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A relatively new approach to obtaining metal materials containing several principal elements in equiatomic concentrations which look promising for replacing commercially used alloys is proposed. Such materials are called high-entropy alloys (HEAs). Studies show that HEAs tend to form a simple solid-solution structure and can also contain ordered intermetallic phases. Such a method of forming metal materials can be regarded as a background for producing new HEAs with elevated performance characteristics. Most studies focus on the relationship between microstructure and measured properties; significantly less attention is paid to studying and developing new effective methods for creating HEAs. In this paper, we study the possibility of obtaining CoCrFeNiMn–(X) HEAs by centrifugal metallothermic SHS. Chemical and technological modes of modifying cast CoCrFeNiMn alloy during synthesis (in situ) by introducing alloying components into the starting exothermic compositions are tested for the first time. The microstructure and phase composition of NiCrCoFeMn alloys synthesized from mixtures containing Ti–Si–B(C) or Al are characterized. The microstructure of CoCrFeNiMn–(Ti–Si–B(C)) HEAs is found to consist of an HEA-based matrix and new structural inclusions of carbides and borides of titanium. High-Al CoCrFeNiMn–Al HEAs are represented by a composite structure containing NiAl as a basis and dispersion nanoprecipitates (~100 nm) of a Cr- and Fe-based solid solution.

A comprehensive comparative study of the structure, phase composition, and mechanical properties of heat-resistant nickel-based Ni–Cr–(X) alloys produced by the methods of traditional metallurgy and self-propagating high-temperature synthesis (SHS metallurgy) is carried out. With the purpose of formation of the submicrocrystalline structure, a longitudinal rolling and post-deformation annealing of the cast alloy is performed. The microstructure of the heat-resistant alloys is investigated by the SEM and TEM methods. It is shown that the cast alloy has a recrystallized structure with the mean grain size of ~1 μm and the particles of chromium carbides have a size of ~1–3 μm. After rolling and subsequent annealing (750°C/1 h), the average grain size is reduced to 0.43 μm and the formation of dispersed particles of carbides 100 nm in size is observed. The structure of the alloy obtained by SHS metallurgy is dendritic, and particles of W and Cr are absent. When 0.1 wt % carbon powder is added to the initial powder mixture for SHS synthesis, formation of the network of W and Cr particles is observed along the boundaries of dendrite colonies. It is found that the SHS Ni-based heat-resistant alloy similar in composition to commercial cast alloy is characterized by improved mechanical properties and increased heat resistance compared to the cast alloy in both the coarse-grained and the submicrocrystalline state. Adding the carbon powder to the powder mixture for SHS leads to a further increase in the resistance to high-temperature deformation owing to formation of the carbide phase impeding the movement of dislocations and grain boundary creeping processes.

The laws and mechanism of combustion of TiO2 based thermite systems with a complex reducing agent (Al and Ca) under the influence of overload are revealed. The thermite system includes a basic composition whose combustion products are target elements (Ti, Al, Nb, and Cr) and a high-energy additive (CaO2, Al, and Ca) for ensuring high-temperature combustion. With the introduction of an energy additive, the system acquires the ability to burn. With a sufficient content of this additive, the combustion products (TixAly and Al2O3 and CaO oxide solutions) can melt. As the fraction of Ca in the base mixture composition increases, the burning rate drops and the reduction completeness of the target oxides increases. With an optimal ratio of Ca and Al in the mixture, the yield of the target elements in the ingot is close to the calculated value.

TiAl-based composite materials have been produced by spin-casting self-propagating high-temperature synthesis metallurgy methods using thermite-type mixtures, general relationships in the formation of their composition and structure have been investigated, the synthesis conditions have been optimized, a method for obtaining large ingots has been proposed, and their composition and structure have been determined. We have obtained cast Nb- and Cr-doped TiAl-based composite materials using mixtures of Ti, Nb, Cr, and Ca oxides with a combined reducing agent (Al and Ca) under the effect of an overload above 200g. It has been shown that partial Ca substitution for Al in the starting mixture ensures complete reduction of the TiO2, and the resultant metallic phase contains calculated amounts of Ti and Al. Mixtures of optimized composition make it possible to produce a cast composite material similar in composition to alloy 4822.

