The study examines the thermodynamic regularities of carbide coating formation on steels during complex diffusion saturation processes involving chromium and titanium. The relevance of this research is determined by the need to enhance the wear resistance and durability of machine parts and tools operating under conditions of intensive friction, high temperatures, and aggressive environments. Special attention was given to modeling closed multicomponent thermodynamic systems Cr–Cl–C, Cr–Cl–C–Fe, and Cr–Cl–C–Ti under reduced pressure conditions. Thermodynamic analysis of the equilibrium state of the reactive environment was performed using the ASTRA software package in the temperature range of 600–1500 K at a constant pressure of 102 Pa. The composition of the gaseous and condensed phases was determined, and the influence of carbon, iron, and titanium content on the partial pressures of transition metal chlorides was studied. It was shown that the carbon content significantly affects the phase composition of chromium carbides in the condensed phase but practically does not change the partial pressures of its chlorides in the gaseous phase. The introduction of titanium was found to lead to the appearance of titanium chlorides in the gas phase and the formation of stable TiC carbide in the condensed state. Based on the obtained results, conclusions were drawn regarding the sequence of layer formation in complex carbide coatings during chrome-titanium treatment. It was shown that at low titanium content, the formation of chromium carbides predominates, whereas an increase in titanium concentration promotes titaniumization processes with the formation of a TiC layer. The results of thermodynamic modeling were confirmed by experimental studies of coatings on U8A steel, which demonstrated the formation of multilayer carbide coatings with enhanced microhardness. The obtained data can be used to optimize the technological parameters of diffusion saturation processes and to predict the phase composition of protective coatings.
Bronzes, particularly tin and aluminium bronzes, are widely used as antifriction materials in sliding units of machinery and energy equipment due to their combination of low friction coefficient, wear resistance, and corrosion resistance. However, their operational reliability is limited by intensive wear during the running-in period, when local overloads and surface micro-roughness lead to adhesive wear and scoring, reducing the efficiency of tribological components. The aim of this work is to investigate the structure and properties of multilayer coatings synthesized on bronze substrates by electrospark alloying (ESA) using a sulphur-containing paste. Samples of bronze BrO10S10 were treated on the "Elitron-22A" setup under various discharge energy modes. During ESA, the paste was applied before silver and tin alloying in the following sequence: paste → ESA with silver → ESA with tin → paste → ESA with silver. Surface roughness and topography were determined, and the distribution of microhardness and elements in the surface layer was analysed. The multilayer coating microstructure was studied using optical and scanning electron microscopy. Results revealed the formation of a multilayer structure: an outer layer with microhardness of 140-150 MPa, a lighter sublayer of 1250-2270 MPa, and a heat-affected zone of 778-1000 MPa. Intensive diffusion of electrode materials (Sn, Ag) and sulphur penetration into the bronze substrate were observed. The use of sulphur-containing paste enables controlled formation of structure and composition, enhancing coating adhesion. The study confirms that ESA can produce coatings with tailored mechanical properties, which is particularly important for tribological components with complex geometry and high loads. Therefore, the application of ESA with functional pastes is a promising approach for modifying bronze parts, optimizing the running-in process, and controlling surface layer properties, enabling the creation of coatings with high adhesion, enhanced wear resistance, and controlled composition for modern mechanical engineering and energy applications.
A method for casting shell cases for technical purposes with a predicted nature of destruction has been substantiated and developed. The relevance of the research is driven by the need to create lightweight metal structures capable of controlled fragmentation into elements of a given mass under intensive high-energy impact, which is critical for single-use systems. Since traditional mechanical execution of grooves on the internal cavities of thin-walled bodies is economically inefficient and technologically complex, it is practically not used in mass production. The scientific novelty of the study lies in the mathematical substantiation of a geometric fragmentation criterion, which establishes an analytical relationship between the metal density, wall thickness, and the area of the section bounded by distribution grooves. The proposed criterion allows, at the design stage of the pattern tooling, to ensure the formation of fragments in the optimal mass range of 2 to 5 grams. This meets the requirements of functional efficiency through the implementation of the "gas wedge" physical effect. The paper describes the technological process of implementing the method using Lost Foam Casting (LFC). It is proved that the use of polymer patterns allows for the precise transfer of the complex geometry of stress concentrators from the mold directly into the casting, ensuring high surface quality and dimensional accuracy. Practical approbation of the method using the example of manufacturing cylindrical shell bodies from gray cast iron confirmed the possibility of producing a ribbed internal surface of the casting. The possibility of integrating such products with modern autonomous transport systems is considered, and a method for automatic unloading based on polymer fasteners that are thermally destroyed by an electrical signal is developed. The integrated approach, combining precision casting of bodies and innovative delivery methods, allows for reducing the metal consumption of production and increasing the efficiency of autonomous transport systems.
