Self-propagating High-temperature Synthesis Products Research Articles

Self-propagating high temperature synthesis (SHS) of ZrC-TiC nanocomposites: Comparison of Mg and Al reductant usage and process optimization

This study investigated the production of ZrC-TiC composite nanopowders by SHS process in TiO2-ZrO2-C-Mg/Al systems. Mg and Al charge stoichiometries and composite charge stoichiometries were optimized for SHS processes. The most precise procedural stages were identified for refining the SHS product; acid concentrations were optimized for Mg usage and an innovative chemical method was developed to eliminate and/or decrease the amount of Al2O3 by-product, enabling the utilization of Al. Thermochemical simulations were conducted for thermodynamic evaluations (adiabatic temperature and specific heat) and characterizations were performed by XRD and SEM-EDS analysis. The findings indicated that utilizing both reductants allowed for the synthesis of ZrC-TiC-(Al2O3) particles that have considerable surface area and commercial purity. The outcomes demonstrated that Magnesium is a more effective reductant, yet Aluminium, also serves as a viable reductant, even though leading to an increase in process steps, but enabling in-situ formation of sinterability and toughness enhancing Al2O3. A novel chemical route including pre-acid leaching, NaOH fusion, water leaching, HCl leaching was identified for the synthesis of ZrC-TiC-Al2O3 composite powder where the amount of Al2O3 could be organized (according to the desired mechanical properties) by optimization.

Determination of nitrogen in titanium, aluminum, silicon, hafnium nitrides and compositions on their base using a Metavak-AK analyzer

Methods for determining nitrogen in the products of self-propagating high-temperature synthesis (SHS), i.e., titanium, aluminum, silicon, and hafnium nitrides using a Metavak-AK gas analyzer have been developed. The optimal modes of analysis have been selected: the time and temperature of degassing of the crucible with flux in the furnace, the time and temperature of purging the extraction chamber with the sample, the time of automatic dumping of the sample from the loading chamber into the crucible, the time and temperature of purging the chamber after loading, the time of removal of gaseous products of reduction melting and registration of nitrogen signals. Furnace operating programs were compiled to determine the nitrogen content in TiN, AlN, Si3N4, HfN. Reduction melting of the samples took place in a helium flow at a furnace temperature of 2700°C for TiN, AlN, HfN, and 2500°C for Si3N4. To speed up the process and complete nitrogen extraction, a metal bath was used: nickel grit in the case of titanium and hafnium nitrides, and combined Sn/Ni flux for aluminum and silicon nitrides. The nitrogen content in the studied samples was determined in the range from 0.12 up to 39.3 %wt., the relative standard deviation was 0.6 – 3.6%. The accuracy of the results obtained on a Metavak-AK gas analyzer is confirmed by the Kjeldahl and Dumas reference methods.

Influence of partial titanium substitution by its hydride on structure and mechanical properties of TNM-B1 heat-resistant alloy, obtained by SHS powder hot isostatic pressing

This paper investigates the influence of partial substitution of titanium by its hydride on the microstructure and mechanical properties of TNM-B1 alloy obtained by powder metallurgy technology. The impact of the Ti:TiH2 ratio in the reaction mixture and heat treatment modes on the microstructure and mechanical properties of TNM-B1+1%Y2O3 alloy, obtained using high-energy ball milling (HEBM), selfpropagating high-temperature synthesis (SHS), and hot isostatic pressing (HIP) methods, has been examined. It was observed that a 10 % substitution of titanium with its hydride in the reaction mixtures reduces the oxygen content in SHS products from 1 % to 0.8 % due to the generation of a reducing atmosphere during the decomposition of TiH2 in the combustion wave. When the Ti : TiH2 ratio is 90 : 10, highest mechanical properties of TNM-B1+1%Y2O3 alloy were achieved: a compressive strength (σu) of 1200±15 MPa and a yield strength (YS) of 1030±25 MPa. An increase in the proportion of TiH2 results in a higher content of oxygen impurity, leading to the formation of Al2O3, which reduces the strength and ductility of the material. With additional heat treatment of TNM-B1+1%Y2O3 alloy, the globular structure transforms into a partially lamellar one, leading to an increase in σu by 50–300 MPa, depending on the TiH2 content. This attributed to a decrease in the average grain size and a reduction in dislocation mobility during deformation.