Mo-Ni-B-Al as-cast alloys containing 35.5-58.7 wt% Mo, 23.0-57.6 wt% Ni, 3.3-5.2 wt% B, and 2.2-13.5 wt% Al were synthesized by Self-Propagating High-Temperature Synthesis (SHS) using a mixture of MoO3, NiO, B2O3 and Al powders in order to obtain low-cost Mo2 NiB2 containing hard materials. The first series of experiments were performed using 1.05 times the stoichiometric amount of Al. In the second series of experiments, FactSage thermochemical modeling software was used to minimize Al increasing the Mo2NiB2 formation in the as-cast alloys. The products were characterized by using atomic absorption spectrometry (AAS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and micro-hardness techniques.

Laser beam welding and friction stir welding of high entropy alloys (HEA) of the CoCrFeNiMn system were studied. The HEAs were produced by self-propagating high-temperature synthesis (SHS). Along with the principal elements, Al, C, S, and Si impurities were detected in the composition of the alloys. The as-cast alloys consisted of columnar fcc grains with coarse precipitates of MnS and fine Cr-rich M23C6carbides. Laser beam welding resulted in the formation of a defect-free weld joint. Precipitation of nanoscale B2 phase particles in the weld zone leaded to a pronounced increase in microhardness from ~150 HV of the base material to ~220 HV in the fusion zone. Friction stir welding (FSW) of a recrystallized state of the HEA with the average grain size of 3-5 μm resulted in the formation of a fine microstructure with a grain size of ~1.5 μm in the most strained area. Noticeable rise in strength and some decrease in ductility of the processed alloy in comparison with the initial condition can be associated with the formation of nanosized M23C6carbides.

In this paper, we report microstructure and mechanical properties evolution of the CoCrFeNiMn-type high entropy alloy, containing small amounts of Al and C, during cold rolling and subsequent annealing at 700-1100°C. In the initial as-cast condition the alloy has coarse-grained single face-centered cubic (fcc) phase structure. Cold rolling and annealing substantially refine fcc grains; in addition M23C6 type carbides appear. After annealing at relatively low temperatures (≤900°C), these particles are arranged in characteristic arrays aligned with rolling directions. The specific microstructure of the thermomechanically processed alloy is suggested to be the reason of the balanced combination of tensile strength and ductility.

Butt-joint seam of a high entropy alloy (HEA) of the CoCrFeNiMn system was successfully obtained by friction stir welding (FSW). The HEA was produced by self-propagating high-temperature synthesis. Along with the principal elements, a small amount (0.9 at.%) of C was added to the alloy. The as-cast alloy was cold rolled and annealed at 900 °C to produce refined microstructure. The structure of the annealed alloy consisted of a recrystallized face-centered cubic matrix with a grain size of 9.2 μm and fine Cr-rich M23C6 carbides. FSW of the HEA resulted in microstructure refinement to d = 4.6 μm in the stir zone. A noticeable rise in strength and some decrease in ductility of the processed alloy in comparison with the initial condition can be associated with the microstructure refinement and some increase in the volume fraction of M23C6 carbides.

A new approach to increase the tensile performance of high entropy alloys (HEAs) by producing a duplex ultrafine-grained (UFG) structure was reported in this work. A novel HEA based on the CoCrFeNiMn system with substantial amounts of Al and C was used for the illustration of this approach. In the as-cast condition the alloy had almost entirely a single face-centered cubic (fcc) phase structure with an insignificant amount of M23C6 carbides. After cold rolling and annealing at 800–1000 °C an increased amount of fine second phases, namely M23C6 carbides and B2 phase, effectively pinned boundaries of recrystallized fcc grains. As a result, a duplex UFG structure composed of the recrystallized fcc grains and M23C6 and B2 particles was produced. The alloy with the UFG structure demonstrated attractive mechanical properties. For example, after annealing at 900 °C the alloy had the yield strength of 785 MPa, the ultimate tensile strength of 985 MPa, and elongation to fracture of 32%. The phase composition of the alloy in different conditions was compared with the equilibrium phase diagram obtained using a Thermo-Calc software. Strengthening mechanisms were qualitatively analyzed, and some possibilities for further improvement of strength of the alloy were discussed.

