X-ray Diffraction Phase Research Articles

Influence of complex flotation reagents on flotation effect of low-rank coal and mechanism analysis

ABSTRACT This study investigates the surface characteristics of Yongshengyuan (YSY) low-rank coal, a material known for its flotation challenges, employing a suite of analytical techniques such as Zeta potential analysis, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction phase analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The flotation performance of low-rank coal was evaluated using three distinct surfactants (sodium petroleum sulfonate, hexadecyl dimethyl ammonium bromide, methyl oleate) in conjunction with 3# oil (base oil). The experimental results demonstrate that all surfactants enhance the flotation efficiency of low-rank coal, with the combination of sodium petroleum sulfonate and methyl oleate with 3# oil proving most effective. Comprehensive analyses of AFM, Zeta potential, contact angle and wetting heat of coal sample pre and post-application of the compound reagent, reveal that the surfactant preferentially interacts with the polar hydrophilic sites on the YSY low-rank coal surface. This interaction diminishes the presence of oxygen-containing functional groups on the coal surface, increases the ratio of hydrophobic groups, enhances the coal’s hydrophobicity, and consequently bolsters the flotation efficiency of the low-rank coal.

X-ray phase contrast imaging and diffraction in the laser-heated diamond anvil cell: A case study on the high-pressure melting of Pt

X-ray phase contrast imaging and diffraction in the laser-heated diamond anvil cell: A case study on the high-pressure melting of Pt

Impact of sintering temperature and KMnO4 addition on the growth of Bi2212 ceramics

In this study, the highest volume fraction was obtained by the combined effect of KMnO4 doping and different sintering temperatures (840 and 850 °C). Bi2Sr2CaCu2(KMnO4)xO8+δ compounds with x = 0, 0.01, 0.03, 0.05 and 0.07 were prepared by the conventional solid-state reaction method. The phase composition and microstructure were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and Raman Spectroscopy. The XRD phase study showed that the optimum sintering temperature was 850 °C with a KMnO4 doping concentration of 0.05. With increased doping (x), the texture of Bi2212 became more crystalline, with a grain growth preference along the (00l) direction. It is clear that the rate of formation of the Bi2212 phase is favored by high sintering temperature and addition of KMnO4. The line intensities of the Bi-2212 phase were found to increase significantly with KMnO4 addition up to the critical value of x = 0.01 and the cell structure volume is seen to decrease with increasing doping rate. This may be attributed to inhomogeneities in oxygen concentration This indicates that the sintering temperature has a strong influence on the structural and morphological properties. As reported in the literature, the Raman modes at 489.76 cm-1 and 630 cm-1 are associated with the vibrations of O(3)BiA1g and O(2)SrA1g along the c axis for the Bi-2212 phase. The A1g modes are symmetric for vibrations of Bi, Sr, Ca, Cu, OBi, OSr and OCu along the c axis.

Reentrant polar phase induced by the ferroionic coupling in Bi1−xSmxFeO3 nanoparticles

Using the model of four sublattices, the Landau-Ginzburg-Devonshire-Kittel phenomenological approach and the Stephenson-Highland ionic adsorption model for the description of coupled polar and antipolar long-range orders in ferroics, we analytically calculated the phase diagrams and polar properties of Bi1−xSmxFeO3 nanoparticles covered by surface ions with dependence on their size, surface ions density, samarium content x, and temperature. The size effects and ferroionic coupling govern the appearance and stability conditions of the long-range ordered ferroelectric, reentrant ferrielectric, and antiferroelectric phases in Bi1−xSmxFeO3 nanoparticles. Calculated phase diagrams are in qualitative agreement with the x-ray diffraction phase analysis, electron paramagnetic resonance, infrared spectroscopy, and electrophysical measurements of Bi1−xSmxFeO3 nanopowders sintered by the solution combustion method. The combined theoretical-experimental approach allows us to explain the influence of the ferroionic coupling and size effects in Bi1−xSmxFeO3 nanoparticles on their polar properties. Published by the American Physical Society 2024

Influence of Graphene Oxide on Printability, Rheological and Mechanical Properties of Highly Filled Alumina Filaments and Sintered Parts Produced by FFF