The paper presents the results of a comprehensive investigation of the microstructural state and mechanical properties of high-pressure turbine blades of the GTC-10I gas turbine unit manufactured from the heat-resistant nickel-based alloy ChS70-VI after long-term industrial service. The study was carried out on blades with operating times of 20,000, 30,000, and 50,000 hours, which made it possible to analyze the evolution of the material structure at different stages of service life. Metallographic examination revealed characteristic features of microstructural degradation in the blade airfoil material as a function of service duration and operating temperature. It was shown that prolonged exposure leads to progressive coarsening and coagulation of the strengthening γ′ phase, accompanied by a decrease in its dispersion and redistribution of phase constituents. The most pronounced structural changes were observed in the high-temperature regions of the airfoil, whereas the blade root section, operating under lower temperature conditions, retained a relatively stable microstructural state throughout the investigated service period. Mechanical testing demonstrated a gradual reduction in both strength and ductility with increasing service time, which correlates well with the observed microstructural transformations. After 50,000 hours of operation, the structural changes become largely irreversible and are accompanied by a sharp deterioration of mechanical properties, indicating a limiting condition for further safe operation of the blades without refurbishment or recovery procedures. The obtained results can be applied to residual life assessment of GTC-10I high-pressure turbine blades made of the ChS70-VI alloy and to substantiation of allowable service limits for industrial gas turbine units operating under long-term thermal loading.
The article presents the results of the St3 steel surface zone study after electric-spark alloying (ESA) by chromium, titanium and zirconium in combined saturating environments. The peculiarity of such treatment is the combination of environments of different chemical composition and aggregate state within the framework of one technological process. The treatment is carried out in two stages: ESA in liquid nitrogen and ESA in glycerin. The liquid nitrogen environment allows to rapidly reduce the temperature of the alloying electrode and cathode, which contributes to an increase in the penetration depth of anode metal atoms deep into the steel base. The glycerin environment acts as a source of carbon, which appears as a result of partial dissociation at the boiling temperature under the action of a spark discharge in local volumes of the liquid. The choice of anode materials was determined by their ability to form carbides and nitrides. Extreme conditions of the ESA process, under which chromium, titanium and zirconium interact with elements of the environment (nitrogen and carbon), contribute to the formation of coatings enriched with different types of penetration phases. Microstructural analysis revealed that by ESA with a change of environments in the sequence liquid nitrogen – glycerin, coatings with a thickness of 30 – 40 μm are formed. The surface alloyed layers composition on St3 steel is multiphase and depends on the material of the alloying electrode (Cr, Ti, Zr). The microhardness of the studied coatings on St3 steel is 4.3 – 5.7 GPa due to the presence of carbides, nitrides of transition metals, as well as intermetallics and solid solutions with the base material. The distribution of microhardness deep into the steel base showed its increased values up to 70 μm, which may be caused by the complex effect of temperature and of the environment density. Temperature gradients during ESA in liquid nitrogen contribute to a rapid increase in the penetration depth of anode metal atoms deep into the samples. Further alloying in glycerin causes diffusion processes of saturation of coatings and the base with non-metallic inclusions from the liquid environment, which lead to the appearance of carbide particles on clusters of dislocations formed at the previous stage of processing.
