Convective Combustion of a Mechanically Activated Ti + C Mixture under Forced SHS Compaction
Yu. V. Bogatov, V. A. Shcherbakov
Merzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, Russia
Keywords: convective combustion, heterogeneous Ti + C mixture, mechanical activation, SHS compaction, impurity gas
Abstract
The effect of mechanical activation of components and external pressure on the combustion of a heterogeneous Ti + C mixture under SHS compaction conditions has been studied. It is shown that when burning under pressure (15 MPa), a low-speed layered regime (4÷7 cm/s) is realized, without external pressure - non-stationary high-speed combustion modes (50÷70 cm/s): surface-annular and volumetric, carried out due to convective heat and mass transfer. A mechanism for high-speed convective combustion is proposed, based on the ignition of a heterogeneous mixture by a hot impurity gas released in the combustion wave and filtering through layered cracks and other macrodefects in the volume of charge compacts that were formed during the pressing of powder mixtures. Mechanical activation of the components of the reaction mixture reduces the density and strength of the compacts and increases the efficiency of the formation of macrodefects. External pressure has the opposite effect, as it prevents the formation of cracks and the propagation of hot impurity gas through them. Consolidated samples of titanium carbide up to a relative density of 95% were obtained in the bulk combustion mode.
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