Fiber laser beam welding of a CoCrFeNiMn-type high entropy alloy (HEA) produced by self-propagating high-temperature synthesis (SHS) was reported in this work. The SHS-fabricated alloy was characterized by both ∼2 times reduced Mn content in comparison with that of the other principal components and the presence of impurities including Al, C, S, and Si. The as-fabricated alloy was composed of columnar fcc grains with coarse precipitates of MnS and fine Cr-rich M23C6 carbides. Successful defect-free butt joint of the alloy was obtained using a laser power of 2 kW and a welding speed of 5 m/min. Welding resulted in changes in texture and structure of the fcc matrix. In addition, precipitation of nanoscale B2 phase particles in the weld zone was observed. A pronounced increase in microhardness from (153 ± 3) HV 0.5 (base material) to (208 ± 6) HV 0.5 (fusion zone) was observed. The B2 phase precipitation after welding was found to be in a reasonable agreement with the ThermoCalc predictions. Quantitative analysis demonstrated that the increase in hardness can be associated with the B2 phase precipitation. Possibilities of the development of HEAs with intrinsic hardening ability after laser processing are discussed.

Composite materials (CMs) based on niobium with functional and alloying additives (Si, Hf, Ti, Al, etc.) have prospects for industrial approval in aviation propulsion engineering. The authors previously showed that such CMs can be synthesized in an autowave mode (combustion mode) using highly exothermic mixtures of Nb2O5 with Al, Si, Hf, and Ti. It was found that hafnium actively participates in the reduction of Nb2O5, which complicates its introduction into the CM. This study is directed at investigating the possibility to synthesize Nb-based composite materials with a high Hf content using methods of centrifugal SHS metallurgy. It is shown in experimental investigations using a centrifugal installation under the effect of acceleration of 40 g that the replacement of active Hf by its less active compounds Hf–Al or Hf–Ti–Si–Al in the composition of the Nb2O5/Al mixtures makes it possible to transfer the combustion of the mixture from the explosion-like mode into the steady-state combustion mode. The content of Hf in the CM increases with an increase in the size of Hf–Al granules from 0–40 to 160–300 μm from 1.3 to 3.8 wt %. The introduction of Hf–Ti–Si–Al granules with a particle size from 1 to 3 mm into the initial charge makes it possible to form cast CMs based on niobium silicides with a Hf content up to 8.1 wt %. The integral composition and distribution of base and impurity elements in structure components of cast CMs, as well as their phase composition, were determined using electron microscopy and X-ray phase analysis. CMs with the maximal Hf content (8.1 wt %) contain three structural components: (1) the base, which includes Nb, Si, and Ti; (2) intergrain boundaries containing Nb, Ti, and Al; and (3) inclusions based on hafnium oxide. Three phases are revealed in the X-ray diffraction pattern of the CM, notably, solid solutions based on Nb and Nb5Si3, as well as a minor amount of Nb3Si.

The production of hafnium aluminides from mixtures of hafnium or its oxide with aluminum in the combustion mode is impossible because of a near-zero thermal effect. The present study is aimed at stimulating autowave chemical transformation with the help of energetic formulations and producing cast hafnium aluminides by means of combustion methods. The characteristics of the autowave synthesis and the conditions for producing cast hafnium aluminides are determined, and their composition and structure are investigated.

Composite materials based on Nb with functional (Si, C, B) and alloying dopants (Hf, Ti, Al, etc.) are promising materials for aircraft engine applications. Our previous studies have shown that such composites can be synthesized in the autowave mode (combustion mode) using highly exothermic mixtures of Nb2O5 with Al, Si, Hf, and Ti. It has been found that in the combustion wave, Hf actively participates in the reduction of Nb2O5, which complicates its introduction into the composite material and leads to an excess of Al in the alloy. In the present study, we investigated the possibility of replacing Hf in the starting mixture by less active HfAl3 and also determined the effect of the grain size of HfAl3 on the Hf content in the composite material.