Structure and phase composition of SHS composites based on Al–Ti–B system with different Al content

The paper deals with the influence of the Al content in the initial Al–Ti–B system on self-propagating high-temperature synthesis (SHS) processes, structure, and phase composition of synthesized products. It is found that the higher Al content leads to a temperature decrease of exothermic reaction and changes its wavefront propagation from layerwise to spinwise multiple locations. SHS products obtained from the Al–Ti–B system contain titanium diboride (TiB2) and aluminum (Al) phases. The weight content of phases in SHS products depends on the Al content in the initial powder mix and approximately matches the weight content of its components. The higher Al content provides a decrease in the size of the coherent scattering region for detected phases. SHS products obtained from the Al–Ti–B system with 10 wt% Al, consist of separate TiB2 particles coated with aluminum film. The Al content increased up to 30 and 60 wt%, provides the formation of the metal matrix structure. In this case, synthesis products consist of the aluminum matrix with TiB2 particles distributed inside. It is found that the growth in the Al content from 10 to 60 wt% in the initial Al–Ti–B system, results in the size reduction of TiB2 particles in SHS products from 3.37 to 0.41 μm, respectively.

Mechanical activation time of 6B2O3–13Al powder mixture vs. structure and phase composition of SHS products

The paper discusses the time of mechanical activation of the 6B2O3–13Al powder mixture affecting the self-propagating high-temperature synthesis (SHS), exothermic reaction temperature, structure, and phase composition of synthesis products. It is found that the time increase of the mechanical activation up to 180 min leads to a reduction in the average size of aluminum and boron trioxide particles down to 4.8 and 3.5 μm, respectively. Aluminum particles with boron trioxide inclusions are observed on the particle surface and inside their structure. Changes in the particle size and structure in the initial mixture components modify the SHS reaction front from chaotic to by layers. The structure of SHS products consists of the alumina layer (63–68 wt%) with aluminum dodecaboride (AlB12) particles (32–37 wt%) distributed under this layer. After 10 and 60 min of mechanical activation, acicular and elongated AlB12 particles appear in products synthesized from the 6B2O3–13Al powder mixture. Based on the data obtained, the SHS with subsequent mechanical activation is proposed for the fabrication of the Al2O3/AlB12 nanocomposite from the 6B2O3–13Al powder mixture. It is shown that after washing grinded SHS products with hydrochloric acid solution, the synthesized powder contains 100 wt% AlB12.

Reaction Behavior and Formation Mechanism of ZrB2 and ZrC from the Ni-Zr-B4C System during Self-Propagating High-Temperature Synthesis

Self-propagating high-temperature synthesis (SHS) is a good way to prepare ZrB2-ZrC/metal cermet composites. In this work, ZrB2-ZrC/Ni cermet composites with various Ni contents were successfully fabricated by SHS using the Ni-Zr-B4C system. The effects of Ni content and particle size of the B4C powder on the SHS reaction were investigated. The results indicated that with an increase in Ni content, the adiabatic temperature, maximum combustion temperature, ignition delay time, and ceramic particle size in the product all showed a gradually decreasing trend. The SHS products and the ignition of the SHS reactions were significantly dependent on the B4C particle size. The formation mechanism of ZrB2 and ZrC during SHS from the Ni-Zr-B4C system was proposed based on the combustion wave quenching experiment.

