Исследовано сварное соединение из двух титановых пластин, полученное с использованием контактной схемы магнитно-импульсной сварки. Проведен структурный анализ сварного соединения с использованием методов световой микроскопии, растровой электронной микроскопии и микрорентгеноспектрального анализа. Установлено, что процессе сварки скорость соударения пластин непрерывно увеличивается от 450 до 650 м/с, что приводит к постепенному увеличению деформационных и тепловых эффектов. В зонах локального плавления на межслойной границе происходит значительное увеличение твердости. Численное моделирование с использованием метода гидродинамики сглаженных частиц адекватно воспроизводит основные особенности, характерные для магнитно-импульсной сварки, такие как образование струи и локальное плавление на межслойной границе.

Austenitic stainless steels are widely regarded as the perfect choice of structural materials for application in harsh environments and at elevated temperatures. Nevertheless, their operating temperature is limited to 600 degrees C. To further improve the oxidation resistance, protective coatings are applied to their surfaces. In this study, we use nonvacuum electron beam cladding to form on the surface of AISI 321 steel a single-layer NiCrTi-based and a double layer NiCrTiB-based protective coatings. The effect of boron and chromium on microstructure and properties of produced coating was analyzed. The microstructure of the samples was characterized by light microscopy (LM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The properties of the coatings were determined through microhardness measurements and high-temperature oxidation tests. It has been established that cladding a mixture of Ni, Cr, and Ti resulted in the formation of a gamma-Fe solid solution and TiC particles within the coating. The addition of boron and chromium resulted in formation of Cr2B particles on the surface of the coating, which increased its hardness and oxidation resistance. Coatings containing chromium borides demonstrated 3 times higher hardness compared to AISI 321 steel and coatings which didn't contain boron and chromium. Thus, the oxidation resistance of NiCrTiB coatings increased by 4 times due to the formation of dense and continuous Cr2O3-based oxide films that prevented the diffusion of oxygen and ions of metals during the oxidation process.

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.

Non-vacuum electron beam cladding is a highly effective technology for producing protective coatings on metal workpieces. In this study, the 3.8 mm thick TiAl-based coating with Cr and Nb additions was obtained on the Ti alloy substrate in two passes of the electron beam. To evaluate inhomogeneity of the two-layer coating, energydispersive synchrotron X-ray diffraction (EDSXRD) in combination with energy-dispersive X-ray spectroscopy (EDX) was applied. It was found that in the direction from the top of the coating to the substrate, the dilution of the cladding layers with Ti increased. It influenced the phase constitution of the coating and led to a variation in the chemical composition of different phases (alpha 2-Ti3Al, beta-phase, and TiN). The properties of the first (lower) and the second (upper) cladding layers were evaluated separately. The upper layer exhibited greater oxidation resistance than the lower one due to the presence of the gamma-phase, which has superior high-temperature stability compared to the alpha 2-Ti3Al phase, predominant in the coating. The influence of varying chemical composition on the oxidation resistance was also estimated using density functional theory (DFT) simulations. It was found that decrease in Al content in the alpha 2 phase leads to an increase in oxygen absorption energy. This could potentially result in a decrease in oxidation resistance. Wear resistance of the first and the second cladding layers was at the same level mainly due to the low contribution of minor phases. Additionally, DFT simulations show that the variations in chemical composition of the major phase (Ti3Al) are not likely to impact the coating wear resistance.

Multilayer composites formed by explosion welding from alternated plates of niobium and aluminum are studied. The samples are subjected to annealing at 700, 800 and 900°C under a load and without load. The structure, the ultimate tensile strength, the impact toughness and the Vickers microhardness of the composites are determined. It is shown that mixed zones represented by nonequilibrium phases, intermetallic particles of NbAl 3 and Nb 2 Al, and undissolved niobium volumes are formed near “local melting/rapid solidification” interfaces. Increase of the annealing temperature from 700 to 900°C causes growth of the intermetallic inclusions, appearance of cracks in the reaction layer, and considerable worsening of the mechanical properties. The highest ultimate strength (700 MPa) and impact toughness (86 J/cm 2 ) are obtained in the samples annealed under pressure at 900 and 800°C, respectively. Annealing at 700°C at a pressure of 30 MPa is shown to be an optimum treatment producing a favorable effect on the strength characteristics and providing a defect-free structure.

The method of non-vacuum electron beam cladding is used to obtain coatings based on a high-entropy Cantor alloy reinforced with Cr3C2 particles. The microstructure of the coatings is studied; the chemical and phase compositions are determined; microhardness measurements, wear resistance and heat resistance tests are performed. The structure of the coatings is represented by an fcc matrix with Me7C3 carbides. Increase in the percentage of reinforcing particles leads to elevation of the proportion of the carbide phase in the cladding layer. The addition of carbide particles results in growth of the microhardness, wear resistance and oxidation resistance. The structure of the coating obtained from a powder mixture with 50 wt.

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.

