When choosing compositions of high-entropy alloys, one of the parameters taken into account is thermal stability. The paper considers the structural transformations of the deformed Al0.3CoCrFeNi high-entropy alloy occurring during its annealing. The material was obtained by argon-arc melting with a mixture of pure single-element components. In order to homogenize the structure, the resulting ingot was subjected to thermomecha­nical processing according to a scheme combining cold rolling with a compression ratio of 50 % and low-temperature annealing (400 °C for 100 h). In the future, the homogenized billet was rolled in a cold state with a compression ratio of 80 %. The structure of the materials was studied directly during heating (in-situ mode) using the method of synchrotron X-ray diffraction. The heating rate of the samples was 20 °C/min, the maximum heating temperature was 1000 °C. The parameters of the alloy dislocation structure (density of screw dislocations, spatial distribution of dislocations) during heating were determined using the modified Williamson–Hall and Warren–Averbach methods. According to the data obtained, the temperature of beginning of formation of a high-entropy phase with a primitive cubic lattice is 560 °C. In the process of heating the material up to this temperature, an increase in density of screw dislocations and formation of a disordered dislocation structure are observed. The nature of change in dislocation density correlates well with the increase in the alloy microhardness. At an initial value of 406 ± 13 HV0.1 (for the deformed material), the microhardness during heat treatment increases up to 587 ± 10 HV0.1 .

The formation of wavy interface is one of the distinctive features of high-velocity impact welding. It is known that the geometric parameters of waves (amplitude a and length λ) depend not only on the impact conditions, but also on the mechanical properties of the materials being welded. However, until now, the impact of mechanical properties on the formation of waves has only been explored in a limited number of studies. To address this issue, in this paper, we use extensively a numerical simulation. First, we demonstrate that the numerical model, in conjunction with the smooth particle hydrodynamics (SPH) solver, effectively replicates the outcomes of a carefully controlled high-velocity impact welding experiment. Secondly, based on the validated model, we conducted a systematic study of the influence of strength on the wave formation process. Using numerical simulations with Johnson-Cook and ideal elastic-plastic strength models, we show that various characteristics of strength have a profound influence on the wave formation process. Furthermore, it is crucial to consider not only the yield strength of a material, but also factors such as strain and strain-rate hardening, along with thermal softening, to fully understand the wave formation during high-velocity impact welding.

The structure, microhardness, and tribological properties of coatings obtained in the process of surfacing of powder mixtures by an electron beam ejected into an air atmosphere are studied. For surfacing, we used a powder mixture containing amorphous boron and a wetting component, the role of which was played by Fe, Cr and Ni powder particles. The function of protecting the molten material from the air atmosphere was performed by MgF2 flux. The thickness of the formed coatings reached 2.3–2.8 mm. The maximum level of microhardness of coatings reaches 1500 HV. The main mechanism of hardening of such is due to the presence in the material of up to 90

The ultrafine-grained (UFG) structure and plastic deformation of the Ti-42Nb-7Zr alloy have been investigated using infrared thermography. The initial stage occurs at a constant temperature when the total energy of plastic strain absorbed by the alloy is 1.75 times higher for the UFG alloy, than for the alloy with a coarse-grained structure. This fact is due to substructural strengthening caused by severe plastic deformation and dispersion hardening with omega-phase nanoparticles. The amount of heat released before the UFG alloy fracture is 2 times larger than the amount of stored energy, and this results in localized softening of the UFG alloy prior to its fracture.

This paper presents a review of studies on pearlite, the most important structural constituent of carbon and low-alloy steels. It mainly focuses on the fine structure of pearlite revealed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Additionally, the paper highlights the key areas for future exploration to better understand the pearlite transformation in steels and the response of ferrite-cementite mixtures to different external loading conditions.