Structural formation of Ti – Al – B composite as a function of the method used to obtain and introduce Boron

This paper looks at the possibility of obtaining ternary borides with a nanolaminate structure (of the MAX phase type) in the Ti – Al – B system by self-propagating high-temperature synthesis (SHS). Different methods were used for introducing boron and titanium. Thus, they were introduced in the form of powders of elemental boron and titanium and in the form of compounds of TiH2 and AlMgB14 (“hydride technology”). Titanium hydride was obtained by annealing the powder at 450 оС in a continuous hydrogen flow. The obtained titanium hydride was mixed with aluminum powder and pressed at a pressure of 6.63·106 Pa. Workpieces with a diameter of 2 cm and a thickness of 0.2 cm were produced, which were then annealed under a programmable temperature regime at 620 оС (below the aluminium melting temperature). The second type of workpieces was obtained by combining titanium hydride with aluminum powder and B/AlMgB14. This mixture was then pressed at a pressure of 6.63·106 Pa. The resulting workpieces (with a diameter of 2 cm and a thickness of 0.2 cm) were annealed at 1.000 оС. The high-boron compound of AlMgB14 was obtained by SHS. The use of the hydride technology leads to the formation of new phases: borides and titanium aluminides. Ternary borides (Ti2AlB) were not found. The authors use the results of a microstructural study and an X-ray energydispersive analysis of the samples, as well as element distribution maps, to demonstrate the possibility of obtaining ternary laminate compounds (of the MAX phase type) in the Ti – Al – B system by SHS using elemental powders. The SHS products are not a homogeneous ternary phase. Ternary laminate borides are located in the Ti3Al intermetallide matrix. All the synthesis techniques used in this research lead to the formation of multiphase products.The work was carried out within the framework of the State assignment of the Tomsk Scientific Center of Siberian branch of RAS, project No. 121031800 148-5 (synthesis of samples via SHS method).The work was carried out under financial support of the Ministry of Education and Science of Russian Federation within the framework of the State assignment No. FSWM-2020-0028.Investigations of microstructure via SEM method were conducted using the equipment of the Tomsk regional common use center of the National Research Tomsk State University (the grant of the Ministry of Education and Science of Russian Federation No. 075-15-2021-693 (No. 13.ЦКП.21.0012)).

Preparation of low-oxygen Ti powder from TiO2 through combining self-propagating high temperature synthesis and electrodeoxidation

An effective method was reported to prepare low-oxygen Ti powder, which included two experimental steps: the fast conversion of TiO2 to TiOx<1 powder by self-propagating high-temperature synthesis (SHS) process and the generation of low-oxygen Ti powder by electrodeoxidizing TiOx<1 powder at the cathode in molten CaCl2. The key intermediate steps were analyzed by XRD, SEM and electrochemical testing techniques. The results demonstrated that TiOx<1 powder (TiO0.325 and TiO0.97) was generated after acid leaching MgO in SHS products with TiO2/Mg molar ratio of 1:2, and the TiOx<1 powder with 16.3 wt.% oxygen could be transformed into pure titanium powder with 0.121 wt.% oxygen by electrodeoxidation at a constant potential of -3.3 V for 10 h. The electrodeoxidation of TiOx<1 powder in CaCl2 molten salt follows the step-by-step deoxidation mode, and the lattice of TiOx<1 powder after electrodeoxidation shrinks.