The combustion and chemical transformation of highly exothermic MoO3/NiO/Al/C andMoO3/NiO/Al/B mixtures on the surface of a titanium substrate under centrifugal acceleration are studied. It is shown that chemical reactions occur not only in the combustion wave, but also on the surface of the titanium substrate, between the combustion products and the substrate material (titanium). The dynamics and mechanism of formation of layered (gradient) titanium–ceramics materials (Mo–Ni–C–Ti or Mo–Ni–B–Ti) is investigated.

This work is focused on preparation of Nb-doped Ti–Al material (Ti–29.3Al–17.6Nb wt %) by centrifugal SHS. Results of studying of combustion and synthesis regularities of intermetallic material on γ-TiAl base from oxide materials under high gravity are presented in the article. For the first time is used a reduction mixture on Al/Ca base which markedly increases the yield of Ti–Al–Nb and decreases the amount of non-metallic impurities (oxygen, nitrogen, carbon) in target product.

The review of the results obtained by the authors in synthesis of cast composite materials by the methods of SHS metallurgy is made. The main attention is paid to synthesis of heat-resistant materials based on intermetallic compounds of nickel and titanium and niobium silicides as well as tungsten-free hard alloys based on titanium and chromium carbides. The parameters allowing one to govern the process, material structure and composition were determined. Practical application was specified.

The structure and mechanical behavior of NiAl-based intermetallic alloys alloyed with Hf, Cr and Co at their total content (Cr+Co)=18 at% were studied. The alloys were prepared by centrifugal SHS casting from oxide raw materials. The mechanism of precipitation hardening is shown to take place at the Cr/Co ratios >0.5, leading to the formation of chromium-based inclusions and nanosized precipitates in the NiAl dendrite body. The resulting alloys have a three-level hierarchical structure with oxygen, nitrogen, and carbon impurity contents of 0.129, 0.0045, and 0.04 wt%, respectively, and the ultimate compressive strength at room temperature equal to 2300 MPa.

The structure and mechanical properties of the Ni41Al41Cr12Co6 intermetallic alloy prepared by vacuum induction remelting (VIR) of the SHS semi-product are studied. The evolution of the microstructure of the Ni41Al41Cr12Co6 alloy heated in the temperature range of 20–850 °C was investigated. Noticeable dissolution of Cr inclusions at temperatures above 550 °C is observed; the dissolution stage is preceded by fragmentation of dispersed Cr inclusions into nanocrystallites. The thermomechanical properties of the Ni41Al41Cr12Co6 alloy were determined in the temperature range of 400–1100 °C. VIR is found to increase high-temperature creep resistance and thermal stability of the Ni41Al41Cr12Co6 alloy to a certain extent.

SHS-produced complex intermetallics were used as precursors for preparation of Ni–Fe- and Cobased catalysts for deep oxidation of carbon monoxide, propane, and hydrogen. The catalysts were characterized by XRD, SEM, EDS, and BET method and revealed a developed nanostructured surface, which explains their high activity in the processes of deep oxidation. The catalysts under study look promising for incineration of waste and exhaust gases, safeguarding fire/explosion hazards, as well as for use in flameless heat generation, fuel cells, etc.

The gravity-assisted combustion synthesis of γ-TiAl from oxide raw materials by using Al–Ca mixture as a reductant was explored. The use of Al–Ca reductant markedly increased the yield of TiAl and decreased the amount of residual contaminants (such as oxygen, nitrogen, carbon) in target product.