This study investigates the structure and properties of Al-Co-Cr-Fe-Ni high -entropy alloy (HEA) based coatings on steel substrates produced by non -vacuum electron beam cladding. Powder mixtures with Al molar ratios of 0.5, 1, and 1.5 were used for cladding, resulting in coatings with fcc, bcc + fcc, and bcc structures, respectively. The Fe content, which entered the coating from the substrate during cladding, increased from 9.9 up to 48.1 at. % with the decrease of the Al molar fraction from 1.5 to 0.5. In -situ synchrotron X-ray diffraction analysis showed that this effect can be attributed to the higher solidus temperatures of the compositions with higher Al content. Electron backscatter diffraction showed that differences in grain morphology and crystallographic texture were related to the crystallization temperatures in different zones of the coatings. The bcc coating with an Al molar ratio of 1.5 demonstrated superior hardness and wear resistance. Fcc coating, which received more Fe from the substrate, had lower hardness and was prone to plastic flow. However, the specific wear rate of the fcc coating was close to that of the bcc + fcc one due to the hardening of the fcc phase during sliding wear.

Results of investigation of the structure and properties of modified high-alloyed corrosion- and heat-resistant austenitic steel layers using the technology of non-vacuum electron-beam treatment are presented. Chromium and boron powders in various ratios have been used as modifying components. It has been established that Cr2B, (Fe,Cr)2B, and α- and γ-Fe phases are observed in the structure of the hardened layer, which directly affect the alloy properties. Tests carried out to assess heat and wear resistance showed that modification with chromium and boron makes it possible to increase the wear resistance by a factor of 4.3 and the heat resistance by a factor of 11.2 compared to the base metal.

Static tests of AFM carbon fiber samples made by autoclave and vacuum molding methods were carried out. Acoustic (acoustic emission and ultrasonic) methods, strain gauging, and microanalysis of thin sections were used to test for defects. The location of acoustic emission signals in the area of stress raisers made it possible to establish that the number of defects in autoclave molding is ten times less than under vacuum molding. Ultrasonic and acoustic emission methods, strain gauging, and microanalysis allowed determining the structure of AFM carbon fiber, the coordinates of defects, and their type. During the testing of unloaded samples made by vacuum molding, manufacturing defects were found that grew in size during static stretching and led to the occurrence of new destructions. No manufacturing defects were found in the samples produced by autoclave molding. Microanalysis of samples produced by the vacuum method revealed defects associated with fiber destruction, matrix cracking, and delamination. Tests of samples prepared by autoclave molding have shown that there are practically no defects in them.

Проанализированы особенности структурно-фазовых превращений, происходящих в процессе отжига сваренного взрывом биметалла Al – Zr. Показано, что термическая обработка приводит к формированию и росту на межслойной границе интерметаллидной прослойки, твердость которой достигает 9 ГПа. Методами микрорентгеноспектрального и рентгенофазового анализов с применением дифракции синхротронного излучения установлено, что возникший интерметаллидный слой состоит из фазы ZrAl3 со структурой типа D023. Периоды решетки данной фазы постепенно изменяются в направлении от границ металл – интерметаллид к центру слоя. С использованием квантово-химического моделирования методом функционала плотности показано, что на некотором расстоянии от границы ZrAl3 – Zr триалюминид циркония находится в наиболее стабильном состоянии, что обусловлено процессом собирательной рекристаллизации и сопутствующей аннигиляцией дефектов кристаллического строения.

Ti5Al11 is known as a high-temperature phase in binary Ti-Al alloys. However, its existence at low tem-peratures was previously observed in ternary Ti-Al-based systems alloyed with some transition metals. In this study, we systematically evaluated Ti-Al-Me ternary systems (Me = Au, Pd, Mn, or Pt) to determine the influence of transition elements on low-temperature stabilization of Ti5Al11 phase. The temperature ranges in which Ti5Al11 existed in Ti-Al-Me systems were experimentally found using in situ synchrotron X-ray diffraction (SXRD). It was established that addition of Mn and Pt retains Ti5Al11 at room temperature. The obtained data were compared with predictions of density functional theory (DFT). The total energy, volume, and bond length are especially significantly reduced by addition of Mn and Pt. Ti5Al11 compound containing both of these elements is less prone to saturation with Ti upon preserving the lattice tetragonality and suppressing Ti5Al11 -> TiAl transformation. These factors finally contribute to the retention of this phase at room temperature.(c) 2023 Elsevier B.V. All rights reserved.

We present the conceptual design of a universal materials-research beamline based on the undulator of a fourth-generation synchrotron-radiation source. The distinctive feature of the beamline is its capability to work with both spectrally narrow (Δ E / E ~ 10 –4 ) and relatively broad, high-intensity radiation beams (5 × 10 –2 ). The optical scheme enables rapid switching between diffraction, radiographic, and spectroscopic experimental methods while keeping the beam’s position fixed on the test sample and varying the spot size of the radiation from 100 nm to 1 mm.

