Tungsten oxide is widely used in the photolysis of water for hydrogen production, photocatalysis, photoelectric conversion, and electrochromism. Eu3+ doped tungsten trioxide nanoparticles were prepared by hydrothermal method with the addition of sodium tungstate (NaWO4 · 2H2O). Two different samples were obtained at the temperature set at 160 and 180°C. The third sample obtained from ammonium paratungstate ((NH4)10H2(W2O7)6) was used at the temperature of 160°C. The samples’ morphology, structure, and optical performance were then observed and analyzed. The results show that a rod-like structure of WO3 : Eu3+ nanoparticle with a monoclinic crystal system can be successfully generated using sodium tungstate. A spherical structure of WO3 : Eu3+ nanoparticle with a triclinic crystal system was prepared using ammonium paratungstate. The finished sample with ammonium paratungstate at a reaction temperature of 160°C has the smallest grain average size of 45.98 nm and Eu3+ ions successfully doped. Under the excitation of different wavelengths, the three samples demonstrate pronounced emission peaks at around 615 nm, corresponding to the 5D0 → 7F2 electronic transition of Eu3+. Using ammonium paratungstate as the tungsten source, the prepared WO3 : Eu3+ nanoparticle at 160°C has the highest luminous intensity. The luminescence intensity of the prepared WO3 : Eu3+ nanoparticle from ammonium paratungstate as a tungsten source is higher than the other two samples obtained from sodium tungstate as a tungsten source at two temperatures. However, the three samples with excitation wavelength λ = 254 nm were monitored at the wavelength of 615 nm. All three samples exhibited the most substantial excitation peaks at about 508 nm, which belonged to the electron transition in 4f of Eu3+.

The structurization and phase composition of the alloys produced by in situ thermal synthesis at 1200°C from TiH2–Fe–Ni–B4C powder mixtures were studied. To assess how the mixture composition influenced the structure and properties of the synthesized alloys, five different mixture compositions were prepared. The iron and nickel contents were varied and the content of thermally reacting components (titanium hydride and boron carbide) remained unchanged in all mixtures and was 64 and 16%. Microstructural and X-ray diffraction analyses were conducted for the sintered samples, and the microhardness and particle size distribution were determined for each composition. The resultant composite alloys had a substantially heterophase structure as a basic skeleton consisting of titanium carbide and diboride compounds and a cementing layer consisting of intermetallics and iron and nickel solid solutions. The main alloy phase was titanium carbide, TiCx, whose stoichiometry x varied from 0.43 to 0.54. The introduction of 5% Ni into the mixture somewhat increased the stoichiometry of titanium carbide, but 10% and higher nickel content decreased the stoichiometry. The alloys produced from nickel-containing mixtures had a finer microstructure than the nickel-free alloy did, and all composites in the Fe–Ti–Ni–B4C system were characterized by a significantly finer structure than the boron-free Fe–Ti–Ni–C alloys. The introduction of nickel to the composition also somewhat increased the average microhardness of the synthesized composite.

The effect of nickel, tin, and indium additions in the eutectic Ag–28 wt.% Cu filler on the capillary and contact processes in brazing of VK94-1 and VK100 alumina ceramics and leucosapphire with VT1-0 titanium was examined. A special technique to study such processes was developed. This technique allows identifying, to the extent possible, the effect of different process parameters (heating rate, holding time, degree of vacuum, etc.) on the contact angles formed by metallic melts with different compositions on nonmetals in one experiment. High-temperature capillary and optical and scanning microscopy methods established that even small additions of nickel, tin, or indium to the eutectic Ag–Cu melt noticeably influenced the titanium dissolution rate and incipient wetting temperature of the nonmetallic substrate. Nickel additions were shown to enhance melt separation in the Ag–Cu–Ti system; in particular, the amount of the copper-based phase, eutectically melting with titanium above 870°C, increased. The effect of these additions in the Ag–28 wt.% Cu filler on the strength of brazed ceramic–ceramic joints produced using titanium foil inserts was studied. The results were discussed involving thermodynamic characteristics of the contacting structures. The role played by the type of chemical bonds in products resulting from interaction of the melt components and the solid substrate on the contact angle was shown. Brazed joints of alumina ceramics were made and used to determine the three-point-bending strength. The effect of various additions to the Ag–28 wt.% Cu filler on brazing strength was examined. Indium was found to be the most promising addition to the silver–copper filler as it allowed the brazing temperature to be controlled without a significant change in the mechanical strength of brazed joints.