The NiAl–Cr–Co–X alloys were produced by centrifugal self-propagating high-temperature synthesis (SHS) casting. The effects of dopants X = La, Mo, Zr, Ta, and Re on combustion, as well as the phase composition, structure, and properties of the resulting cast alloys, have been studied. The greatest improvement in overall properties was achieved when the alloys were co-doped with 15% Mo and 1.5% Re. By forming a ductile matrix, molybdenum enhanced strength characteristics up to the values σucs = 1604 ± 80 MPa, σys = 1520 ± 80 MPa, and εpd = 0.79%, while annealing at T = 1250 ℃ and t = 180 min improved strength characteristics to the following level: σucs = 1800 ± 80 MPa, σys = 1670 ± 80 MPa, and εpd = 1.58%. Rhenium modified the structure of the alloy and further improved its properties. The mechanical properties of the NiAl, ZrNi5, Ni0.92Ta0.08, (Al,Ta)Ni3, and Al(Re,Ni)3 phases were determined by nanoindentation. The three-level hierarchical structure of the NiAl–Cr–Co+15%Mo alloy was identified. The optimal plasma treatment regime was identified, and narrow-fraction powders (fraction 8–27 µm) characterized by 95% degree of spheroidization and the content of nanosized fraction

The first positive experience in synthesis of cast high-entropy alloys in the combustion mode, referred to as SHS metallurgy (SHS is self-propagating high-temperature synthesis) has been reported. Analysis of the data obtained enables the conclusion that the one-stage SHS method is promising for the production of cast metal materials using a new principle of formation of high-entropy polymetallic alloys.

NiAl-based electrodes of a required size were fabricated by combined use of centrifugal SHS casting and induction remelting in an inert atmosphere and characterized by modern analytical methods. Thus produced electrode materials exhibiting high chemical purity and low content of impurity gases (0.005 wt % O, 0.0001 wt % N) can be recommended for use in centrifugal plasma sputtering of micro granules via the plasma rotating electrode process (PREP).

Highly caloric mixtures of metal oxides with reducing agents used in SHS metallurgy can burn at combustion temperatures well above the melting point of final products, which ensures formation of cast products. The data of basic research in the field allowed us to suggest methods for manufacturing new cast nickel aluminides based alloy.

A new class of highly active polymetallic catalysts for deep oxidation based on iron with admixtures of other d-metals and rare earths has been developed. The precursors of the catalysts are multicomponent intermetallides obtained by selfpropagating high-temperature synthesis (SHS). The XPA spectra, specific surface, and the morphology of the surface according to the SEM results are studied. The catalytic properties are studied using the example of deep oxidation processes of carbon monoxide and propane. It has been shown that two-level metal–oxide nanostructures are common features of the surface for the catalysts studied. The lowest level represents granules 10–30 nm in diameter, of which flat hexahedrons are built with a diameter of about 1 μm and a thickness of ≤100 nm.

We have studied general relationships in the fabrication of niobium silicide-based composite materials by self-propagating high-temperature synthesis in combination with spin casting, using thermite mixtures. Cast Nb–Si–Hf–Ti–Al and Nb–Si–Hf–Ti–Al–Cr materials with a composite structure have been obtained. Models have been proposed for chemical transformations in a combustion wave and the formation of a cast material in several steps.

A Co–Cr–Mo alloy was produced by centrifugal SHS and its fine structure, elemental maps, defect structure, and orientation relationships between the constituent phases were characterized by highresolution TEM.

The technique of centrifugal SHS was used to fabricate an alloy with a composition close that of commercially available alloy 48Ti–48Al–2Nb–2Cr by using Ti–Al–Nb2O5–Cr2O3–CaO2 thermite mixtures. The synthesized alloy exhibited a uniform structure and a composition close to that of commercial prototype. Its main drawback is the presence of undesired admixtures of O, N, P, Ca, C, and Si. Further efforts should be oriented on diminishing a contamination level.

A Co–Cr–Mo alloy with homogenous ultrafine-grained structure prepared by combined use of metallothermic SHS and subsequent thermomechanical treatment (TMT) was characterized by SEM and XRD and the processing conditions were optimized.

A complex manufacturing method of billets from material based on high-boron nickel aluminide is proposed. The method includes manufacturing the semifinished alloy products using a combined method of self-propagating high-temperature synthesis and centrifugal casting from oxide feedstock and subsequent vacuum induction remelting with the introduction of Al-based foundry alloys containing nanosized ZrO2 and modifying the structure. The evolution of the microstructure and phase composition is investigated at all production stages. A cast ZrO2-modified cylindrical billet, which possess high purity in regards to gas impurities (O 0.005 wt % and N 0.0001 wt %) and is suitable for the further production of powders by the plasma rotating electrode process, is fabricated according to the proposed technology.

