Konovalov, Sergey V

Pecherskaya E.A., Semenov A.D., Zinchenko T.O., Gurin S.A., Konovalov S.V., Novichkov M.D., Shepeleva A.E., Tuzova D.E.

Peng F.C., Guo C., Jiang F., Yuan D., Yin H., Sun Q., Zhang H., Dong T., Guo D., Konovalov S.

Gromov V.E., Konovalov S.V., Polevoi E.V.

JSC EVRAZ United West Siberian Metallurgical Plant is the main manufacturer of rails in the Russian Federation. The work traces the evolution of the plant’s rail assortment over the past quarter century. A brief review of publications on modern concepts of the formation of structural and phase states of defective substructure and properties of volumetrically and differentially hardened pre-eutectoid, trans-eutectoid and bainite rails during production and subsequent long-term operation was performed. The service life of rails is determined by many factors: metal purity, structure, phase composition, operating conditions, heat treatment technology, etc. Special attention is paid to a new type of rail products – rails of the DT400IK category with increased wear resistance and contact endurance made of eutectoid steel, designed for use in difficult conditions. The paper considers the promising areas of rail assortment expansion.

Song H., Guo C., Wu Y., Jiang F., Chen L., Xiao M., Jiao B., Dong T., Wang S., Qiao Z., Konovalov S.

In order to investigate the influence of ultrasonic vibration (UV) on microstructural evaluation of amorphous coating, the Fe-based amorphous (Fe

Chen Z., Su Y., Li H., Wang X., Liu L., Yang Z., Tang H., Lv W., Chen J., Li N., Konovalov S.

Пимонов М.А., Коновалов С.В., Дриц А.М., Зорин И.А., Арышенский Е.В.

Исследование посвящено изучению влияния гафния на антирекристаллизационные свойства сплава 1570. В процессе исследования сплав 1570 и его модификации, содержащие 0,2 % и 0,5 % масс. гафния, исследовались в литом и гомогенизированном состояниях при помощи просвечивающей электронной микроскопии. В результате выявлено, что легирование гафнием 0,2 % масс. при отжиге в течение 4 часов при температуре 370 °С приводит к снижению объема выделившихся частиц по сравнению со сплавом 1570. При повышении концентрации гафния до 0,5 % количество частиц продолжает уменьшаться. Теоретические расчеты тормозящей и движущей сил рекристаллизации показывают, что в сплавах, содержащих гафний 0,5 % масс., при высоких параметрах Холомона-Зенера возможно протекание рекристаллизации. Отжиг при температуре 440 °С приводят к увеличению доли и уменьшению размера частиц в сплавах с содержанием гафния. Особенно сильно уменьшается размер частиц и растет их объем в сплаве с содержанием гафния 0,2 %. Таким образом, в сплавах, легированных гафнием, рекристаллизация блокируется при любых рассмотренных в данной работе параметрах Холломона-Зенера. В сплаве без гафния рост температуры отжига, наоборот, приводит к уменьшению количества частиц и увлечению их размера. В результате тормозящая сила несколько снижается, однако ее все равно достаточно для полного торможения процессов рекристаллизации.

Ефимов М.О., Юрьев А.Б., Коновалов С.В., Громов В.Е.

Пятикомпонентные высокоэнтропийные сплавы ВЭС типа сплава CoCrFeNiMn Кантора, обладающие хорошим сочетанием прочностных и пластических свойств и имеющие благоприятные перспективы практического использования, вот уже более четверти века активно исследуются во всем мире. В статье представлен краткий обзор публикаций в основном зарубежных исследователей по поиску направлений изменения, (улучшения) свойств этих сплавов и их практическому применению. Проанализированы теоретические и экспериментальные работы, свидетельствующие о возможности электронных структур в формировании свойств высокоэнтропийных сплавов. Изучение магнитных свойств ВЭС, может дать важную дополнительную информацию об их электронной структуре. На примере ВЭС (CoCrFeMn)1-хNiх, содержащих пять ферромагнитных элементов, прослежена эволюция магнитной природы с изменением температуры. Обращено внимание на необходимость ускорения масштабного практического применения ВЭС. Показаны трудности и сдерживающие факторы практического использования ВЭС и пути их преодоления. В этом направлении проведен анализ публикаций в зарубежной печати о путях создания ВЭС из отходов (лома) машиностроительной и металлургической промышленности. Выполнено сравнение структурно-фазовых состояний и механических свойств ВЭС, изготовленных из чистых составляющих элементов и отходов, содержащих нержавеющую сталь, нихром, кобальтовые сплавы.

