scholarly journals Specific features of formation of bulk porous systems in the self-propagating high-temperature synthesis. Borides

2019 ◽  
Vol 64 (1) ◽  
pp. 14-24 ◽  
Author(s):  
V. V. Klubovich ◽  
M. M. Kulak ◽  
B. B. Khina
Keyword(s):  
Phase Composition ◽  
High Temperature ◽  
Structure Formation ◽  
Grain Refinement ◽  
The Self ◽  
Synthesis Process ◽  
Temperature Synthesis ◽  
Thermal Factor ◽  
High Temperature Synthesis ◽  
Initial Charge

The effect of ultrasound oscillations (USO) on the combustion velocity and temperature, phase composition and microstructure of compounds produced by the self-propagating high-temperature synthesis (SHS) in the Ti–B system is studied using the earlier developed experimental setup. It is shown that the effect of powerful ultrasound on SHS is connected with the thermal factor, viz. the enhancement of heat removal from the specimen surface due to forced convection, and the physical (non-thermal) factor that consists in the influence of USO on the melt spreading and crystallization of different phases in the SHS wave. It is demonstrated that for multiphase system Ti–B an increase of the boron content in the initial charge leads to grain refinement of the synthesized product and the imposition of USO on the SHS results in a change in the grain morphology: their shape becomes closer to equiaxial. In composition Ti+1.5B, under the action of USO cubic-shape product grains are observed on the inner surface of pores, and in composition Ti+2.0B the synthesized TiB2 grains become more vividly facetted.As a result of imposition of ultrasound on the synthesis process, grain refinement is observed for all the compositions along with the formation of a large number of borides and their redistribution in the volume. The use of ultrasound brings about changes in the quantitative phase composition of the synthesis products and the ratio between the orthorhombic and cubic modifications of phase TiB. The research has shown that the presence of pores in the initial charge plays an important role in the structure formation of the final product, and hence it appears impossible to obtain an equilibrium material by the SHS method. It is found that an optimal USO amplitude exists at which it is possible to obtain uniform fine-grained structure of the material. This permits controlling the structure formation at SHS. 

scholarly journals Effect of powerful ultrasound on the combustion processes and phase composition of refractory compounds of titanium at the self-propagating high-temperature synthesis

2019 ◽  
Vol 62 (6) ◽  
pp. 674-684
Author(s):  
V. V. Klubovich ◽  
M. M. Kulak ◽  
B. B. Khina
Keyword(s):  
Heat Transfer ◽  
Phase Composition ◽  
High Temperature ◽  
The Self ◽  
Temperature Synthesis ◽  
Ultrasound Frequency ◽  
Refractory Compounds ◽  
High Temperature Synthesis ◽  
Combustion Processes ◽  
Heterogeneous Interactions

The effect of ultrasound oscillations (USO) on the heat transfer conditions between a specimen and environment is examined using a specially developed experimental facility. The influence of the USO amplitude on the combustion temperature and velocity as well as on the phase composition and crystal lattice parameters of the synthesized compounds is studied for the self-propagating high-temperature synthesis (SHS) in Ti–С(Si,B) systems. The heat transfer coefficient on the surface of a specimen during its oscillations with an ultrasound frequency is assessed. Possible mechanisms of the effect of USO on the SHS process are considered. It is demonstrated that a decrease in the SHS temperature is connected with cooling the specimen due to forced convection of a surrounding gas, while a change in a phase composition of the synthesized material and the crystallographic parameters of the phases occurs due to changes in the conditions of high-temperature heterogeneous interactions in the SHS wave.

Self-Propagating High-Temperature Synthesis of Dense TiC-TiB2-MeO Ceramics

2006 ◽  
Vol 45 ◽  
pp. 1018-1023
Author(s):  
Vladimir A. Shcherbakov ◽  
Anton V. Phitev ◽  
N.V. Sachkova ◽  
Fabio A. Deorsola ◽  
Dario Vallauri ◽  
...  
Keyword(s):  
High Temperature ◽  
Liquid Phase ◽  
Metal Oxides ◽  
Structure Formation ◽  
Grain Refinement ◽  
Mechanical Characterization ◽  
Ceramic Materials ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Full Densification

The aim of this work is the preparation and study of the mechanisms of structure formation of dense ceramics based on the TiC–TiB2–MeO system obtained by pressure–assisted Self-propagating High-temperature Synthesis. SHS systems were selected on the basis of thermodynamic analysis as suitable to realise regimes of synthesis with formation of liquid phase allowing a full densification. It was observed that at the adiabatic temperature the liquid phase formed in the SHS products consists of either melted oxides or eutectic TiC–TiB2. The results of microstructural observations and mechanical characterization confirm that the metal oxides effectively promote the densification of the final products and the grain refinement of the SHSproduced ceramic materials.

scholarly journals High-Temperature Synthesis of Metal–Matrix Composites (Ni-Ti)-TiB2

2021 ◽  
Vol 11 (5) ◽  
pp. 2426
Author(s):  
Vladimir Promakhov ◽  
Alexey Matveev ◽  
Nikita Schulz ◽  
Mikhail Grigoriev ◽  
Andrey Olisov ◽  
...  
Keyword(s):  
High Temperature ◽  
Composite Materials ◽  
Metal Matrix Composite ◽  
Matrix Composite ◽  
Metal Matrix ◽  
Average Particle Size ◽  
Synthesis Process ◽  
Average Particle ◽  
Temperature Synthesis ◽  
High Temperature Synthesis

Currently, metal–matrix composite materials are some of the most promising types of materials, and they combine the advantages of a metal matrix and reinforcing particles/fibres. Within the framework of this article, the high-temperature synthesis of metal–matrix composite materials based on the (Ni-Ti)-TiB2 system was studied. The selected approaches make it possible to obtain composite materials of various compositions without contamination and with a high degree of energy efficiency during production processes. Combustion processes in the samples of a 63.5 wt.% NiB + 36.5 wt.% Ti mixture and the phase composition and structure of the synthesis products were researched. It has been established that the synthesis process in the samples proceeds via the spin combustion mechanism. It has been shown that self-propagating high-temperature synthesis (SHS) powder particles have a composite structure and consist of a Ni-Ti matrix and TiB2 reinforcement inclusions that are uniformly distributed inside it. The inclusion size lies in the range between 0.1 and 4 µm, and the average particle size is 0.57 µm. The obtained metal-matrix composite materials can be used in additive manufacturing technologies as ligatures for heat-resistant alloys, as well as for the synthesis of composites using traditional methods of powder metallurgy.

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