Explore the vast range of titles available.

The structure and phase composition of powder materials of the Ti–Al–B system formed in the process of vacuum sintering and synthesis in the mode of high temperature self-propagating synthesis (SHS) are considered depending on the combination of components in the form of elementary powders (Ti, Al and B) and using the finished titanium diboride (TiB 2 ) compound. The proportions of the components were calculated in such a way that the number of interacting elements was sufficient to form a two-phase TiAl 3 + TiB 2 composition. When sintering the Ti + Al + TiB 2 mixture, the diboride is retained, but the presence of TiB is noted as a result of the redistribution of boron due to its migration into free titanium. It was discovered that sintering of compacts from the mixture based on elemental powders (Ti, Al and B) occurs under conditions of high exothermic effect, as a result of which the samples were destroyed. This made it possible to use this mixture under conditions of high-temperature synthesis in combustion mode. As a result of both vacuum sintering and SHS compacting, aluminide TiAl 3 and titanium diboride (TiB 2 ) are mainly formed from a mixture of elemental powders (Ti, Al and B). In this case, some transition phases can be observed. It is shown that after the synthesis of the Ti + Al + B mixture, it is possible to obtain a powder product from which compacts are well sintered while maintaining their shape with a slight shrinkage.

Theoretical and experimental study of the synthesis of porous composites from powder mixtures for Ti-Si and Ti-Al-Si systems in the reaction sintering mode is carried out in the present work. The thermokinetic model of reaction sintering is formulated taking into account competing physicochemical stages. The model includes the heat balance equation, the kinetic equations for the components involved in the reactions, the kinetic equation for porosity changing during heating, reaction sintering, and cooling. The melting is assumed to occur within the temperature range of liquidity and solidus. These processes lead to the appearance of local stresses and volumetric changes. The results of experimental studies show good agreement with the numerical calculations.

The paper presents the structure and phase composition of Ti−Al−Si powder composites produced in different conditions, which include vacuum sintering and self-propagating high-temperature synthesis (SHS). The certain ratios of reactive components are used in experiments for the formation of two-phase composites, matching the TiAl 3 + Ti 5 Si 3 and Ti 3 Al + Ti 5 Si 3 compositions. The vacuum sintering of Ti−Al−Si powder composites provides mostly the formation of the two-phase structure, but the quantitative ratio of the appeared phases can considerably differ from the calculated compositions. The lattice parameters in these phases are rather distorted. The analysis of the synthesis in the wave mode combustion of Ti−Al−Si powder composites shows that the synthesis completes only in the TiAl 3 + Ti 5 Si 3 composite. This allows us to prepare the powder from the synthesized product. The paper analyzes the behavior of the synthesized powder based on the phase composition of the TiAl 3 + Ti 5 Si 3 composite after the vacuum sintering of the powder compacts. It is found that after the 1300°C vacuum sintering of the SHS products based on the TiAl 3 + Ti 5 Si 3 composite, its qualitative phase composition remains with a small change in the quantitative phase composition. The compaction of the SHS products is observed together with the reduction in the residual porosity.

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.

Volume changes during solid-phase sintering and the structure and phase composition of materials sintered of the binary and ternary powder foundry alloys of the Al-Cr(Si,Ti) system are investigated. The powders for sintering were obtained by self-propagating high-temperature synthesis (SHS) in the mixtures of elementary powders of four target compositions with the subsequent crashing of the cakes and sieving of fine fractions. When sintering all the pressings under study, volume shrinkage, which monotonically increased with an temperature rise and the duration of the isothermal holding, take place. The results of structural investigations of the sintered materials, which were performed applying the methods of X-ray structural analysis, electron probe microanalysis, optical and scanning microscopy, are discussed jointly with the results of investigations of the volume variations during sintering.

Titanium–silicon powder materials produced by vacuum sintering of elementary powder mixtures containing up to 25 at.% Si are examined. The structurization of sintered materials with different compositions is studied. The bulk changes of samples in sintering depending on the content of the second component and sintering temperature are analyzed. The process conditions to produce materials of minimum porosity are determined.

The structure and phase composition of (TiB)–Ti powder metal matrix composites synthesized by wave combustion with subsequent vacuum sintering are studied. The selected ratio of the reacting components correspond to the presence of unreacted titanium in the combustion products. The behavior of the SHS composite powders synthesized by vacuum sintering is estimated. An analysis of the volumetric and structural changes in the synthesized powder compacts demonstrates that at sintering temperatures of 1300–1350°С, no significant structure transformation occurs, and a slight decrease in the compact volume and the residual pore content is observed. A qualitative phase composition is maintained regardless of the amount of excess titanium and the selected temperature of sintering of the metal matrix composite. The vacuum sintering condition facilitates the redistribution of proportions of phases formed in a nonequilibrium state during synthesis. After sintering, the titanium diboride phase content decreases in favor of a more stable titanium monoboride.

The paper presents the result of studies of composite powders produced by self-propagating high temperature synthesis (SHS) in the reaction mixtures of titanium, carbon and high chrome cast iron, and electron-beam coatings based on them. It was found that the morphology and dispersion of titanium carbide particles in the SHS-product were determined by cast iron powder content in the reaction mixtures. The effect of content of the SHS powders on the characteristics of electron-beam coatings, including abrasive wear resistance of facing coatings was shown.

The results of studying of sintered powder Ti-TiC compositions are presented in this paper. Materials varying with carbon content and titanium powder dispersity sintered at 1300°С and were investigated. Sintering duration, carbon content and titanium dispersity were shown to influence on microstructure, average grain size, as well as porosity and crystal lattice parameters of titanium and titanium carbide.

Sintering conditions for the fabrication of high strength, porous, permeable, titanium--porous titanium composites were determined. The structure and strength properties of porous permeable titanium after inward growth of bone tissue for periods of 1, 3, and 6 months were investigated. The minimum time necessary for the growth of bone tissue into an implant was determined.[PUBLICATION ABSTRACT]