Improved mechanical properties of porous nitinol by aluminum alloying

Aluminum alloying effects (up to 2 at %) on the macrostructure, microstructure, and mechanical properties of porous nitinol (NiTi) obtained by self-propagating high-temperature synthesis (SHS) were studied. It has been established that Ni and Ti interactions with liquid Al (0.5–1 at % Al) in the SHS process significantly change macrostructure, decrease the size of the interpore bridges, and increase their number, resulting in a larger effective cross-sectional area. An increase in the aluminum content above 1 at % leads to larger interpore bridges in the SHS product. The microhardness of TiNi(Al) increases from 305 HV 50 g to 422 HV 50 g with aluminum concentration, while the fraction of the TiNi(Al) (B2 + B19′) phases decreases from 75% to 50%. The Ti 2 Ni(Al) phase fraction increases from 25% to 50% with Al concentration. The 64 MPa tensile strength and 2.9% fracture strain of porous Ti 50 Ni 49 Al 1 alloy are higher than without Al. The increase in strength is due to the formation of a more homogeneous macrostructure and solid solution strengthening of the alloy-forming phases. Porous NiTi with 0–2 at % Al was obtained by self-propagating high-temperature synthesisNiTiAl macro and microstructure are optimal at 1 at %Al, along with mechanical properties. • Porous NiTi with 0–2 % Al was obtained by self-propagating high-temperature synthesis. • Al doping changed macrostructure and decreased interpore bridge size. • The TiNi(Al) phases fraction decreased from 75 % to 50 % with more Al. • Vickers hardness increased with Al concentration. • The optimal Al content is 0.5–1 % for improved structure and mechanical properties.

Effects of reactants proportions on features of in-situ magnesiothermic self-propagating high temperature synthesized boron carbide powder

The effects of reactant proportions were investigated on features (phase composition, micromorphology and crystal development) of B4C (boron carbide) powder synthesized by in-situ magnesiothermic SHS (self-propagating high temperature synthesis) method, which was based on the perspective of thermodynamic design. The results showed that the reactant proportions were the fundamental reasons affecting the phase composition of the products during the reaction process. Mg addition could decrease the Mg3B2O6/MgO mass ratio of the SHS products. Moreover, C addition would increase the C/B mass ratio of the leached products. When the C molar ratio was 0.2, free boron appeared in the leached products, and the composition of boron carbide was B13C2. When the C molar ratio ≥0.6, the composition of boron carbide changed into B4C, while free carbon began to appear. The lattice parameters a and c of boron carbide crystal dropped with the increase of the C/B mass ratio from 0.1 to 0.3. Meanwhile, carbon atoms gradually entered the boron carbide unit cell. When the C/B mass ratio exceeds 0.3, the lattice parameters tended to be constants of a = 5.608 Å, c = 12.039 Å, while free carbon began to appear in the leached products.

Production of Ferroboron from Wastes by SHS-metallurgy and influence of Ligatures on the Structure/Properties of Cast Iron

Waste, generated during the industrial process negatively affects the environment, but at the same time it is a valuable raw material and can be used to produce new marketable products. The study of the effectiveness of Self-propagating High temperature Synthesis (SHS) methods, which are characterized by the simplicity of the necessary equipment, the purity of the final product and the high processing speed, is under the wide scientific and practical interest to solve the set problem. The work describes technological aspects of production of ferro boron by the method of SHS - metallurgy from iron-containing wastes of rolled production for alloying of cast iron and results of effect of alloying element on degree of boron assimilation with liquid cast iron. Features of Fe-B system combustion have been investigated and the main parameters to control the phase composition of synthesis products have been experimentally established. Effect of overloads on patterns of cast ligatures formation and mechanisms of structure formation of SHS products was studied. It has been shown that an increase in the content of hematite Fe2O3 in iron-containing waste leads to an increase in the content of phase FeB and accordingly, the amount of boron in the ligature. Boron content in ligature is within 3-14%, and phase composition of obtained ligatures consists of Fe2B and FeB phases. Depending on the initial composition of the wastes, the yield of the end product reaches 91 - 94%, and the extraction of boron is 70 - 88%. Combustion processes of high exothermic mixtures allow obtaining a wide range of boron-containing ligatures from industrial wastes. In view of the relatively low melting point of the obtained SHS-ligature, the positive dynamics of boron absorption by liquid iron is established. According to the obtained data, the degree of absorption of the ligature by alloying gray cast iron at 1450 ° C is 80 - 85%. When combined with the treatment of liquid cast iron with magnesium, followed by alloying with the developed ligature, boron losses are reduced by 5-7%. At that uniform distribution of boron micro-additives in volume of treated liquid metal is provided.

On the Structure and Properties of AlMgB14-TiB2 Composites Obtained from SHS Powders by Spark Plasma Sintering.

