP-68 in the sorption purification process of selenic acid to remove mercury, thereby ensuring the production of branded selenium.

This study focuses on developing a heterophase process for synthesizing rare-earth zirconates, specifically R₂Zr₂O₇ /R₂O₃·2ZrO₂ (R = La, Sm, Gd, Dy). We investigated the sorption properties of low-hydrated zirconium hydroxide, a precursor for complex-oxide phases, towards rare-earth elements' ions (La, Sm, Gd, Dy). The results indicate that sorption by low-hydrated zirconium hydroxide is a multifaceted process, involving the incorporation of rare-earth cations into the pores of low-hydrated hydroxide and ion exchange. The paper details the synthesis of R₂Zr₂O₇ /R₂O₃·2ZrO₂ (R = La, Sm, Gd, Dy), considering both «light» and «heavy» elements. The process process involves the interaction between Zr(OH)_3÷1O_0.5÷1.5·(1.6÷2.6)H₂O, low-hydrated zirconium hydroxide, and an aqueous solution of rare-earth acetate (С(La³⁺) = 0.155 mol/l, С(Sm³⁺) = 0.136 mol/l, С(Gd³⁺) = 0.141 mol/l, С(Dy³⁺) = 0.120 mol/l) followed by heat treatment. The resulting phases and their thermolysis products were analyzed using differential thermal analysis and X-ray phase analysis. Single-phase rare-earth zirconates R₂Zr₂O₇ (R = La, Sm, Gd) and the Dy₂O₃·2ZrO₂ solid solution were only obtained at 800 °С. The lattice parameters are calculated for each phase. Lanthanum, samarium, and gadolinium zirconates exibited a cubic pyrochlore structure (Fd3^–m), while dysprosium displayed a fluorite structure (Fm3^–m). The average particle size of all zirconates was 1.14 ± 0.02 μm.

Employing centrifugal self-propagating high-temperature synthesis (SHS) metallurgy, complemented by advanced metallurgical processes such as vacuum induction melting (VIM) and vacuum arc remelting (VAR), yielded the alloy formulation denoted as base–2.5Mo–1.5Re–1.5Ta–0.2Ti. This study investigates the effects of various technological modes and additional metallurgical treatments on the alloy's impurity and non-metallic inclusion content, structural characteristics, mechanical behavior under compression, and its oxidation mechanisms and kinetics when exposed to temperatures of 1150 °C for 30 h. With increasing centrifugal acceleration, the proportion of non-metallic inclusions (number of points) drops from 5 to 1–2 points. The best combination mechanical properties, including σ_ucs = 1640 ± 20 MPa, σ_ys = 1518 ± 10 MPa, and residual deformation were observed in alloys processed under conditions of increased gravitational force (g = 50). Within a centrifugal force range of g = 20÷300, the composition of the synthesis products aligned with the theoretical expectations. The total content of impurities is 0.15 ± 0.02 %, with a decrease in gas impurities–oxygen and nitrogen levels reduced to 0.018 % and 0.0011 %, respectively. The structural analysis of the alloys revealed the presence of globular and streaked inclusions of a chromium-based solid solution embedded within the matrix. Inclusions with thickness of 2–8 μm are present in the intergranular space: (Cr)_Ni,Mo,Co, (Cr)_Mo,Re and (Cr)_Re,Mo. The formation of the Ni(Al,Ti) phase at grain boundaries was identified, contributing to an enhancement in plastic resistance and overall strength of the alloy. Oxidation mechanisms varied across different processing modes, with the size of structural components significantly influencing oxidation kinetics. The weight gain observed in SHS samples was 70 ± 10 g/m² with oxidation predominantly occurring along the NiAl interphase boundaries and penetrating into the depth of the sample. TEM facilitated the identification of phases enriched with Ti microadditions, reducing the levels of dissolved nitrogen and oxygen within the intermetallic phase to a combined weight percentage (Σ_O,N) of 0.0223 wt.%.