Based on the analysis of patent solutions for reinforcement methods, the article investigates the technological features of manufacturing reinforced and bimetallic castings using the lost foam casting (LFC) method. The authors analyze the drawbacks of traditional reinforcement methods in hollow sand molds, the most critical of which are the difficulty of spatial fixation of the reinforcement, the risks of displacement of its elements during mold tilting or transportation, and the high probability of destruction of the sand mold surface when mounting the reinforcement to its walls. The concept of using a polymer pattern not only as a shaping element but also as a reliable mounting base is substantiated. This approach allows for the integration of reinforcing components directly into the pattern body, ensuring high positioning accuracy in the future casting. The dual functional role of the reinforcing elements is noted: in addition to mechanical strengthening, they act as internal micro-chillers, which allows for effective control of crystallization processes, refinement of the metal structure, and minimization of shrinkage defects in massive sections. Attention is also paid to the synergy of the LFC process with additive technologies. The use of 3D printing of polymer patterns makes it possible to create internal niches in the pattern and place reinforcement in them with high geometric precision. The paper presents the practical implementation of this technique on the example of the development of a cast armored barrier with integrated spring elements. The mechanism of the TRIP effect (transformation-induced plasticity) realization for hardened iron-carbon alloys is described, where spring structures act as accumulators of phase transformation energy, which increases the survivability of the structure under dynamic and impact loads. The proposed technology opens up new opportunities for the production of lightweight metal products with differentiated properties, intelligent means of passive protection, and highly loaded mechanical engineering parts.
The structural and chemical heterogeneity of two Al-based complex concentrated alloys Al–Cr–Mn–Fe–Ni–Cu and Al–Cr–Mn–Fe–Co–Ni–Cu–Zn was investigated in the as-cast condition in order to evaluate the predictive capability of commonly used high-entropy alloy (HEA) descriptors. Integral thermodynamic parameters (ΔSmix, ΔHmix, δ, VEC, Ω, Δχ) calculated for both compositions fall within ranges typically considered favorable for solid-solution formation in HEA and complex concentrated alloys. In particular, ΔHmix and δ satisfy empirical stability criteria, while Ω exceeds commonly proposed thresholds for solid-solution formation. However, microstructural characterization reveals that these descriptors alone do not reliably predict the actual phase constitution in as-cast state. SEM/EDS analysis showed that both systems form a chemically heterogeneous dendritic-like morphology, accompanied by pronounced chemical partitioning between chemically distinct microstructural regions. In the Al–Cr–Mn–Fe–Ni–Cu alloy, two chemically distinct microstructural constituents were identified; however, both of them may correspond to B2-type intermetallic phases with a BCC-related lattice. Although VEC values fall within ranges associated with BCC or mixed BCC/FCC tendencies in Al-rich multicomponent alloys, experimental evidence indicates that the dominant structural constituents correspond to ordered intermetallic phases rather than disordered solid solutions. In contrast, the Al–Cr–Mn–Fe–Co–Ni–Cu–Zn alloy exhibits significantly higher chemical and morphological heterogeneity. Addition of Co and Zn leads to increased microstructural complexity and decrease of Cu-driven chemical separation. Local enrichment in Cu and Zn was detected in chemically distinct regions, indicating a strong tendency toward chemical separation and suggesting the formation of brass-type intermetallic phases.
