Russian Journal of Non-Ferrous Metals最新文献

The article considers the influence of the parameters of friction stir welding modes on the formation of the outer surface and microstructure of the welded joint of sheets made of aluminum (AD1) and pure copper (M1). Changing the rotation speed of the welding tool from 600 to 1000 rpm and the range of welding speed from 20 to 100 mm/min allows one to control the amount of input energy, which allows one to transfer the welded materials to a plastic state. The paper considers the thermal cycles measured under the shoulder of the welding tool from the side of aluminum and copper sheets. The maximum temperature was 900 K on pure copper. The parameters of the welding modes also affect the formation of intermetallic layers. If the thickness of the intermetallic layer does not exceed 4–5 μm, then increased values of the mechanical strength of the welded dissimilar joint are observed.

Low corrosion resistance of magnesium alloys is a challenging problem that hinders their wide implementation in industry and medicine. In this regard, the study of the mechanisms and patterns of corrosion processes in magnesium and its alloys, including the analysis of the kinetics of these processes, is an urgent task. However, the set of methods available for studying the kinetics of corrosion with sufficient time resolution is very limited. Several studies have been published that demonstrated the high sensitivity of the acoustic emission (AE) method to corrosion processes occurring on the surface of magnesium alloys. Although these studies suggested that AE is associated with the release of hydrogen bubbles accompanying corrosion, no direct relationship has yet been established between the amount of hydrogen released and the AE characteristics. The present study aims at filling this gap. To conduct the study, a special setup with a corrosion cell was developed that allows monitoring changes in the volume of hydrogen released from the corroding surface of the sample, concurrently with recording AE signals and changes in the open-circuit potential (OCP) accompanying the corrosion process. Using this technique, the corrosion of ZK60 alloy in a 0.9% NaCl solution was examined. It was found that intense AE accompanied the corrosion process of this alloy from the beginning to the end of the test. A correlation was found between the AE characteristics, the volume of released hydrogen, and the OCP values at various intervals of the test. In particular, a linear relationship was discovered between the number of AE signals and the volume of hydrogen released during the corrosion process. The sensitivity of the method based on AE registration to the released hydrogen volume is shown to be several orders of magnitude higher than that of the conventional method of collecting hydrogen using a burette.

The study explores the mechanical assessment of thin film coatings through nanoindentation and nanoscratch testing methodologies, crucial for understanding and enhancing their mechanical properties. It examines the composition, microstructure, and behavior of various thin films, such as ZrAlN, TiCrN, and rGOF/EP, under different test settings. Nanoindentation measures hardness, elastic modulus, and plasticity index, providing insights into the impact of filler content and matrix interactions. The study highlights the importance of correct filler quantities and stoichiometric ratios for desired mechanical properties, as evidenced by nanoscratch testing, which measures adhesive strength, elastic restitution, and scratch resistance. Comprehensive testing in diverse settings and precise management of film composition and microstructure are emphasized to achieve optimal mechanical properties. Future research may explore novel materials, refine testing procedures, and develop predictive models, making nanoindentation and nanoscratch testing essential for advancing high-performance thin film coatings.

In this study, the wear performance of TiC reinforced A356 matrix composite materials produced by the mechanical alloying method at high temperatures was investigated. As a solid lubricant, 2% graphite, and four different amounts (3, 6, 9, and 12%) of TiC were added to the A356 alloy matrix. The prepared powders were mechanically alloyed in a planetary mill for 4 h. The composite powders produced were cold shaped (750 MPa) to obtain green compacts. The green compacts produced were sintered at 550°C for 60 min in a vacuum environment of 10^–6 mbar. TiC reinforced AMCs have been characterized by microstructure, hardness, and density measurements. Wear tests were carried out in a standard pin on disc type wear tester by adding a temperature module. In wear tests, two different loads (10 and 30 N), five different temperatures (20, 100, 180, 260, and 340°C), and three different sliding distances (53, 72, and 94 m) have been used. As a result of microstructure studies, it has been observed that the reinforcement material exhibits a homogeneous distribution in the structure. In hardness and density measurements, the highest hardness and density were obtained in the composite material with 12% TiC added. As a result of wear tests, the lowest weight loss was obtained in the composite material with 12% TiC added at all operating temperatures.

A comparative study of the hot deformation of the aluminum (8021) alloy with and without Sr addition under the conditions of deformation temperature of 350–500°C and strain rate of 0.01–10 s^–1 has been performed. The effect of adding 0.4% Sr on the microstructure of the alloy was investigated by EBSD and TEM, and the constitutive equations for the 8021 aluminum alloy with and without Sr were established. The results show that the hot activation energy decreases from 225.69 to 217.72 kJ/mol with the addition of 0.4% Sr to the alloy, which expands the safe processing range of the 8021 aluminum alloy. Compared with the alloy without Sr, the alloy with 0.4% Sr has a lower ln(Z) value. Adding Sr to the alloy decreases the density of dislocations, and it promotes the occurrence of dynamic recrystallization in the alloy, with an increase in the number of subgrains. The hot deformation behavior of the 8021 aluminum alloy is important for optimizing the alloy’s processing parameters and provides a reference for the industrial application of the 8021 aluminum alloy.

