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The paper presents the results of the X-ray diffraction analysis, scanning electron microscopy, and electron probe micro-analysis of the products synthesized from the titanium, carbon (soot), and aluminum powder compositions in the wave combustion mode. It is found that the carbon/aluminum ratio in the reactive powder compositions has an effect on the combustion temperature, phase composition, and structure of the synthesis products. The major phase in the synthesis products is titanium carbide with the particle size monotonically decreasing in the composite structure with decreasing carbon/aluminum ratio in the reactive powder compositions resulting from the reduction in the combustion temperature. Based on the structural investigations of the synthesized composites, their practical application as feedstocks is discussed in relation to the coating deposition and cladding, and as bulk materials consolidated via hot isostatic pressing or spark plasma sintering.

—Fe 2 Ti and FeTi intermetallic compounds are of practical use as either hydrogen storages (FeTi) or magnetic materials (Fe 2 Ti). Owing to features of the equilibrium binary phase diagram, the preparation of the intermetallics by casting is difficult. Therefore, powder metallurgy methods along with preliminary mechanical activation of powder mixtures are widely used. The aim of the study is to investigate the possibility of preparation of single-phase compounds from titanium and iron powder mixtures having target compositions. Mechanically activated powder mixtures and products of combustion and subsequent annealing are studied by X-ray diffraction analysis, optical metallography, and scanning electron microscopy and energy dispersive spectroscopy used for the determination of the element composition. Powder mixtures are subjected to 20‑min mechanoactivation in an Activator 2S planetary mill at an intensity of 40 g ; the ball-to-mixture ratio is 20. The mechanically activated mixtures are heated in a hermetically sealed reactor in an argon atmosphere at an average rate of 85 deg/min. Thermal curves, which are measured with thermocouples placed into a mechanoactivated mixture, demonstrate an abrupt rise (thermal explosion (TE)), which corresponds ~500°C and indicates the occurrence of an exothermic reaction in the mixture. The 2Fe + Ti composition is found to indicate the substantially higher rise as compared to that observed for the Fe + Ti composition. X-ray diffraction analysis shows that the Fe 2 Ti compound is the main reaction product for the both mixtures. The dominant formation of Fe 2 Ti and the high thermal effect of the 2Fe + Ti mixture as well are explained by the higher negative enthalpy of formation of Fe 2 Ti as compared to that of FeTi (–87.45 and –40.58 kcal/mol, respectively). High temperature homogenizing annealing of TE products results in the formation of a double-phase target product. After annealing, the contents of side phases and unreacted reagents slightly change. Based on the obtained data, it is inferred that the thermodynamic factor (enthalpy of formation of intermetallic) is the main factor determining the phase composition of the synthesis products in titanium and iron powder mixtures.

Using the method of hot compaction (HC) of mechanically activated powder mixtures of titanium and carbon (carbon black) in an ethanol medium, titanium-matrix composites with a carbide strengthening phase were obtained. To obtain a composite with different content of titanium carbide, the amount of carbon was varied within the range of 0–1 wt.%. The mechanically activated carbon-doped titanium powder mixtures, as well as the mechanically activated titanium powder subjected to HC (temperature of 900°C and holding time of 15 min) and additional annealing at different temperatures and holding times are studied by optical metallography, scanning electron microscopy, and X-ray diffraction and chemical analysis. According to the metallography and X-ray diffraction results, the TiC content in the HC composite has been found to be significantly higher than the estimated value. The reason is a destruction of ethanol molecules during mechanical activation resulting in the release of carbon and hydrogen. To obtain the targeted (no more than 10 vol.%) TiC content in the titanium matrix composite, it is necessary to establish a specific technological mode for the mechanical activation of the titanium powder.

The products of the combustion synthesis in titanium, silicon, and aluminum powder mixtures under a wave combustion mode are studied using X-ray diffraction analysis and optical metallography. The synthesis products contain titanium silicide Ti5Si3 and titanium aluminide TiAl3, the ratio of which depends on the content of aluminum powder in the reaction mixtures. The combustion temperature of the mixtures decreases with an increase in the aluminum content owing to the substitution of titanium aluminide in the synthesis products for titanium silicide, which has a multiply less negative enthalpy of formation compared to that of the silicide. The effect of the combustion temperature on the dispersity of the structure of the synthesis products is considered using the concepts of the features of the growth of silicide and aluminide nuclei in a liquid metal solution.