The synthesis, physicochemical characteristics, and operation of the previously proposed new multifunctional polymetallic catalysts in reduction processes are considered. The complex intermetallides of 3d metals and rare-earth elements, which are obtained by self-propagating high-temperature synthesis (SHS), are catalyst precursors. The catalyst structure includes a framework of lower intermetallic compounds covered with a strongly disordered highly amorphous metal oxide active phase. This phase forms two-level nanostructures (~10–100 nm) with a characteristic shape of flat hexahedrons on the surface. The catalysts possess high activity in the reactions of deep oxidation and reduction (the Fischer–Tropsch synthesis and the hydrodesulfurization of petroleum fractions); moreover, they do not require preliminary activation in the reduction processes.

Cast Mo2NiB2–Ni metal-matrix composites and protective coatings thereof were fabricated by centrifugal metallothermic SHS process. The quality of SHS surfacing was found to depend on process parameters such as the mass of green mixture per unit surface area of substrate and centrifugal acceleration. The hardness of synthesized coatings was rather high and attained as large values as 800–1200 H V. Optimal conditions for deposition of high-quality protective coatings onto a steel substrate were found experimentally. The process can be recommended for practical implementation in production of cutting tools, tribological materials, molds, and deposition of protective coatings. The present results can be expected to make a theoretical background for industrial-scale manufacturing of new tungsten-free MMCs and protective coatings with valued service parameters.

The effect of cold rolling on the microstructure and mechanical properties of an Al- and C-containing CoCrFeNiMn-type high-entropy alloy was reported. The alloy with a chemical composition (at %) of (20–23) Co, Cr, Fe, and Ni; 8.82 Mn; 3.37 Al; and 0.69 C was produced by self-propagating high-temperature synthesis with subsequent induction. In the initial as-cast condition the alloy had an face centered cubic single-phase coarse-grained structure. Microstructure evolution was mostly associated with either planar dislocation glide at relatively low deformation during rolling (up to 20%) or deformation twinning and shear banding at higher strain. After 80% reduction, a heavily deformed twinned/subgrained structure was observed. A comparison with the equiatomic CoCrFeNiMn alloy revealed higher dislocation density at all stages of cold rolling and later onset of deformation twinning that was attributed to a stacking fault energy increase in the program alloy; this assumption was confirmed by calculations. In the initial as-cast condition the alloy had low yield strength of 210 MPa with yet very high uniform elongation of 74%. After 80% rolling, yield strength approached 1310 MPa while uniform elongation decreased to 1.3%. Substructure strengthening was found to be dominated at low rolling reductions (

Cast nickel aluminide-based eutectic alloys of the equimolar composition NiAl-Mo (Cr, V, Nb) alloyed with boron and hafnium are fabricated by centrifugal SHS metallurgy. It is established experimentally that the acceleration range of 150–200 g is the most manufacturable. It is shown that the convective motion of the melt behind the combustion front under the effect of gravitation leads to an increase in the combustion rate, completeness of the chemical interaction in the combustion wave, and composition homogenization of combustion products over the melt bulk. It is established that alloys have the homogeneous composite structure of the NiAl grain with an insignificant amount of boride inclusions (MoB, V(Cr)B, Mo(Nb)B2), which are uniformly distributed in the matrix consisting of the β/γ eutectics. The density for all four compositions under study did not exceed 6.7 g/cm2.

Cast NiAl/Ni20Al3B6 composites containing 2.3–3.5 wt % B have been prepared by centrifugal SHS for the first time. The composite materials comprised of a solid-solution matrix based on NiAl with inclusions of Ni20Al3B6 and complex boride (Mo, Cr)B. Best results were achieved at centrifugal accelerations 150–200 g in open air. Cast materials based on NiAl and τ-borides seem promising for use in turbine power units.