The application of ceramic dielectrics in various microwave electronic instruments and devices is determined by their properties such as dielectric constant, dielectric loss factor, thermal conductivity, and absorptance. Alumina nitride composites with dielectric losses (high dielectric loss tangent tgδ varying from 0.1 to 0.6) are promising functional materials, but there are few publications with detailed dielectric characteristics including thermal conductivity, which is especially important for devices with high output power. To determine the dielectric characteristics (ε′ and tgδ), the resonance measurement method with a cylindrical resonator was employed. The electromagnetic energy absorptance L (attenuation in a bulk absorber with respect to absorber length) was used to compare absorbers of different sizes. Microwave attenuation in the absorber ring located in a resonator of the delay line of the traveling-wave tube model was measured employing a P2-61 panoramic meter for voltage standing wave ratio and attenuation. Experimental values of the real and imaginary ε′′ parts of the complex dielectric constant in pressureless-sintered AlN–SiC composites with different contents and sizes of semiconducting silicon carbide particles are presented. When SiC increases from 20 to 50% in the AlN-based composite, ε′ becomes 1.7–2.1 times higher and ε′′ 5.4–6.8 times higher. The smaller the SiC particles, the greater the increase in ε′ and ε′′, silicon carbide content being the same. The relationship between the thermal conductivity and electromagnetic energy absorptance in the AlN–SiC composites was studied. The range of compromise values was found: they combine relatively high thermal conductivity, 45–55 W/(m · K), and significant absorptance, L = 2.8–3.5 dB/mm, corresponding to the highest silicon carbide content (40–50%) and microsized SiC particles (2.3–4.4 μm). A relationship was established between the imaginarabsorptance L(dB/mm)\( =\sqrt[2]{2.8{\upvarepsilon}^{\prime \prime }} \), allowing the absorptance to be determined from known ε′′ at a frequency of 3.3 GHz.

The microstructural design of composite nanomaterials for microwave sintering using chessboard structurization is proposed. As single-phase and composite nanoparticles and nanofibers are distributed according to the chessboard principle in the mixture and the Si3N4–TiN powder composites acquire a combined microstructure consisting of components that significantly differ in the depth of microwave penetration into the volume, the consolidation process in the electromagnetic microwave field at a ratio of ~50 : 50 can be improved significantly. The effectiveness of the above principle was proved in the production of high-density (~99% relative density) Si3N4–TiN composites and composites reinforced by nanofibers. The chessboard-structured Si3N4–TiN composites were consolidated in a microwave furnace at a frequency of 2.45 GHz in a nitrogen flow at T = 1500°C. In situ mixtures of TiN–40 wt.% Si3N4 and TiN–20 wt.% Si3N4 plasma chemical powders with 7 and 20 wt.% silicon nitride nanofibers incorporated by mechanical mixing and preliminarily coated with titanium nitride were used. Microstructural analysis of the TiN–40 wt.% Si3N4 composite revealed that titanium nitride grains coarsened to 100–200 nm, while silicon nitride grains remained 30–50 nm in size. This indicates that microwave energy is predominantly absorbed by titanium nitride grains, which leads to their self-heating. The mechanical properties of the TiN–40 wt.% Si3N4 nanocomposite were as follows: HV = 21.2 ± ± 0.5 GPa and KIc = 4.9 MPa ⋅ m1/2. Reinforcement of the composites with silicon nitride fibers coated with a titanium nitride layer increased the fracture toughness to 5.5 MPa ⋅ m1/2 at ~ 20 GPa hardness. Increase in the amount of Si3N4 nanofibers from 7 to 20 wt.% did not improve the mechanical characteristics of the composite, indicating that the optimal amount of silicon nitride nanofibers in the composite needs to be determined.