Vanadium carbides are known as efficient reinforcing components for surface layers of steel parts. They provide good tribological characteristics of material under sliding friction conditions and against dry abrasive particles. Since wear conditions usually are quite severe, a thick coating is needed to provide the reliable protection of the part. The majority of currently used surfacing technologies ensure the coatings of insufficient thickness. For this reason, the non-vacuum electron beam cladding which is able to provide thick coatings is a reasonable alternative to other surfacing methods. This paper presents an analysis of the microstructure, micro- and nanohardness, elasticity, and tribological characteristics of coatings formed by non-vacuum electron-beam surfacing of vanadium and graphite-containing powder mixtures. In the course of the study, coatings with the average thicknesses of 1.8, 2.5, 2.6, 3.4 mm were formed on the surface of blanks made of medium-carbon steel. Hardness of cladding layers was significantly improved compared to the low-carbon steel (by the factor of 5-7). The wear resistance of coatings under conditions of sliding friction was 5.8 times higher than the wear resistance of the base metal after quenching and tempering; the wear resistance of coatings under conditions of friction against fixed and loosely fixed abrasive particles was -2 and -4.8 times higher, respectively. Surface hardening of steel alloyed with vanadium and carbon derives from the presence of a martensitic matrix, ledeburite precipitates and a high volume fraction (14.5-29.5 vol%) of vanadium carbide particles of a dendritic form, which act as rigid barriers.

Исследованы многослойные композиты, изготовленные cваркой взрывом и состоящие из чередующихся пластин ниобия и алюминия. Проведена термическая обработка полученных образцов — отжиг при 700, 800, 900 °C под нагрузкой и без нее. Определены структура, предел прочности при растяжении, ударная вязкость и микротвердость композитов по Виккерсу. Показано, что вблизи границ раздела, где происходило локальное расплавление и быстрое затвердевание, образовались зоны перемешивания, состоящие из неравновесных фаз, интерметаллидных частиц NbAl3 и Nb2Al, а также нерастворившихся объемов ниобия. Повышение температуры отжига от 700 до 900 °C вызвало рост интерметаллидных включений, что привело к появлению трещин в реакционном слое и значительному ухудшению механических свойств. Наибольшие значения предела прочности (700 МПа) и ударной вязкости (86 Дж/см2 ) образцов получены после отжига под давлением при 900 и 800 °C соответственно. Оптимальным режимом, благоприятно влияющим на прочностные характеристики и способствующим сохранению бездефектной структуры, является отжиг при 700 °C под давлением 30 МПа.

Three-layer composite materials composed of VT1-0 alloy plates and an amorphous layer of ST15 alloy between them, which were produced by magnetic pulse welding, have been studied. The structure of the composites was studied by scanning and transmission electron microscopy. The phase composition was determined using x-ray synchrotron radiation and electron diffraction. It is shown that the welding process causes partial remelting of the amorphous ribbon and its mixing with titanium, and the cooling causes re-amorphization. Titanium interacts with atmospheric gases and forms oxides and nitrides, which are distributed in the remelted zones of the amorphous layer in the form of particles not larger than 35 nm in size. Welding of the amorphous ribbon to the less active nickel does not produce additional phases.

Исследованы трехслойные композиционные материалы, состоящие из пластин ВТ1-0 и аморфного слоя из сплава СТ15 между ними, полученные методом магнитно-импульсной сварки. Изучена структура сформированных материалов методами растровой и просвечивающей электронной микроскопии. Определен фазовый состав композитов с использованием рентгеновского синхротронного излучения и дифракции электронов. Показано, что в процессе сварки аморфная лента подвергалась частичному переплаву и перемешиванию с титаном, а при охлаждении — повторной аморфизации. Титан, взаимодействуя с газами атмосферы, формировал оксиды и нитриды, которые распределялись в зонах переплава аморфного слоя в виде частиц размером не более 35 нм. При сварке аморфной ленты с менее активным никелем не наблюдалось образования дополнительных фаз.

Ti-Al3Ti metal-intermetallic laminate (MIL) composites are known as promising structural materials due to the unique combination of their specific properties. However, their application is still limited due to the extremely high brittleness of the Al3Ti phase. In this study, we attempt to address this issue by changing the D022 crystal structure of Al3Ti to the more ductile L12 structure by alloying it with silver. To select the best fabrication regimes of Ti-Ti(Al1-xAgx)3 composites, in situ synchrotron X-ray diffraction analysis was performed to reveal the chemical reactions occurring upon heating the Ti-Al-Ag sample. The analysis showed that the highest amount of Ti(Al1-xAgx)3 phase with the L12 structure appears at 930 degrees C. This temperature was chosen for subsequent spark plasma sintering experiments. Scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction analysis revealed that the sintered sample consisted mainly of Ti, Ti(Al1-xAgx)3, and a minor fraction of the Ag-Al compound distributed in the central parts of the intermetallic layers and at the grain boundaries. Modification of the titanium trialuminide crystal structure positively affected the properties of the composite, providing a 60% increase in fracture toughness. The Ag-Al phase also contributed to toughening, causing an additional crack deflection effect. (c) 2022 Published by Elsevier B.V.

