Powder Metallurgy and Metal Ceramics最新文献

Chambersite (Mn₃B₇O₁₃Cl) precursor was prepared by the citric acid method, sodium borate dehydrate was used as a boron source, modified by cetyl trimethyl ammonium bromide (CTAB) as a surfactant, and its pH value was adjusted to 5 by ammonia. Mn₃B₇O₁₃Cl nanoparticles were prepared by sintering at 500, 560, 600, and 650°C, respectively, and then ground by mortar. The microstructure, surface morphology, and luminescent properties of the prepared nano-Mn₃B₇O₁₃Cl samples were analyzed by XRD, SEM, and fluorescence spectrometer. The effect of sintering temperature on the synthesis of manganese nano-Mn₃B₇O₁₃Cl powder was studied. The prepared nano-Mn₃B₇O₁₃Cl samples are spherical particles with irregular edges. When the sintering temperature is 650°C, the size of nanoparticles is the smallest, with an average size of 35 nm. When the excitation wavelength is 450 and 460 nm, the emission spectra of the nano-Mn₃B₇O₁₃Cl samples prepared at different sintering temperatures have two emission peaks. There is a green emission peak at 550 nm and a red emission peak at 652 nm. When the excitation wavelength is 470, 480, and 490 nm, the emission spectra of the nano-Mn₃B₇O₁₃Cl samples at different sintering temperatures have an emission peak in the range of green light band at 567, 589, and 601 nm, which is different from that at 450 nm and 460 nm. Under different excitation wavelengths, the emission peak intensity of the prepared nano-Mn₃B₇O₁₃Cl samples sintered at 560°C is the highest, and the luminescence performance is better. The lowest emission peak and luminescence properties of the nano-Mn₃B₇O₁₃Cl samples sintered at 500°C were studied. The excitation peak in the green band shifts to the orange band with increased excitation wavelength. The luminescence of the nano-Mn₃B₇O₁₃Cl samples prepared at different sintering temperatures is the ⁴T₁–⁶A₁ transition of Mn²⁺ ion.

The contact interaction between a hot-pressed chromium diboride ceramic material and an ironbased self-fluxing eutectic alloy (FeNiCrBSiC) was studied. The structure and phase composition of the starting self-fluxing FeNiCrBSiC alloy were analyzed. The starting alloy consisted of chromium–molybdenum carbides and chromium–iron borides distributed in a nickel-based metal matrix. The wetting kinetics in the FeNiCrBSiC–CrB₂ system was studied by the sessile drop method in vacuum at 1150°C. The iron-based self-fluxing alloy was found to wet the chromium diboride substrate to form contact angle θ = 12º. The structural and phase composition of the droplet and the contact interaction area in the FeNiCrBSiC–CrB₂ system were examined by electron microprobe analysis. The FeNiCrBSiC–CrB₂ system was characterized by intensive chemical interaction, which led to the redistribution of components in the interaction and droplet areas. In the wetting process, boron from the upper layer of the CrB₂ ceramic substrate diffused to the alloy area. Further interaction of boron with chromium–molybdenum carbides present in the starting FeNiCrBSiC alloy resulted in chromium–molybdenum carboborides with up to 24 GPa microhardness. The droplet area had a heterophase structure, consisting of a nickel- and iron-based metal matrix and inclusions of superhard chromium borides. The FeNiCrBSiC–CrB₂ system can be considered promising for the development of composite materials because intensive chemical interaction between the alloy and refractory components leads to additional superhard chromium–molybdenum borides and carboborides in the matrix, promoting greater wear resistance of thermal spray coatings of the composite material.