Low-alloy steels prepared by PM methods are widely used in the automotive industry and commercial machinery to manufacture components for actual applications. The unique feature of PM materials is densification through deformation, which significantly enhances the mechanical properties of finished items. Machinability defines the way a material behaves during processing. Surface grinding is one of the traditional finishing processes, which may provide a better surface finish and narrow dimensional tolerance for machined components. The addition of molybdenum to low-alloy steels increases mechanical strength and machinability due to the nature of the alloying element. In this context, current experimental work focuses on the effect of densification on the machinability of the sintered Fe–0.5% C–2% Mo low-alloy steel. One sample was retained in the sintered state for the study, while four others were densified at different levels by uniaxial compaction. In this case, the maximum density of the pre-form was determined by the appearance of lateral cracks on the surface during the application of the incremental axial load for the densification process. Three sintered alloy steel preforms were subjected to cold upsetting by progressively applying three intermediate uniaxial loads. The density of as-sintered and deformed samples was measured according to Archimedes’ principle. The surface grinding was performed on the as-sintered and densified specimens at constant machining parameters. After that, the surface roughness and hardness values were measured. It is found that an increase in density improved surface finish and hardness values of the preforms. The microstructure and surface morphology of the ground samples were also analyzed.

The paper examines variation in the structure and properties of an antifriction composite produced from grinding waste of the R6AM5 high-speed steel with additives of CaF2 solid lubricant depending on the quantitative composition of the main components. The composite is intended to perform in friction units of offset and press cylinders of printing machines that operate in self-lubrication conditions at high rotation speeds (up to 5,000 rpm) and increased loads (up to 5 MPa) in air. The developed production modes allowed the R6AM5 steel grinding waste composite to be appropriately structured. The composite structure is a metal matrix in which CaF2 solid lubricant particles are evenly distributed. The composite’s metal matrix consists of pearlite–carbide and carbonitride phases formed in the presence of R6AM5 steel doping elements. The appropriate amount of the CaF2 solid lubricant, which contributes to reaching the maximum antifriction properties, was determined by a series of experimental mechanical and tribotechnical tests and by fractographic analysis of the materials containing from 3.0 to 10.0 wt.% CaF2. The microstructural, fractographic, mechanical, and tribotechnical tests showed that content of the CaF2 solid lubricant that ensured high mechanical properties and significantly increased the antifriction characteristics of the composites varied from 4.0 to 8.0 wt.% . Electron microscopy studies of the friction surfaces of the R6AM5 + (4.0–8.0)% CaF2 composites confirmed the formation of uniform continuous protective antifriction films that completely covered the contact pair’s friction surfaces and provided self-lubrication. Field tests showed the feasibility of using antifriction bushings made of the new composites produced from R6AM5 steel grinding waste and (4.0−8.0)% CaF2 in the friction units of offset and press cylinders of roll newspaper offset printing machines. The research identified prospects for expanding studies over a wide range of valuable metal waste for the development of new effective antifriction composites with a well-grounded content of components. This would also make another important contribution to protecting the environment against contamination.

Three Ti/TiAl3 microlayer titanium materials, produced by the sintering and rolling of alternating titanium and aluminum ribbons of different thickness at 600, 700, and 770°C, were developed and studied. To prevent oxidation in the sintering and hot rolling processes, an argon-arc-welded stainless-steel container containing a layered workpiece was used for all materials. After hot rolling (one pass), cold rolling was performed to strengthen the titanium bearing layers and reduce the shear strength of the intermetallic layer resulting from the reaction of titanium with aluminum in sintering. The initial thickness of the titanium and aluminum layers was 220 and 50 μm in one case and 100 and 10 μm in the other. Sections and fatigue fractures of the materials were analyzed using photos taken with a scanning electron microscope. The thicknesses of the titanium layers varied from 15 to 28 μm and that of the intermetallic layers from 10 to 22 μm. Fatigue fracture of structural elements in the materials was examined. The intermetallic layer failed by shear in the middle of its thickness. The fractured surface of the samples had steps of approximately the same length and depth. The intermetallic particles were both of equilibrium shape with an average diameter of 2–3 μm and of lamellar shape with a thickness of 0.5–1 μm and a length of 3–5 μm. Testing of the samples with a thickness of 0.25 to 0.5 mm by three-point bending under static load at room temperature revealed that their elastic limit reached 710 MPa and total strain-to-failure was 2.7%. The loading curve showed monotonic increase in the load of the samples to the maximum value and then stepwise decrease and increase in the load associated with subsequent failure of the bearing titanium layers and shear of the intermetallic layers around the failed bearing layers. This resulted in a substantial area under the loading curve, corresponding to the fracture energy of the material.