This study is focused on the development and comprehensive analysis of the structural state and mechanical properties of a high-strength wrought aluminum alloy of the Al–Zn–Mg–Cu system, additionally alloyed with scandium (Sc) and zirconium (Zr). Alloys of this system are critically important materials for the aviation and defense industries due to their exceptional specific strength. The research addresses common challenges inherent to high-alloyed systems, such as susceptibility to hot cracking and dendritic segregation, by optimizing alloying element content and implementing innovative casting techniques. The scientific novelty of this work lies in the investigation of the synergistic effect of Sc and Zr on the alloy's microstructure specifically in the as-cast state, an area less explored compared to wrought semi-finished products. It was established that the formation of Al3(Sc, Zr) intermetallic compounds ensures significant grain refinement, enhances anti-recrystallization stability, and contributes to additional strengthening through the precipitation of secondary coherent nanoparticles that remain stable during subsequent heat treatment. The practical part of the research involved the production of a large-scale industrial ingot (150 mm in diameter) using a vacuum magnetohydrodynamic (MHD) installation and continuous casting into a short crystallizer with a thermal filling. This approach facilitated a uniform globular structure free of gas porosity, achieving a record-low hydrogen content (0.04–0.05 cm³/100 g). The evolution of the microstructure and phase transformations was studied using SEM, EDS, and DSC methods. Mechanical testing results demonstrated that the applied casting technology ensures high isotropy of properties in both longitudinal and transverse directions. The alloy was found to exhibit high technological plasticity (elongation up to 53%) at temperatures of 300–400 °C, allowing for the optimization of further thermomechanical processing parameters, such as forging and rolling. The initial interphase melting temperature was determined to be 471–477 °C, serving as a fundamental parameter for establishing precise homogenization and solution treatment regimes for the experimental alloy.
This study investigates the possibility of using high-entropy alloys (HEAs) as a binder phase in cubic boron nitride (cBN)-based superhard composite materials. A series of Ni–Fe–Cr–Co–Ti–Al system alloys with varying aluminum content was developed and melted, ensuring the formation of single-phase, two-phase, eutectic, and multiphase structures. The relevance of this work is driven by the need to overcome the limitations of traditional metallic and ceramic binders (insufficient wettability, brittleness, high sintering temperatures) for the development of efficient cutting tools. The aim of this work is to establish the influence of the phase composition of HEAs on their reactivity with cBN and to assess the application potential of such alloys as a binder phase for cBN-based superhard composite materials. Five alloys with different aluminum contents were melted. Using methods of synchronous thermal analysis (DSC/TG), ultrasonic spectroscopy, and high-pressure (7.7 GPa) high-temperature sintering, the thermophysical properties of the alloys, their interaction with cBN, as well as the mechanical characteristics of the superhard composite materials (Vickers hardness, Young's modulus, fracture toughness) were investigated. It was found that the phase composition significantly affects the reactivity of the alloys with cBN. It was shown that maximum interaction activity is characteristic of alloys in which titanium is in solid solution, whereas its concentration in ordered phases (of the B2 type) reduces reactivity. Superhard cBN composites were obtained by high-temperature pressing at a pressure of 7.7 GPa and temperatures up to 2200 °C. It was established that the developed materials are characterized by high values of hardness, Young's modulus, and fracture toughness (K₁C = 8–9 MPa·m¹/²), which are comparable to or exceed those of industrial materials. It was shown that the increased fracture toughness is due to the implementation of crack deflection and crack bridging mechanisms facilitated by micron-sized HEA inclusions in the intergranular space of the cBN matrix. The obtained results confirm the promise of using high-entropy alloys as an effective binder for the creation of a new generation of superhard composite materials.
The study of the structure, physicochemical, and operational properties of materials is an essential prerequisite for their scientifically grounded selection and for ensuring operational reliability and durability. To ensure a unified approach to material property assessment and to increase the reliability and reproducibility of test results in Ukraine, modern State Standards of Ukraine (DSTU) are applied. These standards are harmonized with international (ISO, ASTM) and European (EN) regulatory documents. The challenge of standard harmonization lies in the necessity to align the national regulatory framework with international requirements, eliminate technical discrepancies, and ensure mutual compliance, while considering modern achievements in materials science and industrial needs. The digitalization of regulatory documents and ensuring their accessibility for industrial enterprises, research institutions, and higher and vocational education establishments remains a pressing issue. Specifically for the metallurgical industry, the standards effective or cancelled as of January 1, 2026, were reviewed, including those without harmonized counterparts. This allows for an assessment of the regulatory framework's completeness and consistency, identifying existing gaps and determining priority areas for further development and harmonization. This paper performs a comparative analysis of national, international, and European regulatory documents governing the methods for determining the physicochemical and operational properties of materials, as well as conducting metallographic examinations. Key trends in standard harmonization are identified, particularly regarding the unification of testing methods, alignment of requirements for sample preparation and result interpretation, and the adaptation of the national regulatory base to international and European approaches. A comprehensive set of measures aimed at accelerating the harmonization of Ukraine's national standards with international and European regulatory documents is proposed. It is demonstrated that the prospects for further research in the field of materials science standardization are linked to improving the efficiency of quality management systems in accordance with European Union requirements.