Shubert A., Konovalov S., Panchenko I.

Introduction. The paper discusses the prospects for studying high-entropy alloys (HEA), metal materials with unique properties. The study of high-entropy alloys is an urgent area of research in connection with its properties, environmental sustainability, economic benefits and technological potential. HEA are of interest to researchers due to its stability, strength, corrosion resistance and other characteristics, which makes it promising for use in the aerospace industry, automotive, medicine and microelectronics. Thus, HEA research contributes to the development of new materials and technological progress, providing opportunities for creating innovative products and improving existing solutions. To effectively use the potential of high-entropy alloys, research is required in a number of areas. First, it is necessary to improve the production technology of such alloys and develop new methods for obtaining HEA with improved characteristics and reduced cost. Secondly, it is necessary to establish the basic principles of operation of high-entropy alloys and to study the mechanisms influencing its properties. It is also necessary to develop new alloys with specified properties and conduct experiments and computer simulations to optimize the characteristics of the alloys and determine the best compositions. The purpose of the work is to study developments in the field of high-entropy alloys and conduct a comparative analysis of published studies on improving the properties of high-entropy alloys. The research method is a review and analysis based on developments mainly for 2020-2024, which were carried out by domestic and foreign scientists. The paper discusses the prospects for the study of high-entropy alloys, materials with a wide range of applications in various industries. The paper presents the results of research, mainly for 2020-2024. The main properties of high-entropy alloys are described, such as high strength, corrosion resistance, fatigue properties, plasticity and deformability, thermal stability, electrical conductivity and magnetic properties, as well as the possibility of creating alloys with specified characteristics. The most common methods of changing the properties of alloys have been identified. The directions of further development of research in this area are considered. Results and discussion: a literature review shows that developments and research are carried out on all possible properties of HEA, but most of it is devoted to corrosion-resisting properties and thermal stability. Of the methods used in high-entropy alloys, the most common and universal can be considered the alloying of high-entropy alloys with other metals. Studies also confirm that alloying metals are selected depending on its characteristic properties. The number of scientific works also confirms the relevance of this topic and the need for its study. The authors noted that future studies on the fatigue properties of high-entropy alloys, as well as the properties of alloys under the influence of magnetic and electric fields are the most interesting.

Pecherskaya E.A., Konovalov S.V., Golubkov P.E., Mitrokhin M.A., Gurin S.A., Novichkov M.D.

Micro-arc oxide coatings of aluminum alloy AD31 samples were formed in an electrolyte containing 2 g/l NaOH and 9 g/l Na2SiO3 for 2, 4, 8, 16 min in the anode and anode-cathode modes. During the processing, the forming curve, the time dependences of the charge passed through the galvanic cell, and the optical parameters of the microdischarges were measured using the optical synchronization method developed by the authors with subsequent image recognition. The thickness of the coatings was measured using a point autofocus probe surface texture measuring instrument Mitaka PF-60, the surface morphology was studied using a VEGA3 scanning electron microscope using SBH surface topography. The elemental composition of the coatings was determined using a scanning electron microscope JSM-6610LV. The analysis of the elemental composition and morphology of the surface revealed that the inner layer of synthesized coatings consists of Al2O3, the outer layer consists of Al2O3·SiO2 mullite, and the ratio of phases Al2O3 and mullite changes with changes in current density and oxidation mode. The formation of mullite is due to the presence of Na2SiO3 in the electrolyte. It is shown that with increasing processing time and current density, the thickness, roughness and porosity of coatings increase. The interrelation of the optical parameters of microdischarges with the morphology of the surface and the elemental composition of the formed coatings is substantiated; it is shown that the ratio of illuminated and non-illuminated sections of the sample surface by microdischarges can be used as a rough estimate of the ratio of electron and ion currents corresponding to microplasma and electrochemical processes. A mathematical model describing the dependence of the coating thickness on the oxidation time based on Faraday's laws for electrolysis and the results of measuring the optical parameters of microdischarges and the electrical parameters of the MAO process without taking into account microplasma processes that do not lead to an increase in the thickness of coatings is proposed. The error of adequacy of the proposed model does not exceed ±10 %. The results of the study can be used in the development of a digital twin of the micro-arc oxidation process.

Konovalov S., Gudala S., Panchenko I., Osintsev K., Chen X.