Special features of structural transformations in steel 40Kh under friction observed in an operando experiment are studied using diffraction of synchrotron radiation. Variation of the chemical inhomogeneity of martensite under friction loading is determined and the effect of this phenomenon on defects of the crystal lattice of martensite is analyzed. It is shown that the interaction in the “alloy VK20 – steel 40Kh” pair under the specified conditions causes oxidation of the iron-carbon alloy and thus contributes into occurrence of steady friction wear.

Изучены особенности структурных превращений в стали 40Х в условиях трения, наблюдаемые в процессе operando эксперимента с использованием дифракции синхротронного излучения. Исследовано изменение химической неоднородности мартенсита при фрикционном нагружении и проведен анализ влияния этого явления на дефектность кристаллической решетки мартенсита. Показано, что взаимодействие пары “сплав ВК20 – сталь 40Х” в заданных условиях приводит к окислению железоуглеродистого сплава и, таким образом, способствует установлению режима устойчивого трения

Special features of structural and phase transformations occurring in annealing of an explosion-welded Al – Zr bimetal are considered. It is shown that heat treatment causes formation and growth of an intermetallic layer on the interface, which has a hardness of 9 GPa. The methods of microscopic x-ray spectrum analysis and of phase analysis with the use of synchrotron radiation are used to show that the intermetallic layer is represented by a ZrAl 3 phase with a D0 23 -type structure. The lattice constants of this phase vary gradually from the metal-intermetallic interfaces to the center of the layer. Quantum-chemical modeling by the method of density functional is used to show that the zirconium trialuminide is in the steadiest state at a certain distance from the interface due to the process of secondary recrystallization and the accompanying annihilation of crystal structure defects.

In this study, we discuss the structure and properties of high-entropy AlCoCrFeNi alloy after casting, cold deformation, and heat treatment. Ingots of the investigated alloys were obtained by arc melting method in argon atmosphere. In order to ensure a homogeneous chemical composition, ingots were remelted several times. Cylindrical samples of 5 mm in diameter and 8 mm in height were cut from ingots by electrospark method for mechanical tests. Subsequently, samples were subjected to uniaxial compression by 5, 11, and 23 %. During the tests, compression curves were recorded, and limit of proportionality of the analyzed alloys was calculated. High-temperature annealing and thermal studies were performed using thermogravimetric analyzer. Thermal studies were carried out in a cyclic mode (3 cycles, including heating up to 1200 °C at a rate of 20 °C/min and cooling at a rate of 20 °C/min). High-temperature annealing was carried out at a temperature of 1200 °C for 5 hours. Such annealing of cast alloys promotes material homogenization and eliminates dendritic structure. The alloy presents limited plasticity. Grain boundaries are effective barriers preventing crack propagation. The studies indicate that plastic deformation has a significant effect on development of relaxation processes during subsequent heat treatment. An increase in strain during the compression leads to a higher rate of healing processes of defects in crystal structure.

The paper considers the features of structural transformations during annealing of the high-entropy alloy Al0.3CoCrFeNi. The ingots obtained by argon arc melting were subjected to cold rolling with a compression ratio of 50 %. The produced worpieces were annealed in the furnace for 4 hours at temperatures of 200, 400, 600, 800 and 1000 °C. The samples obtained by the described technique were examined using the methods of synchrotron X-ray diffraction in the lumen mode and diffraction of backscattered electrons. The research data indicate that up to a temperature of 600 °C, the structure of the alloys is represented by a single phase with a face-centered cubic lattice. When annealing alloys at temperatures of 800 and 1000 °C, the phase composition is characterized by the presence of two phases: a disordered phase with a face-centered cubic lattice and an ordered phase with a primitive cubic lattice. At temperatures above 800 °C, the burning of alloys is accompanied by development of recrystallization processes. It was found that after annealing at 800 °C, the relative proportion of micro-volumes characterized by inter-angular misorientation of more than 10° was 20 %, and after annealing at 1000 °C – 65 %. Microhardness of the studied samples increases with an increase in temperature up to 600 °C and decreases with a further increase in temperature. Analysis of the width of diffraction maxima using the methods of profile analysis of diffractograms indicates an increase in distortions of the crystal lattice of the ordered phase. This behavior may be associated with the release of nanoscale inclusions in the matrix of the main phase.