High-carbon wire for the production of the steel cord and reinforcement of the high-pressure hoses with a diameter up to 0.05 mm is made from the wire rod with a diameter of 5.5 mm by drawing with intermediate patenting and has high strength and ductility properties. The specified set of the properties are achieved through optimal heat treatment and formation of the structure of the finely dispersed perlite (sorbite, troostite) during the patenting process. The formation of the martensite, also the significant amount of the bainite and excess ferrite in the structure of the patented steel is not allowed. Existing patenting modes lead to formation of the bainite structure along with finely dispersed pearlite structures, shown by microstructural investigations. Depending on the heat treatment (patenting) modes, it is possible to formation not only different quantities, but also different types of the bainite, which have different effects on the mechanical properties of the patented wire and the technology elaboration. The aim of the research was to establish patterns of the influence of the processing temperature (patenting) on the mechanical properties of the patented high-carbon wire. In the entire studied range of the austenite transformation temperatures, bainite is formed along with sorbite, and a decrease in the patenting temperature increases the amount of bainite, as shown by the analysis of the mechanical properties and microstructure of the C80D2 steel samples after isothermal decomposition of the austenite at patenting temperatures of 610–530°C. The amount, morphology and distribution pattern of the bainite have a significant effect on the mechanical properties of the patented blank made of the high-carbon steel C80D2 at a patenting temperature below 560°C, when its proportion in the microstructure exceeds 10%.The most optimal combination of the mechanical properties and microstructures are achieved when patenting at a temperature of 590–560°C.
The article examines the impact of normalization on key quantitative parameters of the microstructure of as-cast structural steel, such as grain length, width, shape factor, grain area, and the total area of ferrite and pearlite. The capabilities of microstructure analysis using computer image analysis software are demonstrated, in comparison with the study of microstructure using reference scales. It was established that after normalization from 865 °C, the length and width of ferrite grains decreased by factors of 1.88 and 2.33, respectively; the shape factor decreased by 10–12%; the average area of a ferrite grain decreased by a factor of 4.78–5.18; while the total area of ferrite increased by a factor of 1.3–1.5. The length and width of pearlite grains decreased by factors of 2.21 and 2.01, respectively; the shape factor decreased by 3–12%; the average area of a pearlite grain decreased by a factor of 3.96–4.02; and the total area of pearlite decreased by 2–15%. It is shown that the refinement (dispersion) of the steel microstructure occurs due to an increase in the percentage of structural elements with smaller sizes. The proportion of ferrite grains with length and width in the range of 10–20 μm increased from 39% and 85% in the initial state to 91% and 97% after normalization, i.e., by a factor of 2.3 and by 14%, respectively. The proportion of grains with a shape factor of 2 increased by 8%, and the proportion of ferrite grains with an area in the range of 100–300 μm² after normalization reached 94%, which is 2.1 times higher than in the initial state. It was established that the distribution of pearlite in the microstructure of as-cast steel after normalization is characterized by the following: the proportion of pearlite grains with length and width in the range of 10–50 μm changed from 85% to 100% and from 95% to 100% of cases, respectively; the shape factor in 99% of cases was within the 1–4 range. The value of the average pearlite grain area in the as-cast state was within the 0–1750 μm² range in 98% of cases, while after normalization it was within 0–1250 μm² in 99% of cases. It is shown that the total area of ferrite in the as-cast state was 100% within the range of 15–30 μm², and after normalization within 15–45 μm². The total area of pearlite in a similar interval changed from 75–90 μm² to 60–90 μm², respectively. The materials of the article can be used by researchers for the quantitative analysis of the influence of external factors on the microstructure of metals and alloys.