The aim of the study was to investigate the effect of the addition of graphene oxide (GO) on the rheological and mechanical properties of extruded polyamide 12 (PA12) filaments with high aluminum oxide (Al2O3) content used for 3D printing using the fused filament fabrication (FFF) method. Firstly, Al2O3-based mixtures with 0.10, 0.25 and 0.50 vol.% GO content were prepared. These mixtures were dried and subsequently combined with paraffin wax (PW), stearic acid (SA) and polyamide 12 (PA12) in an organic solvent. After drying in a vacuum oven and sifting, powder compositions of 74 wt.% (Al2O3 + GO)/26 wt.% (PA12 + PW + SA) with different GO content were obtained. All compositions were successfully extruded into filaments for 3D printing. Rheological, microstructural and mechanical studies of the compositions and filaments were carried out. X-ray diffraction phase analysis and Raman spectroscopy were also performed. It was shown that 0.10 and 0.25% vol. GO proved to be a universal additive that resulted in an increase in the rheological and mechanical properties of the highly filled polymer and also improved its 3D printability, which ultimately helped obtain a ceramic product with complex shape using the FFF method.

Anomalous release of indoles from amorphous solid dispersion formed with a polymeric network

AbstractAmorphous solid dispersion (ASDs) is a technique used in the pharmaceutical industry to enhance the solubility, dissolution rate, and bioavailability of poorly soluble drugs. Polymeric materials, and recently polymer gels form and stabilize the amorphous structure by inhibiting the aggregation/precipitation of such drugs. In this work indole, 5-aminoindole and 5-hydroxyindole loaded poly (N-isopropylacrylamide) (PNIPA) hydrogels were studied. Swelling and uptake measurements, X-ray diffraction (XRD), liquid and solid phase nuclear magnetic spectroscopy (NMR) and high sensitivity differential scanning calorimetry (DSC) were applied to understand the drug – matrix interactions affecting the release. We confirmed that the hydrogel fostered the fine uniform distribution of the hydrophobic probe molecules and successfully prevented any crystalline or amorphous phase formation during water removal, leading to a glassy solution, a special form of ASD. Despite the limited difference between their chemical composition the probe molecules showed dissimilar drug release behavior from dried loaded gel disks. While Nuclear Overhauser Enhancement Spectroscopy (NOESY) measurements revealed a “bidental” interaction between 5-hydroxiindole and the polymer, no localized interactions were found for indole. The release of the bidentally linked derivatives is rapid and complete: they act as molecular spacers, promoting the rehydration of the chains. In contrast, part of the indole remains irreversibly trapped being confined between the chains without any orientation, shedding light on the role of the steric consequences of the interaction. Our findings also indicate that such drug delivery compositions should be treated as ternary systems (carrier + drug + liquid) already in the design stages of drug release systems.

Preparation Method of a Metal Carrier for a Catalyst for the Recovery of Exhaust Gases from Nitrogen Oxides

The article shows the process of preparing an oxide layer on the surface of titanium for use in industrial catalysis. Data from physical and chemical studies are presented, namely microhardness, porosity, thickness, specific surface area, adhesion and thermal stability of the active layer.To determine the physicochemical characteristics of the resulting oxide layer, the following analysis methods were used: X-ray diffraction analysis (XRD), X-ray diffraction phase analysis (XPA), X-ray absorption analysis (XRA), and X-ray fluorescence analysis. The thickness of the oxide layer depending on the duration of anodization was estimated by optical microscopy.

Новый катодный материал La2/3Cu3Ti4−xFex O12−δ для твердооксидного топливного элемента: синтез и электропроводность

Copper lanthanum titanate La2/3Cu3Ti4−xFexO12−δ x = 0–1 was doped with Fe3+ cations. The diagram of the dependence of the tolerance factor on the relative electronegativity of cations for all studied compositions was represented. It was shown that all the compositions exist in the region of existence of distorted perovskite. X-ray diffraction and X-ray phase analysis methods established the region of existence of solid solutions of La2/3Cu3Ti4−xFexO12−δ obtained by ceramic technology, which was 0 ⩽ x ⩽ 0.4. The temperature dependences of electrical conductivity for the compositions from the region of existence of solid solutions La2/3Cu3Ti4−xFexO12−δ were obtained. The ionic-electronic nature of conductivity was suggested. It was shown that the decrease of electronic conductivity under the increase of iron content was due to the compensation of electronic carriers formed during acceptor doping.

