O. K. Kamynina

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.

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.

High-porosity TiAl foam by volume combustion synthesis

Preparation of high-porous TiAl foam by volume combustion synthesis (VCS) was investigated. It is shown that the optimum conditions for pore formation are attained when gas evolution coincides in time with melting of the reactants.

Multilayer coatings on Ti substrate by SHS method

Explored was the deposition of multilayer TiCx–TixSiy-based coatings onto Ti substrate by SHS method. Sandwich-type green multilayer structures were assembled from Ti foils and Ti + 0.5C, Ti + Si, 5Ti + 3Si, and Ti + 0.65C pellets and ignited under 1 atm of Ar and a load (400 g). Burned sandwiches were characterized by SEM, EDS, and XRD. In all cases, we observed good metal–ceramic joining. Prerequisites for such a joining are (i) the presence of the liquid phase in combustion products, (ii) good metal–ceramic wettability, and (iii) closeness of reaction temperature to the melting point of substrate.

Formation of the structure and phase composition of the Ti–Al–Ta-based materials

The experiments on the fabrication of materials based on the Ti–3Al–0.5Ta and 3Ti–2Al–Ta systems by self-propagating high-temperature synthesis (SHS) are performed. The influence of the composition of the initial mixture, dispersity of powders, and preliminary mechanical activation on the phase composition and structure of the SHS product is investigated. The optimal ratio between the mechanically activated and initial powder in a mixture for the synthesis of materials is determined. The dependence of the structure of final products on the structure of initial powders is established. The use of porous tantalum leads to the formation of the intermetallic matrix based on titanium aluminide with the uniform distribution of Ta particles. It is noteworthy that tantalum powders of both studied series (which differ by dispersity and morphology) partially reacted already at the stage of mechanical activation with the formation of the Al2Ta phase. It is shown that aluminum plays the leading role in processes of mechanical activation in Ti–Al–Ta reaction mixtures. Indeed, a considerable rise of unreacted tantalum particles in the microstructure of sintered samples is observed with a decrease in the amount of aluminum in the reaction mixture.

Low-weight TiAl3 composites by thermal explosion

Dispersion-strengthened TiAl3-based material with uniform structure and high compression strength (σc ≈ 850 MPa) was SHS-produced from Ti–Al–B4C blends in a mode of thermal explosion by using the B4C particles coated with a TiB2/TiC layer as a strengthening agent and preliminary mechanical activation of Ti–Al powder mixtures. The Ti + 3Al mixtures were mechanically activated in a planetary mill for 3 or 6 min and then 10 or 20 wt % of coated B4C particles were added. Pelleted samples were placed into a reaction chamber and heated in an electric furnace under Ar to a self-ignition temperature. The process was optimized and recommended for practical implementation.

SHS in microgravity: Analysis of combustion products formed in the Ti-Al-C system

Characterized was the structure of products and transition layers formed in SHS reactions ignited in multilayered samples in conditions of microgravity.