In the present study, the microstructure and mechanical properties of various CoCrFeMnNi high-entropy alloys were investigated. Analytical studies were conducted to determine the optimal chemical composition, mixing entropy, mixing enthalpy, atomic radii, valence electron concentration (VEC), dimensionless parameter, and melting point on the Co-Cr-Fe-Mn-Ni system. The microstructure of the alloys was analyzed using FESEM, XRD, and TEM. The results showed that the microstructure of all HEAs had dendritic and interdendritic regions, with secondary precipitations detected along the grain boundaries of the alloy, mainly composed of Mn and Ni. High-density dislocation structures and nano-precipitates were predominantly present in the alloy. The mechanical characteristics such as microhardness and tensile properties are conducted at room temperature. The HEA Co25Cr25Fe10Mn30Ni10 exhibited the highest average microhardness, while the Co20Cr20Fe30Mn10Ni20 HEA had the lowest mean hardness value. This significant difference of 7.2 % may be attributed to the hard phases composed of Mn and Ni. The results of the tensile experiments indicate that the Co20Cr20Fe20Mn20Ni20 alloy has the most favorable overall properties, with an ultimate tensile strength of 441 MPa. This represents a significant increase of 37.8 % compared to 20Cr20Fe20Mn20Ni20. Furthermore, the study examines the instability of the solid-solution state caused by differences in the valence electron concentrations of the constituent elements and phase stability.

Efimov M.O., Gromov V.E., Konovalov S.V., Panchenko I.A., Semin A.P.

Gromov V.E., Konovalov S.V., Efimov M.O., Panchenko I.A., Shlyarov V.V.

Created one of the first and studied more than 20 years ago, high-entropy five-component alloys CoCrFeNiMn (Cantor alloy) and CoCrFeNiAl still attract the attention of researchers in the field of physical materials science due to their possible application in various industries because of their successful combination of strength and plastic properties. To date, a large amount of experimental materials has been accumulated on the ways to control the properties of these alloys. This article reviews the publications of domestic and foreign authors in two areas of improving the properties of these alloys: alloying, precipitation and heat treatment, and the use of CALPHAD phase diagrams. In the first direction, the role of alloying with B, Al, V, Si, Nb is analyzed; γ and γ′ nanoprecipitations, various modes of thermal and deformation processing. It was concluded that it is necessary to conduct experiments on the alloying of HEAs with Zr and Nb, which have proven themselves well in hardening steels. Creation and modification of the properties of five-component HEAs is possible using the CALPHAD computer programs developed for calculating state diagrams. The results of publications on the thermodynamic description of five-component alloys analyzed in the article are confirmed by comparing the phase diagrams with the available experimental data. In one of the analyzed works on the phase formation of five-component HEAs consisting of Co, Cr, Fe, Ni, Al, Mn, Cu, 2436 compositions were considered, which made it possible to determine 1761 variants of reliab­le prediction of the formation of bcc/B2 and fcc phases, bypassing amorphous phases and intermetallic compounds, thereby designing a certain level of mechanical properties. It is shown that the design of a new generation of HEAs is possible based on calculation of the CALPHAD phase diagrams.

Panchenko I.A., Konovalov S.V., Drobyshev V.K., Labinsky D.N., Khusainov Y.G., Nazarov A.Y.

Zorin I.A., Drits A.M., Aryshensky E.V., Konovalov S.V.

Aryshenskii E.V., Aryshenskii V.Y., Ragazin A.A., Rasposienko D.Y., Grechnikov F.V., Makarov V.V., Konovalov S.V.

The study addresses the effect of 1580 and 1590 alloys cold rolled strip annealing practices on the alloys’ grain structure and mechanical properties. The 1590 alloy differs from the 1580 alloy by hafnium and erbium additions. Samples of such alloys were produced by casting into a steel mold. After that they were homogenized during 4 h at 440°С. Then the samples were hot rolled at 440°С, with further cold rolling to 2 mm, with the cumulative percentage reduction equal to 66%. The cold rolled strip was annealed at the temperature ranging from 330 to 440°С with 1 h soaking. The sizes and morphology of Al3Sc strengthening nanoparticles were examined in homogenized condition using transmission microscopy. The mechanical properties and grain structure were defined in cold rolled and annealed conditions. During homogenizing annealing in the 1590 alloy finer strengthening nanoparticles are formed compared to the 1580 alloy. Such features of the microstructure can be explained by the presence of erbium, promoting formation of additional Al3Sc-type nanoparticles nuclei, and hafnium, preventing their further growth. Non-recrystallized structure was identified in both alloys after cold rolling and final annealing. The 1590 alloy has better mechanical properties, regardless of the annealing temperature, which is explained by a larger portion and smaller size of strengthening nanoparticles.