The identification of structural components in the AM4.5Kd + 0.2 wt.% La alloy, subjected to quenching at different temperatures (535–605 °C) and artificial aging at 155 °C for 4 h, was conducted through electron microscopy and XRD. An increase in the quenching temperature from 535 to 605 °C promotes the enlargement of structural components, including the α-solid solution, various aluminides, and eutectics. We observed that the base metal is not homogeneous in its chemical composition, consisting of two types of solid solutions: α₁ and α₂. The Cu and Mn solubility in the α₂-solid solution is higher than in the α₁-solid solution. As the quenching temperature increases to t_q = 605 °C, the copper content in the α₁-solid solution decreases. In contrast, the copper content in the α₂-solid solution follows a curve with two maxima at 545 °С (4.5 at.%) and 585 °С (8.7 at.%). The Mn content in the α₁-solid solution decreases sharply to the 545 °С quenching temperature and remains relatively constant up to t_q = 605 °С (0.2 at.%). The Mn content in the α₂-solid solution follows a curve with its maximum at t_q = 545 °С (4.3 at.% Mn). Subsequent temperature rise results in a sharp drop in Mn content from 1.0 at.% at t = 565 °С to 0.3 at.% at 605 °С. Hence, the max solubility of Cu and Mn in the α2-solid solution occurs at 545 °C. At 585 °С, only an elevated Cu content (~8.7 at.%) was observed. Aluminides of alloying elements with different stoichiometries crystallize at different quenching temperatures, with complex Al_xTi_yLa_zCu_vCd_w and Al_xCu_yMn_zCd_v alloyed aluminides being most commonly found. ncreasing the quenching temperature to 535–545 °С results in higher hardness of the AM4.5Kd + 0.2 wt.% of La alloy, reaching 98–104 HB, with subsequent decrease to 60 HB as the quenching temperature reaches 605 °С. The hardness of the unhardened alloy is 60 HB. The optimal quenching temperature for the AM4.5Kd + 0.2 wt.% of La alloy is in the range of 535–545 °С. This temperature corresponds to the highest hardness of the alloy and the microhardness of the aluminide.

This research explores the potential to enhance the copper solubility limit in high-entropy alloys (HEAs) within the CoCrCuFeNi system by increasing the nickel content twofold and applying additional heat treatment. The CoCrCu_xFeNi₂ HEAs were synthesized through mechanical alloying of elemental powders followed by hot pressing. The study investigated the microstructure and phase composition of CoCrCu_xFeNi₂ HEAs in relation to varying copper concentrations (x = 0; 0.25; 0.5; 0.75; 1.0). The evaluation of the alloy matrix's chemical composition, which is based on the FCC solid solution, enabled the determination of copper solubility. It was found that doubling the nickel content, relative to the equiatomic ratio, facilitated the formation of HEAs with a homogenous FCC structure for copper concentrations up to x ≤ 0.75. Further heat treatment of these HEAs resulted in an enhanced copper solubility of up to 17.5 at.%. The mechanical and tribological properties of CoCrCuxFeNi_y HEAs were also assessed, revealing significant improvements in tensile strength (ranging from 910 to 1045 MPa) and hardness (285–395 HV) for the CoCrCu_xFeNi₂ alloys. Despite the increased copper solubility limit, the heat treatment process caused a decline in mechanical properties by 35–50 %, attributed to grain size enlargement to 5.5 μm. The CoCrCu_0.75FeNi₂ and CoCrCuFeNi₂ alloys exhibited the lowest wear rates when tested against Al₂O₃ counterbody, with wear rates of 1,58·10^–5 and 1,48·10^–5 mm³/(N·m), respectively.

We fabricate samples of PR-03N18K9M5TYu steel (equivalent to ChS4) using selective laser melting (SLM) in a nitrogen atmosphere. Our research focused on the influence of hot isostatic pressing (HIP) combined with heat treatment (HT), specifically hardening and aging, on the steel's structure and its physical and mechanical properties (σ_ucs, σ_ys, δ, ψ). Through tensile testing, we evaluated the impact of post-processing treatments (HIP followed by HT) on the material's strength. We also assessed how different post-processing protocols affected residual porosity. Our findings indicate that samples exhibiting the highest strength and plastic properties correspond to those with the least structural defects and minimal residual porosity. In-depth microstructural analysis revealed that the optimal structure–a fine-grained, homogeneous configuration–is achieved via the combined application of SLM, HIP, and subsequent HT. The improvement in mechanical properties can be primarily attributed to the dispersed hardening effect, which is a consequence of the precipitation of the superfluous Ni₃Ti phase. Fractographic examination revealed that the post-processing leads to a ductile and dimple fracture, occurring through mechanisms of shearing and detachment, giving rise to mixed-type fractures. The samples that displayed superior mechanical properties were characterized by a homogenous ductile intergranular fracture surface with clear evidence of plastic deformation. We measured the hardness (Н), modulus of elasticity (Е), and elastic recovery via indentation methods. The post-processing treatments notably enhanced material hardness and elastic modulus, with an increase from H = 4.6 GPa and E = 194 GPa in the sample post-HIP to H = 8.5 GPa and E = 256 GPa following HIP coupled with hardening and aging.

We investigated the microstructure of the Zr–2.5%Nb zirconium alloy after subjecting it to equal-channel angular pressing (ECAP) and found that ECAP at 300 °C increases the strength by 140 to 180 %. Notably, unlike other studies, our alloy did not show complete dissolution of niobium particles, which may be due to the reduced diffusion rates at the lower deformation temperature of 300 °C. Pre-treatment involving quenching before severe plastic deformation was also studied, which developed a lamellar structure introducing additional boundaries that facilitated grain refinement during subsequent ECAP. The strength of the alloy was further enhanced by solid-solution hardening, achieved through the complete dissolution of the Nb particles into the matrix post-quenching. This process resulted in a 2.3-fold increase in yield strength after quenching plus ECAP compared to the initial coarse-grained state.