The production of powders with predetermined particle sizes is an important task in various branches of powder metallurgy and is especially relevant in additive manufacturing, where powders with an equivalent particle diameter smaller than 50 μm are used. The following parameters were calculated in the paper: theoretical gas flow speed to produce particles of required size by gas atomization of superheated fluid metal; specific flow rate of the metal flowing out of the metal tundish, and atomization nozzle parameters (such as critical and outlet cross-sectional areas and their ratio). Gas dynamics methods, being widespread in aviation engineering, were used to calculate the nozzle. The supersonic Laval nozzle parameters and gas dynamic parameters for atomization of the molten 10R6M5 tool steel were calculated at gauge gas pressures ranging from 0.5 to 2.0 MPa, allowing fine powders to be produced, including those with a particle size smaller than 50 μm. Graphical dependences were plotted to illustrate the theoretical speed at which particles of required size formed and the gas speed calculated as a function of the gas pressure before the atomization nozzle. A graphical method for determining the cross-sectional areas of the Laval nozzle and the inert gas flow speed for a given gauge pressure in the studied range was proposed. The following parameters for the production of 10R6M5 tool steel powders with a particle size smaller than 50 μm by gas atomization were established: gas flow speed at the nozzle outlet of 525 m/sec, temperature of –140°C, and pressure higher than 16.8 MPa. The calculated critical and outlet cross-sectional areas of the Laval nozzle were 110 and 290 mm² and their ratio was 0.379.

An overview of additive manufacturing techniques in Ukraine from the end of the last century to 2021 is presented. The current state of 3D printing in Ukraine was analyzed in terms of new developments (startups), research areas, and direct implementation of additive manufacturing techniques. The main scientific and research teams that were actively engaged in the development and implementation of additive manufacturing techniques in Ukraine since the end of the 1990s were addressed. They include those involved in research of selective laser sintering for ceramic powders produced from refractory ZrO₂–TiO₂ and TiN–TiB₂ compounds conducted at the Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, and research intended to produce 3D parts by fused deposition of metals or alloys called xBeam 3D Metal Printing conducted at the Paton Electric Welding Institute, National Academy of Sciences of Ukraine. This technique found its commercial implementation in the Chervona Hvilya PJSC startup. The paper discusses the main trends in the development of new equipment for 3D printing with ceramics, polymer/ceramic materials, and metals and alloys, as well as experiments combining different materials to achieve new properties. The latest experiments on the shape of materials are presented. They involve the formation of lattice structures that not only reduce the weight of parts but also impart properties that are comparable to those of dense materials. The main attention is paid to the overview of up-to-date capabilities and prospects for the use of additive manufacturing techniques and materials in national materials science. Attention is also focused on prospects for producing parts of complex shape for various functional purposes from ceramics, metals, and associated composites.

The Ukrainian Phase Diagrams and Thermodynamics Commission has been a member of the Alloy Phase Diagram International Commission (APDIC) for almost thirty years (since 1994). APDIC unites 18 member organizations involving 26 countries. The main tasks of APDIC are the exchange of scientific information and coordination of the activities of the international scientific community, mainly in the field of state diagrams and phase thermodynamics. The annual report of the Ukrainian Commission on the results of the activities of Ukrainian scientists in this field in 2021 was presented at the APDIC meeting on May 27, 2022. This information is presented in a table, collecting data on the systems studied and the result obtained and containing a list of references to published papers. Scientists from the Frantsevich Institute for Problems of Materials Science (National Academy of Sciences of Ukraine, Kyiv), Taras Shevchenko National University of Kyiv (Ministry of Education and Science of Ukraine, Kyiv), and Donbas State Engineering Academy (Ministry of Education and Science of Ukraine, Kramatorsk) provided relevant information to the Ukrainian Commission.

The partial and integral mixing enthalpies of Cu-Yb melts were first determined at 1453 K in the composition range 0 < x_Cu <0.7 by isoperibolic calorimetry. The Cu–Yb melts were established to form with the release of a small amount of heat: minimum mixing enthalpy ∆H = –9.7 ± 0.8 (at x_Cu = 0.7), which agrees with the published data for these melts in the composition range 0 <x_Yb < 0.3 at 1453 K and for other Cu–Ln systems. The model of ideal associated solutions was used to optimize and calculate all thermodynamic properties (Gibbs energies, enthalpies, and entropies of formation) for melts, intermetallic compounds, and associates in the Cu–Yb system. The calculated activities of components in the melts of this system exhibited moderate negative deviations from ideal solutions. The calculations with the ideal associated solution model also showed that ( varDelta {overline{H}}_{textrm{Yb}}^{infty } ) increased insignificantly and ( varDelta {overline{H}}_{textrm{Cu}}^{infty } ) more substantially in the Cu–Yb system with higher temperatures. The ideal associated solution model was applied to calculate temperature–composition dependences of the Gibbs energies, enthalpies, and entropies of formation for the melts and intermetallics to determine the coordinates of the liquidus curve in the studied phase diagram. The calculated and experimental data were in good agreement. Full information on the thermodynamic properties of all phases and phase equilibria in the Cu–Yb alloys was obtained.