Du C., Xie H., Liu J., Lei B., Zhang R.

Song C., Wang G., Zhao X., Han Q., Yin F.

Shen C., Ma Y., Pan Z., Li F., Zhang Y., Wang L., Li Y., Li H., Hua X.

Chen R., Lu W., Sun F., Sun L., Wu P., Zou J., Fang N., Huang L., Wang C., Jin J., Zhang X., Geng L.

Li X., Yang Y., Shen H., Zhou M., Huang B., Cui L., Hao S.

Song B., Han Y., Gao L., Sun H., Cheng J., Jin X., Hong H., Huang J.

Zhang Z., Tu J., Zhang X., Qiu Y., Du Y., Liang Y.

Trink B., Weißensteiner I., Uggowitzer P.J., Samberger S., Coradini D.S., Falkinger G., Strobel K., Pogatscher S.

Du Z., Li X., Zheng M., Rogozhkin S.V., Nikitin A.A., Pan H.

Kurzawa A., Stachowicz M., Roszak M., Roik T., Gavrysh O., Maistrenko I., Jamroziak K., Bocian M., Lesiuk G.

Luo W., Liu Y.

Tyagi R., Sunil B.D., Kumar M., Bishwakarma H., Saxena K.K., Chandrashekar R., Ali J., Sehgal L., Lakshmi A.A.

Gong P., Kwok T.W., Wang Y., Dawson H., Goodall R., Dye D., Rainforth W.M.

Abstract Fusion reactor materials for the first wall and blanket must have high strength, be radiation tolerant and be reduced activation (low post-use radioactivity), which has resulted in reduced activation ferritic/martensitic (RAFM) steels. The current steels suffer irradiation-induced hardening and embrittlement and are not adequate for planned commercial fusion reactors. Producing high strength, ductility and toughness is difficult, because inhibiting deformation to produce strength also reduces the amount of work hardening available, and thereby ductility. Here we solve this dichotomy to introduce a high strength and high ductility RAFM steel, produced by a modified thermomechanical process route. A unique multiscale microstructure is developed, comprising nanoscale and microscale ferrite, tempered martensite containing fine subgrains and a high density of nanoscale precipitates. High strength is attributed to the fine grain and subgrain and a higher proportion of metal carbides, while the high ductility results from a high mobile dislocation density in the ferrite, subgrain formation in the tempered martensite, and the bimodal microstructure, which improves ductility without impairing strength.

Speirs D.C., Ruiz Ruiz J., Giacomin M., Hall-Chen V.H., Phelps A.D., Vann R.G., Huggard P., Wang H., Field A.R., Ronald K.

Abstract Plasma turbulence on disparate spatial and temporal scales plays a key role in defining the level of confinement achievable in tokamaks, with the development of reduced numerical models for cross-scale turbulence effects informed by experimental measurements an essential step. MAST-U is a well-equipped facility having instruments to measure ion and electron scale turbulence at the plasma edge. However, measurement of core electron scale turbulence is challenging, especially in H mode. Using a novel synthetic diagnostic approach, we present simulated measurement specifications of a proposed highly optimised mm-wave based collective scattering instrument for measuring both normal and bi-normal electron scale turbulence in the core and edge of MAST-U. A powerful modelling framework has been developed that combines beam-tracing techniques with gyrokinetic simulations to predict the sensitivity and spectral range of measurement, with a quasi-numerical approach used to analyse the corresponding instrument selectivity functions. For the reconstructed MAST 022769 shot, a maximum measurable normalised bi-normal wavenumber of k ⊥   ρ e ∼ 0.6 was predicted in the core and k ⊥   ρ e ∼ 0.79 near the pedestal, with localisation lengths L FWHM ranging from ∼0.4 m in the core at k ⊥   ρ e ∼ 0.1 to ∼0.08 m at k ⊥   ρ e > 0.45. Synthetic diagnostic analysis for the 022769 shot using CGYRO gyrokinetic simulation spectra reveal that electron temperature gradient turbulence wavenumbers of peak spectral intensity comfortably fall within the measurable/detectable range of the instrument from the core to the pedestal. The proposed diagnostic opens up opportunities to study new regimes of turbulence and confinement, particularly in association with upcoming non-inductive, microwave based current drive experiments on MAST-U and can provide insight into cross-scale turbulence effects, while having suitability to operate during burning plasma scenarios on future reactors such as Spherical Tokamak for Energy Production.

Ding A., Tang F., Alsberg E.