AlMgB14-TiB2 composite materials were fabricated by self-propagating high-temperature synthesis (SHS) followed by spark plasma sintering of the obtained SHS products. It was found that, during the SHS, the AlMgB14 phase is formed at a donor (Ti + 2B) to acceptor (Al12Mg17-B) mass ratio of 3:7 and 4:6, respectively. The specimen sintered from the SHS powder with the donor:acceptor mass ratio of 5:5 at a temperature of 1470 °C has a uniform skeletal structure. The average hardness of the obtained specimen is 30.1 GPa.

Synthesis of Composite Materials based on TiB2–TiC–Al2O3 and CrB2-Al2O3 in the Combustion Conditions

Borides and carbides attract the attention of developers of heat-resistant and super hard structural materials due to a unique combination of their resistance to high-temperature oxidation, high hardness, wear resistance, electrical and thermal conductivity and etc. The article presents experimental results on obtaining composites based on TiB2-TiC-Al2O3, CrB2-Al2O3 by a method combining self-propagating high-temperature synthesis (SHS) and mechanical activation (MA). The influence of the composition of the initial components, the conditions of SHS and preliminary MA on the formation of the microstructure and phase composition of the SHS-composite based on titanium carbide and titanium, chromium borides has been studied. The SHS products were examined by X-ray diffraction analysis and a scanning electron microscope. High-temperature phases of borides of chromium, titanium, aluminum oxide and their spinel are found in SHS products.

Influence of Ti/C mass ratio on the microstructure of Al-Ti-C master alloy and refinement effect on pure aluminum

Al-Ti-C master alloys with different Ti/C mass ratios were fabricated by self-propagating high-temperature synthesis (SHS).Besides, the effect of Ti/C mass ratio on the microstructure of SHS products and its effect on the grain refinement of industrial pure aluminum were also investigated. The results indicated that the product with Ti/C mass ratio of 4:1 is mainly composed of TiC particles with average size of 0.81 μm, and there is only a small amount of rod-shaped Al3Ti in the sample. When the Ti/C mass ratio is increased to more than 10:1, the rod-shaped Al3Ti is the main product in master alloy, which has the most obvious effect on the refinement of pure aluminum. When the addition amount is 3 wt%, the average grain size decreased to about 191 μm. The Al-Ti-C master alloy with Ti/C mass ratio of 4:1 has better anti refining degradation performance. When add 1.2% of the above master alloy to pure aluminum, holding time 60 min, the macroscopic grains of industrial pure aluminum is more uniform and finer, with an average grain size of 324 µm. The results indicate that the morphology of TiC particles in the product changes from regular sphere to polyhedron with the increases of mass ratio of Ti/C, the average size of TiC particles increases, and the rod-shaped Al3Ti changes from thick rod to thin rod, the average size of rod-shaped Al3Ti decreases.