The microstructure and granulometric characteristics of spherical powders of heat-resistant nickel alloys were studied. Metallographic examinations were conducted using a Thermo Scientific Apreo 2C scanning electron microscope (Thermo Fisher Scientific, Waltham, MA, USA), and elemental composition was analyzed using a SER-01 «ElvaxLight» X-ray spectrometer. Granulometric characteristics of the powders were evaluated using ImageJ image analysis software. Bulk density and flowability measurements were carried out in accordance with DSTU/ISO 3923-2:2016 and DSTU/ISO 4490:2016 standards. The surface morphology of spherical powder particles of CrNi50WMoTiAlNb and CrNi60WTi alloys was investigated for two particle size fractions: 50…200 µm and ≤63 µm. It was demonstrated that the studied powder fractions consist of spherical particles with well-developed, regular dendritic surface microstructures. Granulometric analysis results were used to construct particle size distribution histograms. For the 50…200 µm fraction of CrNi50WMoTiAlNb, particles with a mean diameter of 136 µm and a polydispersity of 4.1% predominated, while for the ≤63 µm fraction, the mean diameter was 45.6 µm with a polydispersity of 7.6%. For CrNi60WTi, the 50…200 µm fraction was dominated by particles with a mean diameter of 124 µm and a polydispersity of 4.9%, whereas the ≤63 µm fraction had a mean diameter of 29.7 µm and a polydispersity of 8.3%. Measurements of bulk density and flowability for the spherical powders of CrNi50WMoTiAlNb and CrNi60WTi indicated that decreasing particle size leads to increased polydispersity and bulk density. Fine powders (≤63 µm) exhibited reduced flowability due to enhanced interparticle adhesion. These results suggest that higher polydispersity ensures denser powder packing but limits powder rheological performance, which is a critical factor when preparing feedstock materials for additive manufacturing processes.
The authors investigated the formation of the structure and properties of cast billets made from a transparent organic camphene-based alloy and an aluminum alloy AD31, depending on the conditions of their crystallization, including under external physical influences. It was shown that the structural formation of all billets occurs according to the same patterns, regardless of the alloy type and crystallization conditions. It was established that in the control billets (i.e., without external influence), crystallization mainly proceeds according to the scheme of sequential solidification, as clearly evidenced by their macrostructures, which consist only of columnar crystal zones. During the formation of experimental billets (i.e., under vibrational influence), significant changes in the crystallization conditions occur, leading to a mixed solidification scheme. Visual observations of the formation of experimental camphene alloy billets and macrostructure analysis of AD31 aluminum alloy billets showed that, at the initial stage, the nucleation and growth of only columnar crystals take place, meaning that solidification occurs sequentially. As the columnar crystals reach a certain size (length), they undergo partial destruction under the influence of bending stresses of elastic waves, and the crystal fragments, due to vibrational mixing, are evenly distributed throughout the cross-section of the solidifying melt. At the same time, the appearance of supercooled micro-volumes of the melt around each crystal fragment causes accelerated cooling of the remaining liquid core of the billet, thereby ensuring its subsequent volumetric solidification. As a result of such vibrational effects during billet formation, the structural heterogeneity decreases and the dispersion of the cast grain significantly increases. A natural consequence of these structural changes in the experimental billets is the improvement of the physicomechanical properties of the cast metal, accompanied by a decrease in their anisotropy across different zones.
This work is dedicated to developing a technological basis for optimizing the chemical composition, structure, and mechanical properties of secondary aluminum alloys obtained from the recycling of various types of aluminum scrap, including military and industrial origins. The relevance of this research is driven by the necessity for rational utilization of secondary raw materials, reduced energy consumption, and minimized environmental impact in the production of high-strength structural materials for the aviation and machine-building industries. A remelting technology utilizing a binary NaCl-KCl salt flux system is proposed. This system ensures effective melt refining from non-metallic inclusions, intensifies degassing, and reduces the loss of alloying elements. An approach involving zinc (Zn) alloying is introduced to adjust the chemical composition of the secondary alloy, facilitating the formation of a high-strength Al-Zn-Mg system. It is demonstrated that zinc alloying and additional flux treatment contribute to a reduction of harmful iron (Fe) impurities to 0.36-0.38%, a transformation in the morphology of iron-containing intermetallic phases, and a decrease in residual casting stresses. Metallographic and microstructural analyses confirmed the formation of a more homogeneous, fine-grained cast structure with a reduced defect density. The mechanical properties of the alloy in the as-cast state were determined: an ultimate tensile strength of 140 MPa and an elongation of 5.42%, which corresponds to an intermediate stage of property development prior to subsequent heat treatment. The results confirm the potential of the developed technology as an effective foundation for producing secondary high-strength aluminum alloys with predictable structural and mechanical properties, suitable for practical application in critical structural components for aviation and general machine-building.