Zhang P., Deng Q., Fu Z., Shen Z., Li X., Sun D., Cai Z., Gu L.

In the aerospace industry, fretting and sliding wear are commonly encountered by components made from M50 bearing steel. This study aims to investigate the effect of temperature on the fretting and sliding wear behavior of M50 bearing steel. Research indicates that as the temperature rises from 25 ℃ to 350 ℃, the average friction coefficient decreases in fretting conditions and initially increases before decreasing in sliding conditions. At 350 °C, increased oxidation occurred, resulting in the formation of oxides mainly composed of Fe2O3 and Fe3O4, with small amount of MoO3 and Cr2O3. The elevated temperature causes more oxide adhering to the surface and forming a protective oxide film, thus reducing the friction and wear.

Pei W., Pei X., Xie Z., Wang J.

The marine environment has caused significant economic losses to marine engineering machinery, and the exploitation of simple, environmentally friendly, economical, mechanically durable marine protective coatings is imminent. This article provides a comprehensive review of the recent research advancements in marine metal protective coatings, such as superhydrophobic coatings, micro-arc oxidation coatings, laser cladding coatings, and graphene nano-anticorrosion coatings. The review explores their respective anticorrosion strategies, anticorrosion and wear-resistant mechanisms, preparation processes, and influencing factors. Ultimately, it summarizes the challenges in the practical application of marine coatings in marine corrosion protection, which provides an outlook on the future direction of coating development. The application of marine anticorrosion and wear-resistant coatings provides reliable protection to ensure the regular operation of marine resource development facilities.

Li T., Hu M., Pei X., Du Y., Zhou W., Wang H.

A novel Al0.8TiVNbNi0.2(SiC)0.2 RHEA-based composite was fabricated by spark plasma sintering. The microstructure evolution and distinctions in high-temperature tribological properties of composite incorporating SiC nano-particles were systematically analyzed. The results demonstrate that SiC particles undergo in-situ reactions with the matrix alloy during the sintering process, resulting in the formation of TiC and Nb5Si3 phases, which significantly increases the microhardness of the composite. Simultaneously, wear resistance of Al0.8TiVNbNi0.2(SiC)0.2 composite is sharply ameliorated in a wide temperature range (RT to 800 °C). The non-exogenous matching interface between reinforced phases and matrix is the key to good tribological performance. For another, the generated Si oxides is contribute to continuity of the tribo-layer formed at high-temperatures, leading to a conspicuous reduction of wear rates.

Kausar A., Eisa M.H., Aldaghri O., Ibnaouf K.H., Mimouni A.

Exceptional category of alloys comprising five or more alloying metals in structures are referred as high entropy alloys. Uniqueness of these alloys have been observed due to the combination of superior mechanical, thermal, conducting, anticorrosion, and other physical properties. Unlike traditional metallic alloys (two metals), the varying elemental compositions led to limitless potential possibilities. Recent research has unveiled an important opportunity for high entropy alloys based nanostructures like nanoparticles and nanocomposites. This state-of-the-art review is basically intended to highlight the design and essential structure, property, and applied aspects of essential high entropy alloy based nanostructures. Consequently, various notable nanoparticles and combinations of high entropy alloys with carbon nanoparticles (graphene, carbon nanotube) and inorganic nanoparticles have been surveyed. In this context, several nanocomposite designs have been reported using the efficient techniques like thermal shock, flame spray pyrolysis, plasma spark sintering, mechanical milling, alloying, electrochemical, and solution to name a few. The resulting high entropy alloy derived nanomaterials have been researched for microstructure, nanocrystalline structure, different mechanical features (microhardness, modulus, stress–strain, compression properties), wear, electrochemical, thermal, and range of other physical properties. Consequently, research on high entropy alloy nanostructures has pointed towards the applied fields of energy storage (batteries and supercapacitors), radiation shielding, corrosion/wear coatings, and biomedical uses.

Fan K., Liu D., Zhou K., Liu Y., Zhang H., Zhang X., Li Y., Li M., Li Y., Abdel Wahab M.