Due to low thermal stability and limited critical size, metallic glasses (MGs) are frequently considered for reinforcing composites. The production technology of composites should provide the minimum heat input to preserve the disordered structure of MGs. In this study, the solid-state magnetic pulse welding (MPW) was used to join crystalline titanium and Ti-based MG. The amorphous structure of the MG layer after MPW was confirmed by synchrotron X-ray radiation diffraction (XRD), ultra-small-angle X-ray scattering (uSAXS), and transmission electron microscopy (TEM). Crystalline particles were found only in the mixing zones subjected to the strongest heating during welding. The average size of the crystalline precipitates was about 25 nm, and their phase composition corresponded to a-Ti. In addition to Ti particles, titanium oxides and nitrides could form at the interface of Ti and MG layers during MPW.

Layered metallic-intermetallic composites formed by explosion welding of nickel and aluminum plates and subsequent annealing of the bimetal for 1 – 100 h at 550, 570, 590 and 610°C are studied. X-ray diffraction analysis is used to determine special features of the structure of interfaces of bimetallic billets after welding and to estimate their contribution into the processes of nucleation and growth of layers of nickel aluminide. It is shown that the formation of the intermetallic is determined primarily by volume diffusion. The activation energy of the growth of the nickel aluminide layer depends on the structural state of the diffusion pair and on the presence of oxide films on the interfaces of the metallic plates.

Исследованы слоистые металл-интерметаллидные композиты, сформированные методом сварки взрывом пластин никеля и алюминия и последующего отжига полученного биметалла в течение 1 - 100 ч при 550, 570, 590 и 610 °C. Методами структурного анализа выявлены особенности строения границ раздела биметаллических заготовок после сварки и проведена оценка их вклада в процессы зарождения и роста интерметаллидных фаз. Проанализирована кинетика роста прослоек алюминида никеля. Установлено, что формирование интерметаллида определяется преимущественно объемной диффузией. Показано, что энергия активации роста слоя алюминида никеля зависит от структурного состояния диффузионной пары и наличия на границах раздела металлических пластин оксидных пленок.

Non-vacuum electron beam cladding was applied to obtain CoCrCuFeNi cladding layers with thicknesses of 0.89 and 1.24 mm on a surface of mild steel. The cladding layers possessed the dendritic structure. Interdendritic space was filled with a Cu-rich phase. It was found by X-ray diffraction analysis that FCC solid solution phases were formed during crystallization. The lattice parameter of the dendritic phase was a=3.59 Å, while that of the interdendritic phase was equal to a=3.60 Å. The average microhardness values of the cladding layers were lower compared to the base material and equaled 156 HV and 190 HV.

In the present study the thin NiAl intermetallic foils formed on different types of substrates by magnetron sputtering technique were investigated. To provide the deposition of intermetallic NiAl compound in one step without additional heat treatment the composite targets assembled from parts of Al and Al plates were used. The structure of formed thin NiAl coatings was studied using scanning electron microscopy and X-ray diffraction analysis. Mechanical properties were assessed by nanohardness indentation and wear testing of deposited coatings. During sputtering the distance from the target to the substrates varied from 60 to 100 mm to estimate the effect of this parameter on structure and properties of the coatings. The results revealed that thin coatings sputtered at the closer distance from the target to the substrates had the higher hardness about 11 GPa and exhibited the high level of wear properties.

In this study, we describe an experimental setup and a new approach for operando investigation of structural evolution of materials during wear and friction. The setup is particularly suited for testing various friction pairs, including those in which both rubbing bodies are made of metals. The developed device allows circumventing the problems related to significant scattering of X-rays produced by metals and makes it possible using “real samples” in synchrotron beamlines operating in reflection mode. To demonstrate the capabilities of the device and the proposed new approach, an iron-based massive sample was subjected to thousands of friction cycles using a cemented carbide pin. The material was probed with synchrotron X-ray radiation within a few milliseconds after leaving the friction zone. The results of the microstructural and structural analysis, as well as results obtained from diverse mathematical models, allowed us to evaluate several features, including gradual accumulation of defects, microstructural refinement, dislocation density changes, surface layer oxidation, as well as several other phenomena caused by the dry sliding friction process. Mainly, it was possible to conclude that the process of wear occurred due to the cooperative action of oxidation and plastic deformation, which began during the first cycle of frictional interaction and was manifested in increasing the dislocation density, whose type was changed gradually during testing. The number of defects quickly reached a threshold value and subsequently fluctuated around it due to periodically repeated processes of defect accumulation and stress relaxation resulting from material wear. It was also observed that friction led to the quick formation of a mechanically mixed layer, consisting of the sample material and a mixture of two types of iron oxide – hematite and magnetite. The delamination of this layer was probably the primary wear mechanism.