The improvement of the design of modern heat engines is characterized by the expansion of the use of heat-resistant fibrous metal composites (MCM). An important feature of these materials is that their properties can be purposefully changed in the necessary directions depending on the loading scheme of a particular part. The component that largely determines the strength and technological properties of such a composite is the fibers. Currently, the requirements for the properties of reinforcing fibers are quite fully met by tungsten alloy wires, and the use of short pulse heating is promising for the formation of the composite. However, in the case of irrationally set values of the parameters of the formation process, pulse heating can lead to an unjustified decrease in the properties of the fibers, in particular strength and plasticity at temperatures around 20°C. Therefore, in order to rationally select the alloy grade for fibers and CM formation modes that do not lead to an unjustified decrease in the properties of reinforcing fibers, this work studied the influence of pulse heating parameters, in particular, the heating rate and the maximum achievable temperature on the properties of fibers from tungsten-rhenium and molybdenum-rhenium alloys. To investigate changes in fiber properties, under the influence of technological heating, the heating of fibers was simulated, which occurs during the CM formation process by passing electric current pulses of different power through their samples. It was found that reinforcing fibers from a tungsten-rhenium alloy containing about 5% rhenium become brittle after pulse heating to temperatures (above 2000°C) necessary for the formation of a defect-free MKM structure, and wires from tungsten-rhenium alloys containing about 27% rhenium retain their plasticity at a temperature of 20°C after pulse heating up to melting temperatures.
The paper presents the results of a study of the possibility of using powder metallurgy methods in obtaining cast titanium bronzes by using titanium-copper alloys obtained by thermal synthesis from a mixture of titanium hydride and copper powders as an alloying component. The conducted studies allowed optimizing the parameters for obtaining titanium intermetallics of the Ti-Cu and Ti-Cu-Al systems using metal powders as the starting material, and experiments were conducted on melting titanium bronzes using the developed powder alloys. Experimental melting of titanium bronze ingots was carried out for three bronze compositions: Cu - 2.7% Ti; Cu - 2.7% Ti - 0.5% Al and Cu - 2.7% Ti % - 1.0 % Al. As the results of the research showed, alloying of the copper melt with powder alloys made it possible to obtain cast alloys, the structure of which consists of a copper matrix phase with evenly distributed inclusions of copper-titanium intermetallic grains with a size of 2-8 microns. Experiments on smelting titanium bronze ingots also showed that the use of synthesized powder alloys significantly accelerates the smelting process, eliminates the need to use high temperatures required for dissolving pure titanium, and thereby reduces the burnout of alloying components, which allows for more accurate adherence to the specified chemical composition of the bronze. The study of the influence of heat treatment modes on the structure and physical and mechanical properties of cast titanium bronzes showed that after quenching of castings from 800 °С, the structure of cast alloys has a significantly dendritic character and noticeably lower hardness compared to the cast state. A significant increase in the level of hardness and strength of alloys is achieved by aging at 400 °С. The highest level of hardness and strength is noted for the Cu - 2.7% Ti alloy without aluminum. The dependence of the electrical conductivity of bronze, additionally alloyed with 0.5% Al and 3.0 % (wt.) Ni, on the titanium content is extreme: the maximum conductivity (~33 % IACS) is observed for the alloy with 1.5% (wt.) Ti.
