Russian Journal of Non-Ferrous Metals最新文献

Ti25Ta alloy has shown to have the best combination of properties for biomedical applications in comparison to the widely used Ti6Al4V alloy. However, the main disadvantage is its poor wear resistance, thus, to overcome this disadvantage the addition of boron is studied in this work. To reach our objective, Ti25TaxB alloys were obtained by mechanical milling. Three different quantities of B were added 2, 4 and 6 at %. Powders were milled during 24 h under dry conditions. Then, milled powders were uniaxial pressed at 400 MPa. Green compacts were sintered at 1260°C during 1 h under argon atmosphere. Microstructure was observed by SEM and X-ray diffraction. Results shows that addition of boron improves the compaction behavior. On the contrary, during sintering, addition of boron reduces the densification because of the in-situ TiB formation. Sintered compacts have around 20 vol % of pores. The microstructure of sintered compacts is composed of three different phases; β-Ti, α'-Ti and TiB. The microhardness of the sample with 2 at % of boron is improved 50% with respect to the one measured for the Ti25Ta alloy. It is concluded that conventional sintering allows obtaining porous compacts with high hardness that could be used for biomedical applications.

This review presents a detailed study on the fabrication of aluminium matrix composites (AMCs) using the stir-casting technique and the associated processing challenges. Owing to their low density, high specific strength, good wear resistance, and thermal stability, AMCs have attracted significant interest from both researchers and industrial sectors. Among the various fabrication routes, stir casting is widely preferred due to its simplicity, cost-effectiveness, and suitability for large-scale production. However, the process is constrained by inherent differences in the physical and mechanical properties of the aluminium matrix and the reinforcement materials, such as density mismatch, melting temperature variation, wettability, strength, and plastic deformation behavior. These factors strongly influence particle distribution, interfacial bonding, and overall composite performance. The review critically examines these challenges and highlights key considerations for improving the quality and reliability of stir-cast aluminium matrix composites.

A significant number of end-of-life computer central processing units are annually discarded, with many printed circuit boards (PCBs) containing valuable metals such as Au and Ni. This study focuses on a “continuous leaching” system and introduces an innovative method. It utilizes ammonia leaching and acid leaching sequentially to process spent lithium cobalt oxide (LCO) powder (referred to as LCO powder). The resulting leachate is then utilized as the cobalt source for a subsequent continuous leaching process to directly synthesize the [Co(NH₃)₆]³⁺ complex. Finally, the [Co(NH₃)₆]³⁺-thiosulfate system is used for gold leaching from waste PCBs. Experimental results indicate that optimal conditions for ammonia leaching–2.5 mol/L (NH₄)₂SO₃, 0.5 mol/L NH₃·H₂O, 0.5 mol/L (NH₄)₂CO₃, 80°C temperature, 100 : 1 mL/g liquid-to-solid ratio, and 10-h leaching time–yield leaching efficiencies of 84.14 and 87.69% for Co and Li, respectively. For acid leaching, optimal conditions include 0.5 mol/L H₂SO₄, 2% H₂O₂, 80°C temperature, 100 : 3 mL/g liquid-to-solid ratio, and 2-h leaching time, resulting in leaching efficiencies of 95.29 and 70.69% for Co and Li, respectively. The leachate from acid leaching is then used to synthesize the [Co(NH₃)₆]³⁺ complex, followed by employing the [Co(NH₃)₆]³⁺-thiosulfate system for gold leaching, achieving a gold leaching efficiency of 95.53% under optimal conditions. This study utilizes spent LCO powder to produce the [Co(NH₃)₆]³⁺ complex instead of directly using [Co(NH₃)₆]³⁺ salts (e.g., [Co(NH₃)₆]Cl₃), resulting in a significant cost reduction, decreased reagent consumption, and showcasing two key innovations: “synergistic extraction” and “continuous leaching”.