The effect of plasma spraying parameters on the adhesion and porosity of metal ceramic coatings from clad (Ti, Cr)C–Ni composite powders was studied. The coatings were produced by atmospheric plasma spraying (APS) using a mixture of argon and hydrogen as plasma gases. The arc voltage and current were chosen as variable parameters for controlling the spraying distance and argon flow rate. The 40–80 μm (Ti, Cr)C-based composite powders clad with 17, 25, and 33 wt.% Ni were used to produce the plasma coatings. The microstructure, porosity, and adhesion of the coatings were studied to assess their quality. Optimal plasma spraying modes were determined for each powder. Plasma spraying should be conducted at an electric arc power of 27–29 kW. An increase in the power caused the nickel layer on the (Ti, Cr)C particles to evaporate and degrade, resulting in reduced coating uniformity, increased porosity, and decreased adhesion. The density and adhesive strength of the coatings improved as nickel content of the (Ti, Cr)C–Ni composite power increased from 17 to 33 wt.%. It was found that 17 wt.% Ni in the (Ti, Cr)C–Ni composite powders was not sufficient for producing high-quality plasma coatings. The (Ti, Cr)C–33 wt.% Ni coating had the highest adhesion (38 ± 1.5 MPa) and lowest porosity (7–8%).

Fine gas-atomized powders of R6M5K5 tool steel were studied. The spherical powders were produced with two distinct melting procedures, each involving spraying under different modes: at a conventional pressure of 0.6 MPa used to make powders of this steel and a calculated pressure of 2 MPa. To obtain a fine-sized fraction, the powders were sieved through a wire mesh with 50 μm square openings, and the content of this fraction was calculated for each of the two powders. The powders with particle sizes greater than 50 μm were subsequently ground and additionally sieved through a 50 μm mesh. Four types of powders with particle sizes below 50 μm were produced using this method. They varied in particle size distribution and particle shape. Mechanical tests were performed with the powders of this size fraction. The equivalent particle diameter distribution, morphology, and changes in elemental composition of the powders were studied. Distribution characteristics, including d10, d50, and d90, were calculated. The arithmetic mean of flat particle projections was slightly higher for the powder atomized employing the conventional mode (0.6 MPa), measuring 0.914 compared to 0.901 for the powder particles atomized under the calculated mode. The yield of the <50 μm fraction was lower (6 and 55 wt.%, respectively). After grinding, the roundness of both powders decreased, resulting in more complex shapes. The relative bulk density, relative tapped density, and flowability of the powders decreased as the roundness factor reduced. An attempt to classify the tool steel powders using the Hausner ratio and Carr index, commonly applied to pharmaceuticals and some metal powders to evaluate their flowability, indicated that the potential application of this classification required further verification. The flowability of the studied powders correlated well with the magnitude of the repose angle.

Near-infrared long afterglow materials have the characteristics of non-obscuring bio autofluorescence and good photo/chemical stability. They can play an essential role in bioimaging, whereas LiGa5O8:Cr3+ has long afterglow and optical photoexcitation properties. In this paper, LiGa5O8:Cr3+ nanophosphors were successfully synthesized by hydrothermal method. X-ray diffraction (XRD) patterns were recorded using an X-ray diffractometer. Luminescence spectra and decay curves were obtained via a fluorescence spectrophotometer. The microstructural properties of the samples were analyzed using scanning electron microscopy (SEM). Transmission electron microscopy (TEM) images were recorded on a TEM instrument. Thermoluminescence spectrometer was employed to obtain a thermoluminescence curve. Using Tween 20 as the experimental chelating agent, it was found that the ratio of total metal ions to Tween 20 significantly affected the luminescence properties of LiGa5O8:Cr3+. When the ratio of total metal ions to Tween 20 was 7 : 1, the sample had less impurity phase, high crystallinity, regular grain shape, and a size of about 100 nm. The fluorescence spectra showed that the main excitation peaks were 410 nm and 608 nm, and the main emission peaks were 720 nm. The sample with a ratio of 7 : 1 had a higher relative intensity than all other samples, with more effective traps and greater stored energy to produce more luminescent carriers. The kinetic order at this point was 2. It provides a solid basis for bioimaging.