Влияние технологических параметров на микроструктуру и свойства сплава AlSiMg, полученного методом селективного лазерного плавления

Introduction. The development of additive technologies is aimed at the synthesis of new powder compositions for selective laser melting plants, the study of the effect of mode parameters on the stable quality of products. The purpose of this work is to study the effect of the scanning strategy on the microstructure, elemental composition, porosity and density of specimens obtained by selective laser melting from non-spherical powders (Al — 91 wt. %, Si — 8 wt. %, Mg — 1 wt. %), subjected to special preparation to determine the optimal conditions for selective laser melting. The research methods are methods of X-ray diffraction and X-ray phase analysis, transmission electron microscopy. The paper examines specimens formed using four different scanning strategies. Results and discussions. A promising aluminum alloy AlSi8Mg is developed for selective laser melting. The material has good manufacturability and low powder cost. The technological parameters of melting make it possible to form a thin structure with a low level of porosity. The mechanism of influence of the scanning strategy on porosity, surface morphology, relative density and microstructure is investigated. A specimen from the AlSi8Mg powder composition with a high relative density of 99.97 % is produced by selective laser melting with an energy density of 200 J/mm3, a specimen scanning circuit when the direction of laser movement changes by an angle of 90° each odd layer. It is proved that the density of the AlSiMg alloy depends on the scanning strategy used. The calculated density of the specimen was 2.5 g/cm3, which corresponds to the density of silumin. Analysis of SEM images and maps of the distribution of elements (Al, Mg, Si) of the specimens showed that different specimen formation strategies do not affect the nature of silicon distribution. A unique grain structure is observed in the resulting AlSi8Mg alloy. The melt pool consists of small grains along the border and large grains in the center. The formation of fine grains is explained by the addition of Si and the high cooling rate during selective laser melting.

Quaternary Zinc Alloys with Magnesium, Calcium and Strontium after Hydrostatic Extrusion-Microstructure and Its Impact on Mechanical and Corrosion Properties.

The development of bioabsorbable implants from Zn alloys is one of the main interests in the new generation of biomaterials. The main drawbacks of Zn-based materials are their insufficient mechanical properties. In the presented studies, a quaternary alloy composed of zinc with magnesium (0.2-1 wt. %), calcium (0.1-0.5 wt. %) and strontium (0.05-0.5 wt. %) was prepared by gravity casting followed by hot extrusion and then by hydrostatic extrusion. Microstructural characterization using scanning electron microscopy (SEM) and X-ray diffraction (XRD) phase analysis was performed. The mechanical properties were examined, using static tensile tests. Corrosion properties were analyzed using immersion tests. Samples were immersed in Hanks' solution (temperature = 37 °C, pH = 7.4) for 14 days. All alloys were subjected after corrosion to SEM observations on the surface and cross-section. The corrosion rate was also calculated. The microstructure of the investigated quaternary alloy consists of the α-Zn grains and intermetallic phases Mg2Zn11, CaZn13 and SrZn13 with different grain sizes and distribution, which impacted both mechanical and corrosion properties. Thanks to the alloying by the addition of Mg, Ca, and Sr and plastic deformation using hydrostatic extrusion, outstanding mechanical properties were obtained along with improvement in uniformity of corrosion rate.

Synthesis of biocompatible Ti-6Al-4V composite reinforced with ZrO2 and bioceramic produced by powder metallurgy: Morphological, structural, and biocompatibility analysis.

In this experimental study, the initial phase involved preparing composite structures with various mix ratios using the Ti-6Al-4V alloy, widely used in clinical applications, in conjunction with ZrO2 and hydroxyapatite (HA) synthesized via the precipitation method, employing powder metallurgy techniques. Subsequently, the microstructures of the resultant hybrid composite materials were imaged, and x-ray diffraction (XRD) phase analyses were conducted. In the final phase of the experimental work, tests were performed to determine the biocompatibility properties of the hybrid composites. For this purpose, cytotoxicity and genotoxicity assays were carried out. The tests and examinations revealed that structures compatible both morphologically and elementally were obtained with no phase transformations that could disrupt the structure. The incorporation of ZrO2 into the Ti-6Al-4V alloy was observed to enhance cell viability values. The value of 98.25 ± 0.42 obtained by adding 20% ZrO2 gave the highest cell viability result. The addition of HA into the hybrid structures further increased the cell viability values by approximately 10%. All viability values for both HA-added and HA-free groups were obtained above the 70% viability level defined in the standard. According to the genotoxicity test results, the highest cytokinesis-block proliferation index values were obtained as 1.666 and 0.620 in structures containing 20% ZrO2 and 10% ZrO2 + 10% HA, respectively. Remarkably, all fabricated composite and hybrid composite materials surpassed established biocompatibility standards and exhibited nontoxic and nongenotoxic properties. This comprehensive study contributes vital insights for future biomechanical and other in vitro and in vivo experiments, as it meticulously addresses fundamental characterization parameters crucial for medical device development. RESEARCH HIGHLIGHTS: Support of optimum doping rates ions on hybrid composites and concentrations. Development of uniform surface appearance and distributions/orientations of microcrystals on ceramic compounds Improvement of cell viability and desired increase in biocompatibility with the doping of HA.

