Effect of ultrasound on combustion synthesis of composite material “TiC–metal binder”

• The effect of ultrasound on the temperature and velocity of CS is studied.
• Changes of the CS-product microstructure under the action of USO are examined.
• The thermal effect of USO on the CS due to forced convection is evaluated.
• The optimal USO amplitude providing uniform fine-grain microstructure is determined.
• The physical reasons for the effect of USO on structure formation are discussed.

An urgent problem in the development of both novel advanced materials obtained by the combustion synthesis (CS) and new CS-based technologies is exploring the ways for affecting the combustion process in situ by an external physical influence. In this work, the effect of ultrasound oscillations (USO) imposed on a burning specimen is studied in the quaternary Ti–C–Ni–Mo system in regard to producing composite material “titanium carbide–metal binder”. An experimental setup is developed and the effect of USO on the CS parameters, viz. the combustion temperature and the CS wave velocity is examined along with the phase composition and microstructure of the synthesized material. It is demonstrated that USO has a twofold effect on the CS: (i) a merely thermal influence connected with forced convection of a surrounding gas, which results in a decrease in the CS temperature and wave velocity, and (ii) a physical, i.e. non-thermal effect, which is ascribed to a change in the nucleation and growth conditions of the refractory product grains (titanium carbide) in the transient melt that exists in the high-temperature zone of the CS wave. The latter can change the microstructure of the target product: with increasing the USO amplitude the grain size distribution of TiC displaces toward smaller sizes. An optimal USO amplitude is found to exist which brings about a sharp maximum on the grain size histogram. Finally, it is shown that imposing USO on the CS process provides a means for modifying the product microstructure and changing the combustion wave characteristics (temperature and velocity).