Mo2NiB2 and Mo2FeB2 metal-matrix composites (MMCs) were prepared by metallothermic SHS in a centrifugal machine. Our SEM and XRD data suggest that thus synthesized cast materials represent a ductile Ni or Co matrix doped with uniformly distributed inclusions of Mo2NiB2 or W2CoB2 particles. The metal matrix was found to contain grid-type structural elements formed by nickel aluminides. Addition of alloying agents into a green mixture was found to markedly change the microstructure and morphology of resultant MMCs. The Vickers hardness of synthesized MMCs was found to vary between 950 and 1200 HV.

It is shown that critical conditions (temperature and pressure) in a fuel cell (metal tube piece) of a model nuclear reactor can be produced by burning energetic thermite SHS systems. The heating temperature of the zirconium or steel tube can be controlled by varying the composition of the thermite mixture, the gap between the thermite pellet and the tube wall, and the design of the thermite pellet. The results of the studies show that a WO3-2Al based thermite mixture can be used to model an emergency situation (without the use of radioactive fuel) in the reactor fuel cell.

Laser beam welding was used to produce butt joints from the CoCrFeNiMn-type high entropy alloy. The alloy in the initial condition had an fcc single-phase coarse-grained structure. Laser welding resulted in the M7C3-type carbides precipitation in the fcc matrix. The carbide particles precipitation resulted in a considerable increase in microhardness from 150 HV 0.5 for the as-sintered condition to 205 HV 0.5 in the fusion zone. Laser beam welding had a negligible effect on both static mechanical properties and fatigue behaviour of the alloy. The endurance limit of either type of specimens (i.e. with and without welding seam) was 200 MPa. Fracture of all specimens with the laser beam welded seams occurred in the base material area during both tensile and fatigue testing. Weak effect of welding on static/fatigue behaviour of the alloy can be attributed to the higher hardness of the fusion zone, resulting in strain localization in the base material area. An increase in load resulted in activation of secondary slip systems and formation of deformation twins in fatigue specimens.

A novel high entropy alloy based on the CoCrFeMnNi system with substantial amounts of Al and C was studied. After cold rolling and annealing at 973-1273 K a duplex ultra-fine grained structure composed of the recrystallized fcc grains and M23C6 and B2 particles was produced. Analysis of the coarsening behavior of grains and particles growth suggested that kinetics of both was controlled by volume diffusion. The apparent activation energy of structure coarsening during recrystallization was evaluated.

In the present study, the active phases (AP) of an Fe–Ni–Co–Mn catalyst produced from SHS-intermetallics (a), a catalyst prepared via formation an intermetallic layer on a mesh surface of chromium-nickel stainless steel (b), and of a Co–Mn catalyst prepared via SHS on silica gel support (c), were isolated and characterized by SEM and XRD. The catalysts studied were highly active in the process of deep oxidation and catalysts (b) and (c) were highly active in the process of CO2 methanation as well. All AP had oxo-metallic composition and were formed from nanoscale components, but if the structure of these components for catalyst (a) was the same as on the surface of the catalyst, the structures of AP components for catalyst (b) significantly differed from the surface structures. In addition, AP sediment grain nanostructures of catalyst (c) differed from those of catalysts (a) and (b).

The possibility of utilizing the industrial wastes of the metallurgical production and secondary raw materials (aluminum) by organizing self-propagating high-temperature synthesis (SHS) and obtaining metal pipes with an inner ceramic coating is investigated. The main production operations of the preliminary preparation of the starting raw materials are worked out and functional coatings providing high abrasive resistance are revealed. The results of testing the samples showed that the durability of the pipes with the deposited coating increases by a factor of more than 20. The possibility of forming highly energy-effective SHS technology of processing the industrial wastes of metallurgical production and obtaining pipes with a high abrasive resistance is shown.

Combination in one process of SHS and metallothermy, called SHS metallurgy. Polymetallic alloys with uniform distributed components throughout the volume. Does not allow full control of the formation of the microstructure during crystallization and cooling. Interest in SMC and NS metallic materials is due to their unique physicochemical and mechanical properties, which are substantially different from those of conventional coarse-grained materials. Because of the universality of SHS synthesis, using it enables the production of modern medical alloys that meet the highest requirements for biochemical and biomechanical compatibility.