Selection of heat treatment and its impact on the structure and properties of AK10M2N–10%TiC composite material obtained via SHS method in the melt

The composite materials based on the Al–Si system alloys, strengthened with a highly dispersed titanium carbide phase, possess improved characteristics and belong to the group of promising structural materials. Currently, self-propagating high-temperature synthesis (SHS) based on the exothermic interaction, wherein titanium and carbon precursors directly involve in the melt, is the most accessible and effective method to obtain them. This paper proves the feasibility and demonstrates the successful synthesis of a 10 wt.% titanium carbide phase in the melt of the AK10M2N alloy, resulting in the AK10M2H-10% TiC composite material. Samples of the matrix alloy and the composite material were subjected to heat treatment according to the T6 mode, with various temperature-time parameters for hardening and aging operations. Based on the results, optimal heat treatment modes were selected to ensure maximum hardness. We studied the macroand microstructure of the obtained samples and performed micro X-ray spectral and X-ray diffraction phase analyses. Different groups of properties underwent comparative tests. It was established that the density of AK10M2N–10%TiC samples before and after heat treatment, according to optimal modes, is close to the calculated value. We showed that the combination of reinforcement and heat treatment significantly increases hardness, microhardness, and compressive strength, with a slight decrease in ductility. Additionally, it maintains the values of the coefficient of thermal linear expansion, high-temperature strength, and resistance to carbon dioxide and hydrogen sulfide corrosion at the level of the original alloy. The greatest effect was observed during the investigation of tribological characteristics: heat treatment of the composite material according to the recommended mode significantly reduces the wear rate and friction coefficient, eliminates seizure and tearing, and prevents temperature rise due to friction heating.

Exploring 2D X-ray diffraction phase fraction analysis with convolutional neural networks: Insights from kinematic-diffraction simulations

Deep-learning models are effective for analyzing the complex information in 2D X-ray diffraction (XRD) patterns. Accurately collecting parameters of the material sample is crucial during model training, significantly impacting model performance. In this study, we employ a kinematic-diffraction simulator to generate simulated 2D XRD patterns for Ti–6Al–4V alloy, allowing precise control of sample parameters. These simulated patterns are used to train convolutional neural networks, predicting β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upbeta$$\\end{document}-phase volume fractions. The training data set consists exclusively of 2D XRD patterns with pure α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upalpha$$\\end{document}- or pure β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upbeta$$\\end{document}-phase, while the testing set incorporates patterns with intermediate phase volume fraction. In particular, we investigate how the architectures of the model influence prediction reliability and computational performance. Experimental results reveal that, with appropriate training, the convolutional neural network accurately detects intermediate phase volume fractions even trained with only pure-phase patterns, achieving a mean square error accuracy of 9.4×10-4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9.4 \ imes 10^{-4}$$\\end{document}.Graphical abstract

Thermal-induced evolution of microstructure as a plasma arc coating Direction-Dependent phenomenon

This study elucidates the effects of different directed energy deposition trajectories on the microstructure and properties of powder plasma transferred arc welding (PPTAW) fabricated coatings. Two trajectories, straight (STT) and complex (CXT), were explored to deposit NiCrBSi powders onto a low alloy steel substrate. Finite element thermal analysis revealed distinct heat distribution zones, the middle zone (MZ) and transition zone (TZ), showing temperature variations between the STT and CXT coatings. Microstructural examination indicated lower dendrite arm spacing (DAS) in the STT coating (11 μm) than in the CXT coating (16 μm). Electron backscatter diffraction (EBSD) analysis demonstrated significant grain refinement in the STT coating (17.4 μm) versus the CXT coating (68.7 μm). X-ray diffraction phase analysis identified three reinforcing phases − γ-Ni, Cr23C6, and Cr3C2 – enhancing corrosion resistance and tribological properties. The STT coating exhibited superior corrosion resistance with a corrosion current density (icorr) of 12.8 µA/cm2, while the CXT coating showed icorr of 34.3 µA/cm2. Additionally, the STT coating exhibited higher hardness (832 ± 33 HV1.0) and better wear resistance with a wear rate of 10.46 ± 0.29 × 10-3 m3/m, over the CXT coating (hardness: 450 ± 36 HV1.0; wear rate: 12.67 ± 0.54 × 10-3 m3/m).