ВЛИЯНИЕ ЭЛЕМЕНТНОГО ПОРОШКОВОГО СЫРЬЯ НА ФОРМИРОВАНИЕ ПОРИСТОГО КАРКАСА МАХ-ФАЗЫ Ti3AlC2 ПРИ ПОЛУЧЕНИИ МЕТОДОМ СВС

The ternary carbide compound Ti3AlC2 belongs to the so-called MAX-phases – a new type of ceramic materials with unique properties. A simple energy-saving method of self-propagating high-temperature synthesis (SHS) based on combustion is one of the promising methods for the production of this MAX-phase. The application of the SHS technology is to produce a Ti3AlC2 MAX-phase porous frame with the homogeneous porous structure without such defects as large pores, laminations, and cracks is of great interest. The paper investigates the possibility of producing such a porous frame with the maximum content of the Ti3AlC2 MAX-phase using powders of Ti, Al, and C elements of various grades different in particle sizes and carbon forms (soot or graphite) as initial components. Porous frame samples were produced by the open-air burning of pressed briquettes of charge of the initial powders of the selected grades without applying external pressure. The authors studied the macro- and microstructure of the obtained samples, their density, and phase composition. The study shows that using the finest titanium and carbon powders leads to the excessively active combustion with gas evolution and the synthesis of the defective porous samples with the charge briquette shape distortion, large pores, laminations, and cracks. Besides the titanium carbide by-phase, the highest values for the MAX-phase amount in the SHS-product were obtained using the titanium powder of the largest-size fraction together with the graphite powder, rather than soot. The excess aluminum powder addition to the stoichiometric ratio to the initial charge leads to an increase in the MAX-phase amount in the SHS product, compensating for the loss of aluminum due to evaporation. An increase in the sample volume (scale factor) also leads to an increase in the MAX-phase amount in the SHS product due to the slower cooling of the product after the reaction.

Grain Structure Formation in Ni3Al Intermetallic Compound Synthesized Under High-Temperature and Pressure Conditions

The paper presents theoretical and experimental results of studying the grain structure formation of the Ni3Al intermetallic compound produced by self-propagating high-temperature synthesis (SHS) under the pressure and volume exothermic reaction conditions, in a stoichiometric powder mixture. It is shown that the grain size in the SHS-produced intermetallic compound depends on both the preliminary load on the powder mixture and the SHS product deformation during its crystallization. It is found that the increased pressure on the initial powder mixture reduces the grain size in the bulk of the SHS-produced intermetallic compound, whereas its deformation provides a manifold decrease of the grain size at a simultaneous averaging of its distribution in the bulk of the SHS product obtained under pressure.

Composition and Crystalline Structure of Ternary Phases in the Ta–Ni–Al System

The composition and crystal structure of compounds produced by self-propagating high-temperature synthesis (SHS) from the 5Ta–2Ni–3Al (at %) powder mixture followed by vacuum remelting at 3000°C are studied. The SHS product contains the following phases: TaNiAl (Laves τ1 phase), NiAl, Ni2Al3, and Ta. Its microstructure includes Ta85Ni7Al8, Ta52Ni20Al28, and Ta53Ni25Al22 ternary phases according to elemental analysis data. Reflections belonging to no known ternary phases in the Ta–Ni–Al system under consideration are revealed in the X-ray diffraction pattern of the remelted material. Based on the homological approach, it is found that these reflections belong to three phases with the structural types W6Fe7 ( $$R\bar {3}m$$ ), Ti2Ni ( $$Fd\bar {3}m$$ ), and Ta3Al ( $${{P{{4}_{2}}} \mathord{\left/ {\vphantom {{P{{4}_{2}}} {mnm}}} \right. \kern-0em} {mnm}}$$ ). They are identified as reflections of three compounds, Ta6.5Ni6.5, Ti2Ni, and Ta2.84Al0.91, with unit-cell parameters differing from these for the same compounds with the conservation of the structural type. An increase in the unit-cell parameters of all revealed phases is noted when compared with known binary intermetallic compounds. This can be associated with the presence of Al atoms in the crystal lattice from the Ta6.5Ni6.5 phase and Al and Ta atoms in the phase with the Ti2Ni structural type. Phases Ta6.5Ni6.5 and Ti2Ni phases are identified as Ta6Ni6Al and Ta2Ni0.5Al0.5 by X-ray structural analysis and crystal-chemical modeling, and their structural type, composition, and unit-cell parameters are determined. The structure and composition are refined by the full-profile analysis, and the unit-cell parameters of the phases and their quantitative ratio in the material are determined. The phase composition of the material is as follows, wt %: 47 Ta6Ni6Al, 16 Ta2Ni0.5Al0.5, and 37 Ta3Al.