In this paper, ultrasonic surface rolling (USRP) and laser heating-assisted USRP (Laser-USRP) techniques are employed to enhance the fretting fatigue strength of TC11 titanium alloy. Furthermore, the surface deformation mechanism and fretting fatigue behavior are investigated. The properties of the reinforced surfaces were observed using transmission electron microscope (TEM), microhardness test, residual stress test and fretting fatigue experiments. The results showed that laser-USRP led to a remarkable enhancement in the fretting fatigue life of TC11 titanium alloy compared to traditional USRP. This was mainly due to the fact that laser heating improved the plasticity of TC11 titanium alloy, contributed to the formation of a smoother surface and increased the degree of surface oxidation, which could improve surface lubrication. Under high temperature, more slip systems were activated and more stable dislocations were formed, which resulted in larger compressive residual stress (CRS) with higher stability. The superposition of the elevated temperature field and the kinetic energy of the ultrasonic vibration produced an annealing effect in localized regions, resulting in the formation of more stable gradient nanograins. This study demonstrated the immense potential of laser-assisted plastic deformation in improving the surface properties of titanium alloys.

Shao B., Liu J., Su H., Zong Y., Shan D., Guo B.

7075 aluminum alloy is widely used in the aerospace field because of its low density, high specific strength, high fracture toughness, and good machinability. This paper systematically studied the evolution of the microstructure and properties of 7075 aluminum alloy at different temperatures. Based on the rolling and heat treatment process, a short process of rolling and heat treatment is proposed, which can significantly improve the properties. The study found that the nano‐phases were distributed in a “streamline‐like” or “lip‐like” shape after rolling. When the rolling temperature was below 550°C, the phases were mainly Al7Cu2Fe, the grain size did not change significantly, and shear bands appeared inside the grains. When rolled at 600°C, the grains coarsened significantly and the shear bands became longer, resulting in overburning and cracking. The broken phases were smoothed when rolled at 550°C. It was observed that the nano‐phases became larger. Due to the strain‐strengthening effect, the UTS increase by 6% with little change in elongation. In industrial production, direct aging treatment after high‐temperature rolling can reduce energy consumption and improve production efficiency.This article is protected by copyright. All rights reserved.

Richter B., Hocker S.J., Frankforter E.L., Tayon W.A., Glaessgen E.H.

Cavitation and acoustic streaming created by in situ high-intensity ultrasound have been exploited for microstructural refinement during directed energy deposition (DED) additive manufacturing (AM) of alloy Ti-6Al-4V. Whether the same ultrasound-driven mechanisms are applicable to powder bed fusion (PBF) of Ti-6Al-4V remains uncertain. The primary factors that control the microstructure during deposition processing are the solidification velocity and temperature gradient, which are orders of magnitude higher for PBF than DED processes. This work examines the role of high-intensity ultrasound on the melt pool and resulting microstructure of Ti-6Al-4V under PBF solidification conditions. The effect of the laser scanning velocity and ultrasonic excitation on the melt pool and grain structure characteristics is interrogated through controlled line scans and area scans without powder. Temperature field simulations are used to estimate the solidification velocities and temperature gradients and to compare the processing conditions with previously characterized columnar-to-equiaxed transition diagrams. The acoustic pressures during processing are estimated using a coupled field acoustic-elastic finite element simulation and used in a Keller-Miksis model to assess the likelihood of cavitation vs. cavity size. The microstructure of the samples with or without ultrasonic excitation was characterized, allowing the equivalent grain diameters and aspect ratios to be compared. All samples, including those exposed to scanning velocities where cavitation did not occur, showed a reduction in grain aspect ratio when subjected to ultrasonic excitation, but the effect on equivalent grain diameter was inconclusive. A key finding is that the primary effects of ultrasonic excitation may be attributed to acoustic streaming, rather than cavitation, during PBF processing. Further development of the ultrasonic excitation technique explored may permit tailoring of the microstructure and texture characteristics in bulk AM parts.

Zhong B., Dang J., Xue S., Wang D., Liu Z., An Q., Chen M.

Turning process will bring about surface modification in microstructure of strengthening layer, further leading to changes in mechanical properties. This article took cutting experiments and characterization techniques to study and analyze the surface modification of strengthening layer during the turning process, including grain size, grain misorientation angle, and kernel average misorientation. Scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscope (TEM) were used to characterize experimental samples based on the Taguchi method to study influences of cutting parameters and heat treatment states on the surface modification of strengthening layer. Additionally, a nanomechanical testing system was used to obtain microhardness of the surface. Finally, the above analysis was verified by cutting chips. It shows that a larger cutting relative evaluation coefficient is conducive to obtaining a thicker strengthening layer and finer grains, thereby obtaining excellent machined surface properties.

Titarmare V., Banerjee S., Sahoo P.