Оптимизация режимов селективного лазерного плавления порошковой композиции системы AlSiMg

Introduction. New aluminum-based powder systems are currently being developed for additive manufacturing. The scientists' work is aimed at comprehensive studies of powder production, optimization of conditions for alloy production and formation of three-dimensional specimens with minimal porosity and absence of cracking during selective laser melting. The purpose of this work is the synthesis of an almost spherical Al-Si-Mg composite powder (91 wt. % Al, 8 wt. % Si, 1 wt. % Mg) from aluminum powder PA-4 (GOST 6058-22), silicon powder (GOST 2169-69) and magnesium powder MPF-4 (GOST 6001-79), which were not originally intended for selective laser melting technology. The work also provides for the optimization of selective laser melting modes to obtain an alloy and form three-dimensional specimens with minimal porosity and no cracking. To create a powder composition, powders ranging in size from 20 to 64 μm were selected by sieve analysis and subjected to mechanical mixing in a ball mill in a protective argon medium for one hour. The research methods are methods of X-ray diffraction and X-ray phase analysis, transmission electron microscopy, mechanical tests of microhardness. Studies of the powder composition after mechanical mixing showed that the mixed powder of aluminum, silicon and magnesium is a conglomerate of particles of spherical, oval and irregular shape. Results and discussions. The optimal modes for obtaining a specimen with a minimum porosity of 0.03 % and a microhardness of 1,291 MPa are selective laser melting modes: P = 90 W, V = 225 mm/s, S = 0.08 mm, h = 0.025 mm. The conducted research shows the possibility of synthesizing products from metal powders that are not adapted to processing by selective laser melting and obtaining an alloy with new mechanical properties during laser action.

Comparative Evaluation of Titanium Feedstock Powder Derived from Recycled Battlefield Scrap vs. Virgin Powder for Cold Spray Processing.

Gas-atomization is extensively used to produce metallic feedstock powders for additive manufacturing processes, including gas dynamic cold spray processing. This work explores the potential utility of on-demand recycled titanium scrap feedstock powder as a viable substitute for virgin powder sources. Three recycled titanium powders were atomized from different battlefield scrap sources using a mobile foundry developed by MolyWorks Materials Corporation. Recycled titanium alloy powders were compared against virgin Ti-6Al-4V powder to verify there were no significant variations between the recycled and virgin materials. Powder characterization methods included chemical analysis, particle size distribution analysis, scanning electron microscopy (SEM), Karl Fischer (KF) titration moisture content analysis, X-ray diffraction (XRD) phase analysis, microparticle compression testing (MCT), and nanoindentation. Results indicate that recycled titanium powder provides a viable alternative to virgin titanium alloy powders without compromising mechanical capabilities, microstructural features, or ASTM-specified composition and impurity standards. The results of this work will be used to aid future research efforts that will focus on optimizing cold spray parameters to maximize coating density, mechanical strength, and hardness of recycled titanium feedstock powders. "Cold spray" presents opportunities to enhance the sustainability of titanium component production through the utilization of recycled feedstock powder, mitigating issues of long lead times and high waste associated with the use of conventional virgin feedstock.

Enhancement of biohydrogen production by photo-fermentation of corn stover via visible light catalyzed titanium dioxide/activated carbon fiber

In this study, titanium dioxide/activated carbon fiber (TiO2/ACF) was synthesized by liquid-phase deposition method and the effect of TiO2/ACF on the performance of photo-fermentation biohydrogen production (PFHP) from corn stover under visible light catalysis was discussed. Results show the maximum cumulative hydrogen yield (CHY) obtained under the optimal conditions was 74.0 ± 1.3 mL/g TS with TiO2/ACF addition of 100 mg/L, which was twice that without TiO2/ACF addition (36.9 ± 1.0 mL/g TS). Initial pH value had the most significant effect on CHY. The addition of TiO2/ACF promoted the metabolic pathway of nitrogenase to reduce H+ produced by consuming acetic acid and butyric acid to hydrogen, and also shortened the photo-fermentation period. By scanning electron microscopy and X-ray diffraction analysis, the morphology and phase structure of TiO2/ACF after PFHP did not change significantly. This study laid the foundation for the reuse of TiO2 and its practical application in PFHP.