The general chemical and phase composition of the ilmenite concentrate from the Irshansk deposit was determined. The content of titanium (in terms of TiO2) in this concentrate was more than 50 wt.%. Ilmenite was the main phase component, which partially turned into pseudorutile through secondary processes. The concentrate was oxidized using microwave heating. Prior to microwave heating, particles of the starting ilmenite concentrate were ground for 3 min in a planetary-ball mill to an average size of 10 μm. A 100 g sample of the ground concentrate was heated for 30, 60, 90, and 120 min. In the heating for 30 min, pseudorutile disintegrated and pseudobrookite formed. Subsequent heating for 60 and 90 min led to the formation of rutile and increased the amount of pseudobrookite. Microwave heating for 120 min resulted in the complete decomposition of ilmenite. Pseudobrookite, rutile, and quartz were identified in an averaged sample by X-ray diffraction. Iron oxides were not found in the averaged sample. Interaction of the ilmenite concentrate sample with air during heating led to intensive surface oxidation of the material to form a larger amount of rutile and to release of iron oxide from the pseudobrookite as hematite. Electron microscopy of the oxidized particles revealed that titanium was mainly contained in fine concentrate subparticles up to 1 μm in size, and impurities (silicon and aluminum compounds) formed coarser agglomerates. The sizes of ore macroparticles hardly changed after microwave heating. Comparison of the effects from microwave and conventional heating on the ilmenite concentrate showed that heating in a resistance furnace for 120 min did not result in complete oxidation of ilmenite even at higher temperatures. Additional grinding of the starting ilmenite concentrate increased the heating and oxidation temperatures of the material subjected to microwave processing.

In this study, new biodegradable magnesium composites Mg–1Ca–1Y–xSr (x = 0.5, 1.0, 1.5, and 2.0) were designed and produced by mechanical alloying to improve the corrosion properties. X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) were employed to characterize the resulting biodegradable magnesium composites. Besides, the corrosion process was monitored with the help of electrochemical corrosion testing methods, such as open circuit potential (OCP), anodic polarization, and electrochemical impedance spectroscopy (EIS). The results showed that the microstructure of the composites consisted of different phases, with their amounts increasing when adding Sr. Moreover, the phase analysis revealed the formation of intermetallic phases Mg2Ca, Mg17Sr2, and Mg24Y5 in the composites. The immersion of composites in 0.9 wt.% NaCl solution exhibited cathodic potential after 2 h. Enhanced corrosion potential was obtained for a 2.0 wt.% Sr composite. In contrast, composite A with the lowest Sr content exhibited higher cathodic corrosion potential. Analysis of the anodic curves revealed passivation behavior for all composites after immersion into the solution. In addition, pitting was observed on the sample's surface, and the potential for pitting increased for the Mg–1Ca–1Y composite. On the other hand, a semi-circle capacitive loop was noted for all composites, and polarization resistance of the film was better for Mg–1Ca–1Y–2Sr than other samples. That is probably due to the involvement of Sr in the protective oxide layer and the decrease of the galvanic effect in the microstructure. In general, the addition of Sr was favorable for the new biodegradable Mg–1Ca–1Y composite, which may be considered a promising candidate for biodegradable magnesium implants.