The work investigated the effect of alloying with boron of alloys of the system (Fe_0.25Co_0.25Ni_0.25Cr_0.125V_0.125)_{100 – x}B_x (at %), where x = 0–9 on microstructure and mechanical properties during crystallization with cooling rates of 10³–10⁴ K/s. It has been established that an increase in the boron content leads to an increase in the volume fraction of the eutectic in the structure of the alloys. The structure of the alloys with increasing boron content changes from a single-phase structure of a multicomponent solid solution with an fcc lattice to a typical hypoeutectic structure – dendrites of a solid solution surrounded by a eutectic consisting of a solid solution and boride Me₃B₂. Using X-ray diffraction and micro-X-ray spectral analysis methods, it was established that an increase in the boron content leads to a depletion of the solid solution in vanadium and chromium, which is due to their high content in the boride and an increase in its volume fraction in the structure. Increasing the boron content from 0 to 9 at % leads to an increase in the yield strength of alloys from 236 to 500 MPa, tensile strength from 514 to 798 MPa and a decrease in relative elongation from 28.1 to 3.2%. It has been shown that alloys with a boron content of up to 5 at % can be subjected to cold deformation, which leads to a significant increase in the yield strength to values exceeding 1 GPa.

The paper investigates the possibility of spontaneous infiltration of molten copper and bronze BrAZh 9-4 into porous TiC and TiC-graphite frameworks obtained by self-propagating high-temperature synthesis (SHS) in open air. The features of interphase interaction of copper and bronze melts with a temperature of 1200°C with hotter TiC and graphite frameworks after SHS (>2500°C) have been studied. The density of the obtained TiC–BrAZh and TiC–C(graphite)–BrAZh composites is 6.18 and 5.10 g/cm³, respectively. It was established that infiltration and wetting of copper and bronze melts is accompanied by partial dissolution of titanium in the melt, which indicates the reactive nature of the interaction. Intensive infiltration limits the SHS process of TiC, leaving part of the carbon in a free form. Titanium dissolved in copper precipitates on the surface of TiC and graphite particles, forming a dense crust of non-stoichiometric TiC_x around these particles. Tribological studies have shown that the addition of graphite to the TiC–BrAZh composite reduces hardness by 2.7 times, elasticity by 2.2 times, and yield strength by 1.7 times. However, it increases wear resistance by 1.5 times and reduces the instability of the friction coefficient by 0.1 with the same level of its average value.

Magnesium alloys are in spotlight of research for lightweight tribological applications. However, their low resistance to wear and unstable frictional response limits their usage. This study systematically examined the wear characteristics of 2 wt % lanthanum oxide reinforced AZ31 magnesium matrix composites developed by stir-squeeze casting. A Taguchi-based statistical framework was utilized to optimize the effects of tribological parameters (applied load, sliding speed, and sliding distance) on wear rate and coefficient of friction of the composite. Optical microscope, scanning electron microscope, energy-dispersive spectroscope, and X-ray diffraction were deployed to observe the morphological features. Characterization confirm that the lanthanum oxide was evenly dispersed, the phase was stable, and the particles were well-bonded to the matrix. Statistical analyses revealed that the applied load was the primary factor influencing both wear and friction, succeeded by sliding speed and sliding distance. Multi-objective desirability optimization produced ideal wear conditions at a 15 N, 0.5 m/s, and 1500 m wear parametric conditions. This resulted in a predicted wear rate of 0.0046 mm³/m and a coefficient of friction of 0.325, both of which were confirmed through experiments with deviations of 2–5%. Analysis of the worn surface showed a change from severe abrasive-adhesive wear to mild abrasive-oxidative wear when conditions were optimized. These findings demonstrate that lanthanum oxide reinforcement improves the dry sliding tribological response of AZ31 magnesium composites, indicating their potential for lightweight structural components where sliding contact and wear resistance are required.