The use of multiple materials in the design and manufacturing of components enhances their operational characteristics. The application of additive technologies is promising for creating complex multi-material products. There are prospects for producing multi-material components from heat-resistant alloys, including nickel alloys, for the aerospace industry. The aim of this study was to investigate the influence of printing parameters using selective laser melting on the porosity and structure of bronze alloy BrKhTsrT V and VZh159, including the effect of heat treatment on the structure, chemical and phase composition, and the hardness of the transition zone in multi-materials. Multi-material samples were manufactured using an SLM 280HL selective laser melting system. Various regimes were used to study the impact of printing parameters on the porosity in the transition zone of the multi-material samples. On the basis of results of the conducted research, the following conclusions were drawn: only a significant increase in energy leads to a reduction in porosity in the transition zones of multi-material samples. Heat treatment according to regimes characteristic of the BrKhTsrT V alloy and the VZh159 alloy does not have a significant effect on the microstructure and chemical composition of the transition zones. The sizes of the transition zones were evaluated, measuring 300 µm when building the BrKhTsrT V alloy on VZh159 and 250 µm when building the VZh159 alloy on BrKhTsrT V, respectively. After heat treatment typical for each alloy, peaks corresponding to the phases of both alloys are observed in the transition zones. Different heat treatments significantly affect the microhardness of the alloys for which they are standard.

In this paper, titanium nitride particles (TNPs) reinforced copper-matrix graphite composites were prepared by powder metallurgy, in which copper-coated (Cu-coated) graphite (2 wt %) was used as solid lubricating phase and uncoated/Cu-coated TNPs (0, 1, 3, 5, 10, 15 wt %) was used as reinforcing phase. The effects of uncoated/Cu-coated TNPs on microstructure, density, porosity and mechanical properties of composites were studied and compared. The strengthening and wear mechanism of uncoated/Cu-coated TNPs in copper-matrix graphite composites were investigated. The results showed that electroless copper plating on the surface of TNPs can effectively improve the wettability between TNPs and copper matrix. In composites reinforced by Cu-coated TNPs, TNPs have a better interface bonding state with the matrix. Under the same content of TNPs, composites reinforced by Cu-coated TNPs have lower porosity, wear, friction coefficient, higher hardness and compressive strength than those reinforced by uncoated TNPs. TNPs can effectively strengthen the friction surface of composites. In processes of friction, TNPs will form a titanium oxide protective film on friction surfaces, which makes composites exhibit better self-lubrication, thus reducing the peeling wear. Copper plating can effectively reduce spalling of TNPs and weaken the abrasive wear and exfoliation wear of composites. Considering wear and friction coefficient, composites containing 3 wt % Cu-coated TNPs, exhibited better friction and wear resistance properties.

Self-dissolving medical implants, such as screws for bone fracture fixation or vascular stents, represent a promising application of magnesium alloys. Magnesium-based bioresorbable materials are currently not only the subject of research by scientific groups worldwide but also the raw material for producing commercial products—medical metallic implants that are actively used in patient treatment. Nevertheless, many technological issues remain unresolved. Chloride-containing fluxes are widely used in casting magnesium alloys. It is unclear whether the presence of flux particles in materials for bioresorbable implants poses a risk of corrosion damage to the surface of the product. This study investigates the processes of initiation and development of filiform corrosion caused by the presence of a chloride-containing particle on the metal surface. Energy-dispersive spectroscopy was used to determine the composition of corrosion products, and Kelvin probe atomic force microscopy was employed to measure their electrode potential relative to the magnesium matrix. It was shown that, under ambient temperature of 25°C and 30% humidity, filiform corrosion is initiated near the chloride-containing particle. Despite the shallow depth of damage (2–3 µm), corrosion spreads over a large area and is characterized by a high propagation rate (tens of microns per day). Analysis of the chemical composition of the corrosion products revealed that the process involves reactions leading to formation of hydroxide and its breakdown under the influence of chloride and CO₂. The corrosion products exhibit a positive potential relative to the metal, enabling the activation of anodic dissolution of the matrix. Placing the material in a vacuum completely halts progression of corrosion, which resumes upon exposure to air. This demonstrates the necessity of avoiding the use of chloride-containing fluxes in the production of bioresorbable alloys and storing finished products in a moisture-free environment whenever possible.

In this study, sulphuric acid was used to leach indium from zinc oxide dust, D2EHPA was applied to extract indium from the leaching solution, and hydrochloric acid was administered to strip indium from the indium-loaded organic phase. The effects of sulfuric acid concentration, temperature, leaching time and liquid-solid ratio on the leaching rate of indium were studied. The optimum leaching conditions for indium were as follows: sulfuric acid concentration of 200 g/L, leaching temperature of 80°C, leaching time of 120 min, and liquid-solid ratio of 8 : 1. Under these conditions, the leaching rates of indium, zinc, iron, and aluminum were 95.67, 97.97, 2.06, and 8.51%, respectively. On the contrary, lead was enriched in the leaching residue. Response surface analysis was carried out to further optimize the experimental conditions. The kinetic effects of temperature and sulphuric acid concentration on the indium leaching process were investigated using a shrinking-core model, and the activation energy of indium leaching was calculated to be 30.9 kJ/mol, with the kinetic model as: 1 – (1 – x)^1/3 = exp(5.11 – 3714/RT)t; 1 – 2x/3 – (1 – x)^2/3 = exp(8.84 + 3.599 ln[H₂SO₄])t. The results showed that the indium leaching process was controlled by a mixture of chemical reaction and diffusion, and the reaction stage of sulphuric acid was 3.599. Meanwhile, the McCabe-Thiel diagram for D2EHPA/HCl extraction/stripping of indium was constructed, and theoretically D2EHPA/HCl extraction/stripping of indium requires 2 stages to complete.