Changes in the porous structure of compacts produced from carbonyl iron and a mixture of iron with doping additions (4 wt.%) with increasing holding time at 900°C were analyzed. The compacts were sintered in a hydrogen atmosphere for 5, 10, 15, and 30 min. Powders of carbonyl iron, nickel, and ferroalloys (Fe–Si, Fe–Cr, Fe–Mo) were the starting materials. The structural parameters (characteristic pore size and radius of conditional particles) were evaluated from computer processing of electron microscopy images. The experimental studies found that the average characteristic pore size in the samples of carbonyl iron and those with doping additions changed differently during sintering, especially in the first minutes. The carbonyl iron samples had 2% higher porosity than that of the doped ones after 5 min of sintering but became 9.5% lower after 15 min. This can be explained by a significant change in the interaction between pores in the homogenization process in the samples with doping additions at the beginning of sintering. A stage with uneven pore filling resulting from local chemical inhomogeneity was revealed. To describe the metal component of the porous structure, the radius of conditional particles was chosen. This parameter increased 4.7 times faster for pure carbonyl iron than for doped carbonyl iron during sintering. The experimental studies showed that the relationship between the radius of conditional particles and the porosity of the samples was hyperbolic and determined by the size of the starting powders. The coefficients of this relationship, experimentally found for a material of specific chemical composition, can be used to describe the sintering of materials with similar chemical compositions.

Scanning electron microscopy and X-ray energy-dispersive spectroscopy were employed to study the sintering of powders from the induction-melted industrial ferromagnetic Sm2(Co,Fe,Zr,Cu)17 alloy by the hydrogenation, disproportionation (HD), desorption, recombination (DR) (HDDR) route. The HD stage proceeded at 700°C and DR at 950°C. The experimental results showed that sintering of the powders occurred at the HD stage to produce a mechanically integral highly porous material. The porosity of the sintered materials was found to decrease as the compaction pressure and powder particle refinement increased. The powder compaction pressure was estimated to range from 2 to 5 t/cm2. The decrease in sintering temperature was attributed to the higher diffusion rate of the alloy components resulting from the decrease in particle size, hydrogen-initiated phase transformations, and the hydrogen solid solution present in the alloy. Phase transformations occurred when the pressure changed at high temperatures. If the hydrogen pressure was high, the intermetallic was not thermodynamically stable and disintegrated (disproportionated) into several phases. If the hydrogen pressure was low (vacuum), the rare earth metal hydride was thermodynamically unstable and disintegrated, while the rare earth metal interacted with other phases to form the starting intermetallic. These phenomena are due to chemical reactions within a solid body, proceeding through the diffusion of components. The new sintering method for ferromagnetic materials has process advantages over existing methods: it does not require holding at the highest heating temperatures or usage of complex dies or complex equipment and results in the production of anisotropic nanostructured materials. Ways to improve the properties of sintered materials at low temperatures (in particular, increasing the homogeneity of their microstructure and decreasing the porosity) are proposed, such as optimization of sintering parameters and homogenization of the powders by particle size.

The reactive synthesis of heterophase refractory ultrahard B4C-based composites by spark plasma sintering (SPS) was examined. To produce heterophase B4C + TiB2 + CrB2 ceramics, the chemical reaction between boron carbide and chromium oxide and between boron carbide and titanium carbide resulting in boron carbide–chromium diboride and boron carbide–titanium diboride composites was previously studied. The reactive sintering of B4C + Cr2O3 + C and B4C + TiC mixtures using boron carbide powders obtained from the Zaporizhzhya Abrasive Plant and Donetsk Chemical Reagent Plant (Ukraine) was compared. The boron carbide powders differed in the ratio of B13C2 and B4C phases and particle sizes. The reactively synthesized TiB2, CrB2, and CrTiB2 boride phases positively influenced the SPS consolidation and properties of the boron carbide composites. The B4C–CrB2 and B4C–TiB2 ceramics subjected to Vickers hardness testing under a load of 98 N showed HV levels of 23–29 GPa and 26–28 GPa. The ceramics demonstrated brittle fracture according to the Half-penny model, with a fracture toughness of 3 MPa∙m1/2 for B4C–CrB2 and 4.4 MPa∙m1/2 for B4C–TiB2. The 90 vol.% B4C–5.5 vol.% TiCrB2–4.5 vol.% C ceramics with ~33 GPa hardness and ~ 4 MPa∙m1/2 fracture toughness were produced by reactive SPS from a mixture of B4C (Zaporizhzhya Abrasive Plant), 6.6 wt.% TiC, and 11 wt.% Cr2O3. The high strength of TiCrB2 ceramics was attributed to the stress–strain state, where the matrix phase of boron carbide was subjected to compressive stresses. The high hardness and fracture toughness allow the B4C–TiCrB2 composite to be classified as an ultrahard ceramic material.