\"Titanium carbide - a high speed steel (HSS) steel binder\" metal matrix composites were synthesized by the wave combustion mode and investigated. Composite powders \"TiC + HSS\" obtained by crashing of the self-propagating high temperature synthesis (SHS) cakes were used for electron-beam surfacing of the coatings. An microstructure evolution of composite powder granules during of the surfacing is traced. The evolution involves a partial dissolution of the composite granules in the melt of the surfacing bath and subsequent crystallization of dispersed carbide particles in the dendrites form from a liquid metal solution containing titanium and carbon. The microstructure of the deposited coatings correlates with their hardness and abrasive wear resistance. The abrasive wear mechanism of the coatings is discussed.

Phase composition and structure of \"TiC-NiCrBSi alloy binder\" metal matrix composite powders have been investigated. The composites were synthesized from titanium, black carbon and Ni77Cr15Si3B2 alloy reaction powder mixtures by self-propagating high temperature synthesis (SHS). The composite powders were produced by crushing of SHS cakes. A size of TiC inclusions in NiCrSiB matrix depends on the content of NiCrBSi in the reactive powder mixtures and varies from 7.3 to 1.2 μm.

Using the method of hot compaction (HC) of mechanically activated powder mixtures of titanium and carbon (carbon black) in an ethanol medium, titanium-matrix composites with a carbide strengthening phase were obtained. To obtain a composite with different content of titanium carbide, the amount of carbon was varied within the range of 0-1 wt.%. The mechanically activated carbon-doped titanium powder mixtures, as well as the mechanically activated titanium powder subjected to HC (temperature of 900[degrees]C and holding time of 15 min) and additional annealing at different temperatures and holding times are studied by optical metallography, scanning electron microscopy, and X-ray diffraction and chemical analysis. According to the metallography and X-ray diffraction results, the TiC content in the HC composite has been found to be significantly higher than the estimated value. The reason is a destruction of ethanol molecules during mechanical activation resulting in the release of carbon and hydrogen. To obtain the targeted (no more than 10 vol.%) TiC content in the titanium matrix composite, it is necessary to establish a specific technological mode for the mechanical activation of the titanium powder. Keywords: titanium, titanium carbide, ethanol, structure, phase composition, elemental composition, titanium matrix composites.

The paper presents the results of the X-ray diffraction analysis, scanning electron microscopy, and electron probe micro-analysis of the products synthesized from the titanium, carbon (soot), and aluminum powder compositions in the wave combustion mode. It is found that the carbon/aluminum ratio in the reactive powder compositions has an effect on the combustion temperature, phase composition, and structure of the synthesis products. The major phase in the synthesis products is titanium carbide with the particle size monotonically decreasing in the composite structure with decreasing carbon/aluminum ratio in the reactive powder compositions resulting from the reduction in the combustion temperature. Based on the structural investigations of the synthesized composites, their practical application as feedstocks is discussed in relation to the coating deposition and cladding, and as bulk materials consolidated via hot isostatic pressing or spark plasma sintering.

AlTiN nitride coatings on the surfaces of metal-working tools can greatly extend their service life. The coatings are deposited from plasma flows generated by vacuum arc burning on the cathode surface. The elemental and charge composition of the plasma flows, as well as the content of metal drops, depend on the cathode’s structure. In this paper, the microstructure, elemental, and phase compositions of the surface layer of Al-Ti cathodes subjected to vacuum arc heating were studied. These cathodes had similar elemental compositions (Ti + 50 at.% Al) but differed from one another in their phase composition and microstructure (grain size, porosity). The cathodes were studied by X-ray diffraction analysis, scanning electron microscopy, and electron probe analysis. It was found that during vacuum arc heating, surface fusion or thermal cracking of the cathode’s surface layer occurs. The thickness, structure, and phase composition of the modified layer were controlled by the thermal conductivity of the cathode material, which, in turn, depended on the phase composition and porosity of the cathodes. The maximum thickness of the modified layer (up to 400 µm) was observed on the surface of the sintered cathode due to the lower thermal conductivity of the porous structure of the cathode. The obtained results can be used for the development of coating deposition technology based on vacuum arc sputtering of multicomponent cathodes.