This work is devoted to the study of the mechanisms of crystal nucleation in metal melts depending on their shape and volume. The method of physical modeling was applied, using low-temperature (tmlt. ≤ 70 ° C) Wood’s metal alloy and transparent organic media such as camphene and diphenylamine. The experiments were conducted on two types of test specimens: flat samples of small thickness (δ = 0.2 mm) and bulk samples of larger volume in glass tubes (Ø 8 mm). The transparency of the media and the small thickness of the flat samples made it possible to visually observe the crystallization process and determine the degree of supercooling based on the coolant temperature at which the first crystal appeared. The supercooling level of the bulk samples was determined by characteristic features on their cooling temperature curve — namely, the appearance of plateaus due to the release of crystallization heat. As a result of the study, it was demonstrated that the rate of nucleation in flat samples of model media directly depends on the activity of the mold wall surfaces. The activity of these surfaces, in turn, is significantly influenced by the degree of overheating of the model melts above the liquidus temperature and the level of their supercooling. In experiments with bulk samples, it was found that, in addition to the activity of the mold wall surfaces, the dependence of the supercooling of the studied media on their overheating is also affected by factors such as the activity of present impurities, as well as fluctuations in temperature and density.
Devices that operate under high-speed deformation conditions are used in civil and military industries. A key component of these products is the shaped charge liners, the materials for the manufacture of which must have high plasticity to ensure the integrity of the jets formed during explosive loading. The purpose of the work is to analyze the research results on the influence of materials' nature and shaped charges liner producing technologies on their high-speed deformation, and the creation of a reinforced composite material with a copper matrix to manufacture a complex thin-walled shape product. To achieve the goal, copper electrodeposition was used as the most effective method for obtaining thin-walled liners. It was established that the concentration of the CuSO4 solution of 0,8 mol/l, the current density from 0.06 to 0.1 A/cm2 and the duration of electrodeposition of 3 h are the optimal parameters of copper electrodeposition process on the nickel mesh. Composite material microstructure analysis showed that the initially deposited copper repeats the shape and dimensions of the nickel mesh as a substrate, but the mesh holes do not grow. To increase the density and integrity of the copper composite reinforced with nickel fibers, additional pressing was carried out in steel molds. This operation was combined with calibration and providing precise (not less than 0,1 mm) dimensions and shape to a thin-walled product with a density uniformity of not less than 1 % by volume. It was established that during plastic deformation, the gaps between the particles of copper deposited on the nickel surface are filled and a solid material is formed. An experimental sample of a conical shaped charge liner made of copper-nickel composite material has been manufactured for further research.
The article investigates the influence of the flux-cored wire (FCW) core composition on the structure and mechanical properties of the deposited metal. It is demonstrated that a promising approach to controlling the structure and properties of the deposited metal is the use of chemically pure granulated metallic powders in the FCW core instead of ferroalloy powders. This modification stabilizes the deposition process and enhances the uniformity of the microstructure. The study aims to compare the microstructure and mechanical properties of the deposited metal obtained using FCWs with granulated PG-10R6M5 powder of two different fractions and a conventional ferroalloy-based mixture. Experimental results indicate that specimens produced by deposition with FCW containing granulated powder exhibit a fine-grained structure and greater homogeneity. Metallographic analysis of specimens obtained using ferroalloy-based FCW revealed the presence of large non-metallic inclusions (up to 100 μm) and microdefects, which negatively affect the mechanical properties. Hardness and microstructure analysis demonstrated that the metal deposited using FCW with fine-fraction granulated metallic powder (50–100 μm) exhibits the most favorable combination of mechanical properties, including increased strength and improved ductility compared to the metal obtained with a ferroalloy-core FCW. This improvement is attributed to the reduction in microdefects and the stabilization of the structure during deposition. The chemical composition of the deposited metal in all studied cases corresponds to 25Kh2V2M2FS steel, confirming compliance with established requirements. The research findings validate the feasibility of using granulated metallic powders in the FCW core as an alternative to ferroalloys. This approach ensures a more uniform microstructure, a lower level of non-metallic inclusions, and enhanced mechanical properties, contributing to the increased durability and reliability of deposited components in critical structural applications.