Abrasive wear behavior of AZ31 −B4C composites having varying amount of B4C particles (0 −2 wt%) is investigated. AZ31 −B4C composites are synthesized through ultrasonic assisted stir casting method. Characterizations of as-cast composites are performed through optical microscopy and field emission scanning electron microscopy. Compositional analyses are performed using energy dispersive X-ray analysis (EDS). Microstructural analyses disclose uniform distribution of B4C ceramic particles in AZ31 matrix. Compositional analyses confirm incorporation of B4C particles in AZ31 matrix. Both microhardness testing and density measurements are performed. Microhardness value is enhanced by 54.9% compared to base alloy by incorporating 2 wt% of B4C particles. Pin-on-disk tribotester is employed to scrutinize abrasive wear and friction characteristics of developed materials at varying sliding distance (40, 50 and 60 mm track dia.) and different abrasive grits (400, 500 and 600 grit). Wear rate of AZ31 alloy is about 1.3 − 1.5 times more than AZ31 − 2.0B4C composite for all experimental conditions. Wear rate reduces with increase in abrasive grit size while the same increases with increase in sliding distance. Finally, worn surface morphology of developed materials is also analyzed through FESEM and EDAX spectra. Examination of worn surface morphology discloses that abrasion and oxidation are dominant for composite samples.

Fan N., Chen T., Ju J., Rafferty A., Lupoi R., Kong N., Xie Y., Yin S.

To improve the wear resistance of CoCrFeNi HEA alloy for a wider range of industrial applications, the alloying strategy was applied to CoCrFeNi HEA by doping Mo element in various ratios, and CoCrFeNiMox (x=0, 0.2, 0.5, and 1) deposits were fabricated by cold spray. The microstructure evolution, mechanical properties, and tribological properties of cold-sprayed CoCrFeNiMox deposits were systematically investigated. The results showed that Mo0, Mo0.2, and Mo0.5 deposits have a face-centered-cubic (FCC) single structure, while Mo1.0 deposit was composed of FCC matrix and hard brittle phases. The doping of Mo element into CoCrFeNi HEA deposits significantly increased the hardness due to the enhanced solid solution strengthening and precipitation strengthening. As a result, the anti-wear properties of Mo-doped CoCrFeNi HEA deposits were gradually improved with the increase in Mo ratios. To be specific, the Mo1.0 deposit exhibited the lowest specific wear rate of 0.51 × 10-4 mm3/ N·m, which was reduced by 94.9% in comparison to the Mo0 deposit. Overall, the current study proposes a new strategy to manipulate the mechanical properties of cold-sprayed high-entropy alloy deposits by alloying.

Guo C., Xu S., Chen Z., Gao H., Jiang G., Sun W., Wang X., Jiang F.

The B4C/Inconel 625 composite coatings were successfully prepared on 20 pipeline steel by laser cladding, in which B4C ceramic was selected as reinforcement phase to improve the microstructure and corrosion property of Inconel 625 coating. The laser cladding parameters were optimized and the effect of B4C content and B4C particle sizes on the microstructure and properties of B4C/Inconel 625 composite coatings were studied in detail. With increasing liner energy density and decreasing powder feeding speed, the crack ratio of the composite coatings reduces. NiB phase forms due to the in-situ reaction of B4C with Ni element in Inconel 625, and a thin layer of planar crystal also forms at the coating/substrate interface. As the addition of B4C content ranged 5wt.%∼10wt.% and the particle sizes ranged 10μm∼60μm, the quantities of equiaxed crystals increase obviously and the coarse columnar crystals are also refined, which contributes to the improved microhardness and corrosion resistance of the B4C/Inconel 625 composite coatings. When the B4C content is 10wt.% and particle size is 10μm, the maximum microhardness of the composite coating is about 567HV0.2, which is 241.2% to that of Inconel 625 coating. The optimal corrosion resistance of B4C/Inconel 625 composite coatings is obtained when the B4C content is 5wt.% and particle size is 60μm.

Yuan Y., Li R., Bi X., Yan M., Cheng J., Gu J.

Ultrasonic Impact Treatment (UIT) is a surface treatment method that uses ultrasound to create high-frequency, high-intensity impact loads on the surface of metallic materials to improve material properties and durability. The current state of research on the numerical simulation of UIT is reviewed in this paper. Firstly, the working principle of UIT strengthening is introduced, which includes the application of high-intensity UIT to the surface of metallic materials. The UIT strengthening technology has achieved significant success in the industrial field, resulting in plastic deformation, surface compression and residual stress, thereby significantly improving material properties. Secondly, the influence of UIT on the microstructure is reviewed. It is found that the grain refinement and dislocation are successfully predicted by finite element simulation and other methods. The influence of UIT on residual stress is reviewed. It is found that UIT can effectively transform harmful tensile stress into compressive stress, and it has been found that it can be used to guide the industrial practice of welding, laser cladding and additive manufacturing. In general, UIT technology shows important potential in metal material processing, which is of great significance for improving material properties and promoting industrial practice.

