A. E. Sytschev

Hot forging of MAX compounds SHS-produced in the Ti-Al-C system

Investigated was the forgeability (extent of compression) of still hot SHS products (MAX phases) formed in the Ti-Al-C system at relatively low applied pressures (1.5–15.0 MPa in a press punch) in conditions of free SHS compression. The extent of compression was measured as a function of time delay (between the end of reaction and compression) and applied pressure. Characterized were the microstructure and phase composition of thus obtained MAX compounds.

SHS joining in the Ti-Si-C system: Structure of transition layer

Explored was SHS joining in sandwiches of (Ti + yC)/(Ti + xSi) powder compacts, and the transition layers were characterized by SEM, EDS, XRD, and optical microscopy. The transition layers were found to contain titanium carbides, titanium silicides, and Ti3SiC2. The results suggest that, in the systems under study, the weld seam is formed due to convective interpenetration of melted combustion products.

Simultaneous synthesis and joining of a Ni-Al-Based layer to a Mo foil by SHS

Explored was the simultaneous synthesis and joining of a Ni-Al-based layer to a Mo foil by SHS in Al-Ni and Al-NiO mixtures. It has been demonstrated that variation in reaction conditions can be used as a tool for regulating a thickness of a deposited coating and its phase composition. Under some certain conditions, a Mo foil can be fully consumed in the reaction with combustion products to yield a product of desired composition.

Synthesis of Ti-Al-based materials by thermal explosion

Ti-Al-based materials reinforced with TiC and TiB2 particles were prepared by thermal explosion in compacted (Ti + 0.3B4C) + xAl and (Ti + 3Al) + yB4C blends. The structure/properties of synthesized materials were characterized by XRD, SEM, and mechanical testing. An increase in x was found to affect the microstructure of products (lower grain size) and to have no influence on reaction temperature. An increase in y was found to decrease reaction temperature and to change the structure/composition of products toward better viscoelastic behavior.

Deposition of composite metallic coating onto Al through mechanical impregnation followed by thermal treatment

Investigated were the processes taking place in thermally treated Al plates mechanically impregnated with a mixture of metallic particles. Vibratory treatment of an Al surface in a powder mixture of metals was found to result in destruction of the surface Al2O3 film and formation of extensive physical contacts between the Al matrix and the metallic particles mechanically impregnated into the near-surface layer of Al. Subsequent thermal treatment was then used to launch chemical reaction yielding intermetallides within the impregnated layer. Performing SHS reactions yielding melted intermetallides in the coatings (or pellets) deposited (or placed) onto the surface of thus treated Al plates, one can obtain strong weld joining between solidified SHS products and Al. This approach can also be used for deposition of coatings with a desired composition onto Al substrates.

Interaction of SHS-produced melt with a Ti surface in microgravity conditions

In this paper, we report on the SHS reaction 3NiO + 5Al → 3NiAl + Al2O3 carried out aboard International Space Station (Flight Mission 18) with special emphasis on the effect of the composition of reaction products on the composition of coatings formed on a Ti substrate.

Combustion synthesis of porous Ti-Co alloys for orthopedic applications

A mechanoactivation of Ti-Co mixtures was used to perform the SHS of Ti-Co alloys without preheating and heat-generating additives. The SHS of Ti-Co alloys from non-activated Ti + Co green mixtures containing an admixture of B4C as a heat-generating agent without preliminary heating was carried out for the first time. The phase composition, structure, and mechanical properties of synthesized materials were explored upon variation in [B4C] within the range 2–10 wt %. The desired structure/properties of combustion products were attained at [B4C] = 2–4 wt %. The materials synthesized under the above optimal conditions exhibited a developed and uniformly distributed system of pores (largely open) with a size of 150–400 μm, at a wall thickness of 70–100 μm. By their properties (interconnected pores in the range 200–500 μm, compression strength 40–65 MPa), the synthesized materials can be recommended for use as metallic scaffolds intended for bone tissue ingrowths.

Influence of gravity on self-propagating high-temperature thermite reactions: The case of Cu2O-Al and Cu2O-Cu-Al systems

The effect of gravity on self-propagating reactions is investigated for the case of the thermite systems Cu2O-Al and Cu2O-Cu-Al. It is found that the gravitational overload influences wave velocity, degree of expulsion, sample shrinkage as well as product microstructure. The mechanism of structure formation under different gravity levels is also examined and the corresponding transformation zones are identified.

SHS of MAX compounds in the Ti-Si-C system: Influence of mechanical activation

Mechanical activation of Ti-Si-C green mixtures was found to negatively affect the composition, microstructure, and properties of synthesized Ti3SiC2.

Formation of nanolaminate structures in the Ti-Si-C system: A crystallochemical study

Combustion synthesis of laminate Ti3SiC2 structures from the elements was explored by time-resolved XRD. Crystallochemical modeling and quantum-chemical calculations suggest that the laminate structure of Ti3SiC2 arises due to regular accumulation of difference between the bond lengths of Ti3SiC2 and TiC and population of thus formed vacancies with Si atoms in the TiC lattice.