Spontaneous room temperature reaction of titanium and its alloys with hydrogen during self-shearing reactive milling

Surface wear-activated spontaneous reactions of titanium and its alloys with hydrogen at room temperature are shown in this work. Titanium powder, intensively mixed under hydrogen pressure in a planetary mill, without any grinding media, reacts readily with hydrogen gas with the formation of stoichiometric titanium dihydride. The reaction, once initiated, proceeds spontaneously even without movement of the milling vial with a similar reaction rate. The moment of initiation of the reaction seems to be related to the removal of oxide impurities from the surface of the titanium particles and is strongly correlated with milling velocity. According to thermogravimetric measurements and X-ray diffraction (XRD) phase analysis, titanium is fully converted to TiH2. Titanium alloys were found to react in the same manner. Ti-5553 (β) reacts more easily than grade 5 Ti (Ti-Gd5) (α’), which is more reactive than grade 2 Ti (Ti-Gd2). The titanium alloy particles maintain their shape and coherency after hydrogenation. The method seems to be extremely cost-effective in the synthesis of titanium hydride and also allows the production of hydrogenated alloyed powders in spherical form, which can potentially be applied in the additive manufacturing of titanium foams. The results also show a significant risk of using titanium alloys in a hydrogen atmosphere at room temperature. It seems that after losing the protective oxide layer, parts made of pure titanium or its alloys may undergo catastrophic destruction after losing strength and ductility upon full conversion to hydride.

Электроискровое модифицирование поверхности аддитивного сплава ВТ6 высокоэнтропийным и аморфным электродами

Unsatisfactory quality of the surface layer of additive products, in particular increased surface roughness, prevents the widespread use of electron beam powder bed fusion (EBPBF). Electrospark treatment (EST) is one of the methods for smoothing and hardening the surface layer. The work shows the possibility of modifying the surface of additive VT6 alloy samples by reactive EST with multicomponent electrodes. For this purpose, the authors used electrodes made of the Fe48Cr15Mo14Y2C15B6 bulk metallic glass forming alloy and the FeCoCrNi2 high-entropy alloy. Based on the results of scanning electron microscopy, it was identified that after EST, both modified layers have a thickness of about 16 μm. X-ray diffraction phase analysis showed that in the case of treatment with an amorphous electrode they contain carboborides of the Ti(B,C) type, and in the case of treatment with a high-entropy electrode – intermetallic of the Ti2(Fe,Ni) type. The modified layers have average hardness values of 19 and 10 GPa and elastic modulus of 234 and 157 GPa, respectively, which significantly exceeds the values of these parameters for the EBPBF-grown VT6 alloy. Electric discharge modification of the surface with multicomponent electrodes led to a decrease in roughness by 8...11 times due to the melting of the protrusions and filling of the dimples with the melt to a depth of more than 50 μm. A comparative analysis of the results of tribological tests showed a change in the wear mechanism as a result of EST of the additive VT6 alloy. Wear resistance increased by 4 and 3 orders of magnitude when using electrodes made of a bulk metallic glass and high-entropy alloy, respectively.

Исследование превращений переохлажденного аустенита при ступенчатой закалке стали 20Cr2Mn2SiNiMo

Currently, step quenching of steels in the temperature range of martensitic transformation, including quenching – partitioning, has found wide application in the automotive industry. Step quenching technology is successfully used to increase a set of properties, which most often include temporary tensile strength and relative elongation. The authors carried out a dilatometric study of the supercooled austenite transformations occurring in the 20Cr2Mn2SiNiMo steel, when implementing various options of step quenching with holding in the martensitic region. It was found that after single-stage quenching, single-stage quenching followed by tempering, and two-stage quenching, primary martensite, isothermal bainite, and secondary martensite are formed in various quantitative ratios. Using X-ray diffraction phase analysis, the amount of residual austenite was determined during step quenching. It has been shown that two-stage quenching makes it possible to stabilise up to 14 % of residual austenite, in the structure of the studied steel, at room temperature. Research has revealed that 20Cr2Mn2SiNiMo steel is characterised by a decrease in the crystal lattice parameter of the residual austenite, with an increase in its content in the steel structure. Uniaxial tensile and impact bending tests were carried out, and the values of the mechanical properties were determined. It has been found that during two-stage quenching, higher strength and elongation values, with lower values of relative contraction and impact strength are achieved compared to oil quenching and low-temperature tempering. The study showed that, with regard to the structural reliability of machine-building parts, step quenching is not the optimal heat treatment mode for the steel under study. The best combination of strength, ductility and impact hardness is achieved after quenching and low-temperature tempering.