The range of applications for metal matrix composite materials is expanding daily due to their outstanding characteristics. Copper matrix metal matrix composites are among the first to come to mind for metal matrix composites (MMCs). The areas of use of copper alloys and copper matrix composites are diverse thanks to their mechanical, electrical, corrosion, and abrasion resistance. With the production of composites with a bimetallic matrix, it is possible to produce twice as successful composites with both ceramic reinforcement and bimetallic matrix reinforcement. This study investigated the microstructural, mechanical, and tribomechanical properties of 10% WC reinforced copper matrix composites with varying Ti element addition. The WC-added copper-titanium matrix composites’ relative densities were higher than 92%. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS), SEM elemental mapping (SEM-mapping) analyses were performed on the composites, and the phases and grain structures developed during heat treatment were examined. In addition, electrical conductivity measurements showed a significant decrease in the conductivity of WC-doped Cu matrix composites due to the increase in the Ti ratio. Dry sliding wear tests were conducted using a ball-on-disk configuration. The Ti-reinforced Cu matrix composite containing 8% Ti by volume has a hardness of 154.5 HV and wear rate of 4.9 × 10^–5 mm³/(N m), exhibiting approximately 1.12 times higher hardness and 12 times greater abrasion resistance compared to the composite without Ti addition. Considering the widespread use of copper matrix composites in sectors such as automotive, aircraft, etc., WC and titanium-doped copper matrix composites are promising thanks to their superior properties.

In the present work, using the three‑phase (α₂ + β + γ) alloy TNM–B1 (Ti–43.5Al–4Nb–1Mo–0.1B) as an example, a comparative study was carried out of the effect of the heterogeneous structure formed during the cellular reaction on the mechanical behavior and structural evolution during hot deformation in the upper part of the (α₂ + β + γ) phase field at T = 1050°C. The alloy in the as‑cast condition with a fine lamellar structure (interlamellar spacing λ ~ 100 nm) and after preliminary heat treatment (HT) (oil quench from the (α + β) region at T = 1290°C) were subjected to isothermal uniaxial compression at an initial strain rate of 0.001 s^–1 to ε = 70%. The as‑cast alloy exhibited the typical microstructural evolution of cast alloys, characterized by preferential localization of plastic deformation at colony boundaries, leading to the development of dynamic recrystallization/spheroidization. In the pre‑heat‑treated condition, a cellular reaction was found to occur already upon heating to the deformation temperature (T = 1050°C); prior to deformation a heterogeneous microstructure had formed, consisting of nano‑lamellar and differently oriented coarse lamellar colonies (λ ~ 10 nm and 0.3–1.0 µm, respectively) in a ~70/30 ratio. The study showed that formation of this heterogeneous structure leads to a reduction in peak stresses (from 350 MPa for the as‑cast condition to 220 MPa after HT) and to a more extended steady‑state flow stage, where stresses decreased from 280 MPa (as‑cast) to 190 MPa (HT). In the alloy after preliminary heat treatment, deformation was localized in the coarse lamellar colonies formed during the cellular reaction, in which recrystallization/spheroidization of α₂/β/γ grains/particles developed sequentially. Application of the preliminary heat treatment increased the volume fraction of recrystallized/spheroidized grains/particles at ε = 70% from 35% (as‑cast) to 50% (HT).

The effect of Mo alloying on the mechanical performance of Ni–Fe alloys was investigated by first-principles density functional theory calculations within the plane-wave pseudopotential framework as implemented in CASTEP. The elastic constants, elastic moduli, tensile strength, and elastic anisotropy parameters of Mo-doped FeNi₃ systems were calculated and analyzed systematically. It was confirmed that all calculated structures accorded with the mechanical stability criteria, indicating their structural stability. Upon the introduction of a single Mo atom, the bulk modulus, Young’s modulus, and shear modulus were all found to increase. Meanwhile, the ideal tensile strength was enhanced to 1.45 GPa. The elastic moduli were decreased with further increase in Mo concentration, suggesting that excessive Mo addition reduces both stiffness and plastic resistance. Among the investigated configurations, both the highest B/G ratio and Poisson’s ratio were achieved in the Mo₃FeNi₃ system, indicating an improvement of ductility. In addition, with increasing Mo content, the anisotropy indices Aᵁ, Aᴮ, and Aᴳ were progressively reduced, indicating that the introduction of Mo plays a critical role in improving the plastic formability of the material and enhancing the stability of its mechanical properties. These results provide theoretical insights for the optimization of the mechanical performance of Ni–Fe alloys through Mo alloying.