Introduction. The interest of modern medical materials science is focused on the development of beta-alloys of ternary systems (TNZ) based on titanium, niobium and zirconium with the low Young’s modulus, which is comparable with the elastic modulus of the bone. A wide application of the above alloys in medicine is limited by its insufficiently high strength properties, such as yield strength, ultimate strength, fatigue strength, fatigue life, etc. The formation of bulk ultrafine-grained structure in the alloys via deformation processing, including severe plastic deformation, ensures a considerable increase in the mechanical properties of alloys without toxic alloying elements. The aim of the work is to analyze the influence of deformation (multipass rolling and abc-pressing in combination with rolling) on the microstructure and mechanical properties of the alloy of the Ti-Nb-Zr system. The research methods. The Ti-42Nb-7Zr alloy cast blanks were made from pure titanium, niobium, and zirconium iodides by arc melting with a tungsten electrode in the protective argon atmosphere. It is shown that the cast blanks obtained have a high degree of uniformity in the distribution of niobium and zirconium alloying elements. To form an ultrafine-grained (UFG) structure, the cast blanks were subjected to deformation according to two schemes: 1) multipass rolling and 2) a combined method of severe plastic deformation, consisting in abc-pressing and subsequent multipass groove rolling. Results and discussion. As a result of deformation processing by rolling, an ultrafine-grained (UFG) structure is formed, which is represented by non-equiaxed -subgrains with cross-sectional dimensions 0.2…0.8 µm and length 0.2…0.7 µm, dispersion strengthened nanosized ω-phase, as well as subgrains of the -phase. Application of combined severe plastic deformation has promoted formation of a more dispersed UFG (+ω)-structure with an average size of structural elements equal to 0.3 μm. The UFG structure formed as a result of two-stage SPD has provided a high level of mechanical properties: yield strength – 480 MPa, ultimate strength – 1.100 MPa, microhardness – 2.800 MPa, with a low modulus of elasticity equal to 36 GPa.

This paper is devoted to characterization of microstructure and phase constituion of coatings produced by non -vacuum electron beam cladding of Ni-Cr-Si-B self-fluxing alloy with Nb and amorphous B additions on mild steel substrates. The main purpose of this study was to form niobium diborides (NbB2) belonging to AlB2 structural family directly during the cladding process. For this reason we carried out a series of experiments with different ratios of (Nb+B(Am)) and Ni-Cr-Si-B powders. When the starting material contained 15-40 wt% of (Nb+B(Am)) powder the NbC and (Cr, Fe)23C6 carbides, as well as NbB2 particles distributed in gamma-(Ni-Fe) solid solution, were formed. When the starting powders contained 30-40 wt% of (Nb+B(Am)), NbB2 formed shells around the NbC particles. The mechamism of shells formation, the ordering of gamma-(Ni-Fe)-matrix and other structural peculiarities of the samples are discussed in the paper. Microhardness of the samples materials ranged from 450 to 950 HV0.1.

The possibility of forming coatings with a high content of amorphous phase by knock (detonation) spraying of a powder of alloy Fe66Cr10Nb5B19 of fraction 45 – 75 μm is considered. Results of comparative tests of the coatings and of a stainless steel check test piece for abrasive wear under friction against nonrigidly fixed abrasive particles conducted according to ASTM G65D are presented. The wear mechanisms of the knock-sprayed coatings with partially crystallized structure are studied.

The method of smooth particle hydrodynamics and the ANSYS AUTODYN software are used to reproduce the main phenomena accompanying high-velocity collision of plates fabricated from iron and copper of commercial purity. The maximum true strain of the surface layers is determined to attain ε = 5 or higher values. It is shown experimentally that defects with a length comparable to the thickness of the original plates do not form under welding by optimum modes. Growth in the strength properties is a factor promoting formation of bands of localized flow under rapid loading. Defects of this kind correspond to the behavior of positive feedback loops. The width of the bands arising under explosion welding of plates from a two-phase (α + β) titanium alloy VT23 ranges from units to tens of micrometers.