Chen Z., Ren S., Zhao R., Zhu J., Li X., Zhang H., Lin H., Zhu J., Sohrabi S., Ruan W., Ma J.

Metallic glasses (MGs) possess exceptional properties, but their properties consistently deteriorate over time, thereby resulting in increased complexity in processing. It thus poses a formidable challenge to the forming of long-term aged MGs. Here, we report ultrasonic vibration (UV) loading can lead to large plasticity and strong rejuvenation in significantly aged MGs within 1 s. A large UV-induced plasticity (UVIP) of 80% height reduction can be achieved in LaNiAl MG samples aged at 85% of its glass transition temperature (0.85Tg) for a duration of up to 1 month. The energy threshold required for UVIP monotonously increases with aging time. After the UV loading process, the aged samples show strong rejuvenation, with the relaxation enthalpy even surpassing that of as-cast samples. These findings suggest that UV loading is an effective technique for forming and rejuvenating aged MGs simultaneously, providing an alternative avenue to explore the interplay between the property and microstructures as well as expanding the application prospects of MGs.

Mokashi M., Bhimrao Shirsath A., Çelik A., Lott P., Müller H., Tischer S., Maier L., Bode J., Schlereth D., Scheiff F., Flick D., Bender M., Ehrhardt K., Deutschmann O.

Pyrolysis of hydrocarbon feeds such as methane (CH4) and natural gas emerges as a pivotal carbon dioxide-free large-scale hydrogen (H2) production process combined with capturing the carbon as solid material. For fundamental understanding and upscaling, the complex kinetics and dynamics of this process in technically relevant reactors such as packed and moving beds still need to be explored, particularly concerning carbon formation and its impact on reactor performance. This study integrates kinetic modeling, numerical simulations, and experimental findings to comprehensively understand CH4 pyrolysis under industrially relevant conditions and its implications for efficient H2 production and carbon capture. The investigation covers temperatures from 1273 K to 1873 K, H2 addition with H2:CH4 ratios of 0 to 4, and hot zone residence time of 1 to 7 s. Two distinct pathways lead to carbon formation: soot formation and carbon deposition. Each pathway originates from different gas-phase precursors. An elementary-step-based gas-phase reaction mechanism is coupled with a soot formation model from polycyclic aromatic hydrocarbon and a newly developed deposition model from light hydrocarbons. Numerical simulations are performed in a packed bed reactor model, incorporating a method of moments for soot formation and a model for carbon deposition. The model is evaluated against experiments and predicts the effects of operating conditions on gas-phase product distribution and carbon formation. It also estimates the change in bed-voidage over operational time. The study reveals that at the temperature 1673 K, CH4 conversion exceeds 94 %, while both H2 and solid carbon yields surpass 96 %. The sophisticated modeling and simulation framework presented herein thus provides an enhanced understanding of the CH4 pyrolysis process and presents a valuable tool for optimizing this process.

Diwakar V., Sharma A., Yusufzai M.Z., Vashista M.

Laser cladding is a method of additive manufacturing in which metallic powders or wire are melted and fused onto a substrate using a high-energy laser and create a layer of material with desired thickness and composition which improve the surface properties of the substrate. The estimation of the thermal behavior in the laser cladding is more difficult due to the complex melt pool dynamics which having rapid cooling and solidification of the deposited material on the substrate. However, in laser cladding, involvement of various process parameters and development of the thermal residual stresses during the process affect the mechanical properties of the cladded material. Therefore, it is very important to analyze the process parameters and thermal residual stress to improve the quality of the deposited material. In the simulation, preplaced powder feeding system is used to analyze the effect of the process parameters on the thermal residual stresses. The laser power and scanning speed are critical process parameters which directly affect the amount of heat input into the substrate material. During the parametric simulation, a direct relation was showed between the laser power and temperature distribution but inversely relation is appeared with increasing scanning speed. As the laser power increases, the temperature gradient between the melted material and the substrate material also increases, which corresponds to the development of higher thermal residual stresses in the substrate. However, in case of higher scanning speed, there is less thermal residual stress due to having less time to melt and solidify for deposited material which create less temperature gradient but for the lower scanning speed higher thermal residual stress appeared due to higher heat flux and temperature gradient.