The effect of niobium on the structure, phase composition, and mechanical properties of γ -TiAl alloys were studied. The γ-TiAl alloys were doped with niobium within a solid solution; the amount of niobium in the alloys ranged from 2 to 10 at.%. Niobium was introduced as an Al3Nb intermetallic, allowing a superfine powder mixture to be produced by high-energy grinding. A TiH2 + Al3Ti + Al3Nb powder mixture was used to prepare the γ -TiAl alloys. This route minimized the Kirkendall–Frenkel effect in the Ti–Al system and prevented increase in additional porosity during sintering. Only TiAl and Ti3Al phases were revealed in the sintered materials, indicating that niobium had dissolved in the existing phases. To achieve the desired phase composition in the alloy, the content of aluminum had to be increased to compensate for its partial loss through evaporation during sintering. The alloys with a lower aluminum content showed higher strength but lower ductility, both at room and elevated temperatures, because of a greater amount of the α2 phase. Niobium doping reduced sintering shrinkage by 2–4% and inhibited the grain growth. The material with a low niobium content had greater strength and ductility at a sintering temperature of 1200°C, when the grain size hardly changed. The grain growth was inhibited by niobium doping at a high sintering temperature of 1400°C. The yield stress increased with the niobium content. The studied alloys exhibited satisfactory low-temperature strength and ductility, as well as high creep resistance at 700°C. They showed a little tendency to weakening and are therefore promising for hightemperature applications above 700°C.

Magnesium alloys are widely used in the engineering and medical sectors due to their unique characteristics. Thus, their Young’s moduli are equivalent to that of human bone. Along with other properties such as their lightweight and biodegradable nature, these alloys attract material scientists for applications in the medical field. The pure Mg alloy is very reactive towards different chemicals, exhibiting low corrosion resistance. However, enhancing the corrosion resistance requires a mandatory addition of some reinforcements. Besides, it was identified that the nanocomposite materials consistently outperform other materials. Therefore, the present work studies different Mg-based nanocomposites according to the reinforcing elements, application challenges, and prospects. The effect of adding zinc, zirconium, calcium, strontium, and other rare earth elements (REEs) is also under discussion. These elements are selected depending upon their nature, i.e., these materials’ influence on the human body. The effects of REEs after their introduction into Mg-based alloys in terms of biocompatibility, mechanical properties, and corrosion performance are considered. Besides, consideration was also given to the influence of ternary elements on the Mg-based nanocomposites. Mechanical strength and corrosion behavior of composites in body fluid assume numerous challenges. The corrosion and mechanical characteristics of ternary and quaternary alloys remain poorly explored. These challenges are also discussed in detail, along with the application prospects of Mg-based nanocomposites.

The mechanical properties of lattice structures with 78–79% pore volume produced from iron powders by selective laser melting were studied. As the mechanical properties of lattice structures can be predicted from the topology and dimensions of the unit cell, the influence of spatial orientation of the unit cells on the mechanism whereby the samples are deformed should be also established. Three types of lattice structures with different spatial orientation of unit cells represented by simple cubic volumes of porous material with the same size of lattice and unit cell generatrixes were considered. The response of the lattice structure to different types of loads was analyzed. Measurements of the elastic modulus in four-point bending tests showed that porous 3D lattices with different unit cells had an elastic modulus of the same order, from 17.2 to 23.9 GPa. Compression tests of the 3D lattice structures indicated that the lattices located at an angle of 45° to the z axis deformed according to similar patterns and had almost the same yield stress (14.0–15.4 MPa). The highest yield stress (40.5 ± 3.3 MPa) was observed in the lattices whose unit cells were parallel to the x, y, and z axes, which is due to the layered deformation of the cells. The greatest impact toughness (22.1–23.2 J/cm2), as well as the compressive yield stress and elastic modulus, was also shown by these lattices. Analysis of the fracture structure of the samples after impact toughness tests indicated that the iron lattice structures of all three types had pit microrelief characteristic of viscous fracture. The results demonstrated the prospects of applying additive manufacturing techniques for the development of iron-based powder materials by selective laser melting to form a lattice structure with highly reproducible mechanical characteristics.

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.