Composition and crystal structure of ternary phases in the Ta-Ni-Al system

The study covers the composition and crystal structure of compounds produced by self-propagating high-temperature synthesis (SHS) from the 5Ta—2Ni—3Al (at.%) powder mixture followed by vacuum remelting at 3000 °C. The SHS product contains the following phases: TaNiAl (Laves τ 1 -phase), NiAl, Ni 2 Al 3 , and Ta. Its microstructure features by the presence ofternary phases with the composi­tion Ta 85 Ni 7 Al 8 , Ta 52 Ni 20 Al 28 and Ta 53 Ni 25 Al 22 according to elemental analysis. The X -ray diffraction pattern of the remelted material revealed reflections that do not belong to any of the known ternary phases in the Ta—Ni—Al system considered. Based on the homological approach, it was found that these reflections belong to three phases with the structural types W 6 Fe 7 ( R 3 m ), Ti 2 Ni ( Fd 3 m ) and Ta3Al (P 4 2 /mnm). It was possible to define them as reflections of three compounds — Ta 6,5 Ni 6,5 , Ti 2 Ni and Ta 2,84 Al 0,91 with unit cell parameters different from those for the same compounds with the retained structural type. The increase in the unit cell parameters for all the phases identified was noted as compared to the known binary intermetallics. It may be associated with the presence of Al atoms in the crystal lattice for the Ta 6.5 Ni 6.5 phase and Al and Ta atoms in the phase with the structural type Ti 2 Ni. X -ray diffraction analysis and crystal-chemical modeling made it possible to identify Ta 6.5 Ni 6.5 and Ti 2 Ni phases as Ta 6 Ni 6 Al and Ta 2 Ni 0.5 Al 0.5 , to determine their structural type, composition and unit cell parameters. Full-profile analysis was conducted to specify the structure and composition and determine unit cell parameters of the phases and their quantitative ratio in the material. The material phase composition is 47 wt.% Ta 6 Ni 6 Al, 16 wt.% Ta 2 Ni 0.5 Al 0.5 and 37 wt.% Ta 3 Al.

Combustion of Titanium-Carbon Black High-Energy Ball-Milled Mixtures in Nitrogen: Formation of Titanium Carbonitrides at Atmospheric Pressure.

In this work, titanium carbonitrides were synthesized by self-propagating high-temperature synthesis (SHS) in nitrogen. For the first time, the synthesis of titanium carbonitrides by combustion was realized in nitrogen at atmospheric pressure. The synthesis was carried out by subjecting high-energy ball-milled titanium–carbon black powder mixtures to combustion in a nitrogen atmosphere. The influence of the ball milling time on the phase composition of the products of SHS conducted in the Ti+0.3C reaction mixture was studied. It was found that the titanium–carbon black mixtures need to be milled for a certain period of time for the combustion synthesis to yield a single-phase carbonitride product.

Structure and Phase Composition of SHS Products in Powder Mixtures of Titanium, Carbon, and Aluminum

TiC + Al binder metal-matrix composites are fabricated by self-propagating high-temperature synthesis (SHS) in reaction power mixtures of titanium, carbon (ash), and aluminum. It is established that stable combustion in a steady wave mode is possible with a content up to 50 wt % aluminum powder in a reaction mixture. Crushing of synthesized loose cakes and subsequent sieve scattering gave composite powders with a cloddy shape close to equilibrium. This shape is favorable for good looseness, which is necessary when using powders for surfacing and sputtering of wear-resistant coatings. Synthesis products are investigated by scanning electron microscopy and X-ray structural (XRS) and energy-dispersive X-ray (EDX) analysis. It is established that the average size of carbide inclusions in the composite structure decreases monotonically with an increase in the content of the aluminum powder inert in the thermal aspect in reaction mixtures. The lattice parameter of titanium carbide determined by the XRS method turned out much smaller than known values for equiatomic-composition carbide. Herewith, no dependence of the lattice parameter on the aluminum content is found for composites. Carbide inclusions in the composite structure are investigated by the EDX method, and it is established that the titanium content corresponds to its concentration in equiatomic-composition carbide. In addition to titanium and carbon, carbide contains up to 2.5 wt % dissolved aluminum, which can affect the carbide lattice parameter.