The Cu–Ti–Zr system and associated multicomponent systems are of practical interest as their alloys show high bulk glass forming ability. The Cu–Ti–Zr system is divided into two independent subsystems (Ti–CuTi₂–CuZr₂–Zr and Cu–CuTi₂–CuZr) by the quasibinary vertical CuTi₂–CuZr₂ section. In this paper, phase equilibria in the Ti–CuTi₂–CuZr₂–Zr subsystem were experimentally studied. The structure of the as-cast binary and ternary alloys and the temperature of phase transformations in the samples that were cast and annealed at 750°C were studied by physicochemical analysis methods. The results were used to construct the liquidus and solidus surfaces, phase diagram, and vertical sections with 10, 20, and 30 at.% Cu, confirm the congruent formation of binary CuTi₂ and CuZr₂ compounds at 1012 and 1000°C, and find the composition and temperature of invariant eutectic reactions with their participation. The liquidus surface consists of two primary crystallization surfaces of infinite series of (βTi, βZr) (β) and Cu (Ti, Zr)₂ (γ) phases, which intersect along the univariant eutectic curve. The liquidus temperatures decrease from the boundary binary systems to the ternary one, reaching the minimum at 845 °C. The solidus surface is characterized by the coexistence of the β and γ phases (β + γ range) over the entire composition range. The copper solubility is from 5 to 8 at.% in the β phase and up to 2 at.% in the γ phase. This two-phase region is formed through the eutectic L ⇄ (βTi, βZr) + Cu (Ti, Zr)₂ reaction. There is also a minimum at 845°C on the solidus surface. The compositions of the two solid and one liquid phases coexisting at the minimum temperature are found on a single tie-line, along which the three-phase equilibrium is invariant. The compositions of the phases in this equilibrium are as follows: L_min—Cu₃₀Ti₃₇Zr₃₃, β_min—Cu_10.5Ti₆₂Zr_28.5, and γ_min—Cu₃₂Ti₃₅Zr₃₃ (at.%). According to differential thermal analysis, the minimum temperature of the eutectoid (βTi, βZr) ⇄ (αTi, αZr) + Cu(Ti,Zr)₂ transformation is 570°C.

The spark plasma parameters with electrodes produced from the high-entropy CrMnFeCoNi alloy were studied by mathematical modeling and experimentally. The model describes the dependence of the spark discharge plasma composition and the intensity of spectral lines on the electrode erosion rate and discharge power. The concentrations of electrons, atoms, and ions of electrode components and molecular components of plasma were determined from conditions of local thermodynamic equilibrium at the discharge axis (quasi-equilibrium conditions), and temperature was calculated from the energy balance equations. The system of nonlinear equations is solved in iterative cycles until self-consistent values of concentrations and temperatures are received. Elements with a high second ionization potential in electrode materials (for instance, Al, Cu, Ag, B) essentially increase temperature at the discharge axis resulting from reduction in the cross-section of inelastic processes and associated energy losses. Increase in the evaporation rate leads to temperature decrease, but electron concentration reduces by less than 20%, other parameters being equal. This effect results from decrease in the effective ionization potential with higher metal vapor concentration in the discharge plasma. There are complex nonlinear relations between the erosion rate and the intensity of spectral lines of atoms and singly charged and doubly charged ions, which are associated with the dependence of plasma temperature at the discharge axis on the evaporation rate. The calculated temperature and electron concentrations agree with the experiment within the error, taking into account the simplifications accepted in the model. The developed method can be used for spectroscopic diagnostics of electric erosion of the high-entropy CrMnFeCoNi alloy in the production of nanopowders by electrospark method and for emission spectral analysis of its composition.