The mechanism of phase and structure formation of the Ti-B-Fe system in a combustion wave

Abstract

The mechanism of phase changes in the Ti-B-Fe system in a combustion wave for a mixture of Ti, B, and Fe powders and a ferroboron alloy-titanium mixture with the same proportion of elements is studied. It is found that the mechanism of structure formation depends significantly on the type of contact between the initial components. An x-ray phase and x-ray spectrum and structural microanalyses of the quenched layers of specimens show that the first contact melts occurring in the combustion wave are ferroboron (the first type of mixture) or ferrotitanium (the second type) melts. In the first case, the calculated high-melting compound TiB2 forms as a result of the interaction between the two melts; in the second case, it forms as a result of the interaction of the melt with solid ferroboron, which, in turn, determines the different type of microstructure of the final combustion products. The highly disperse and more homogeneous structure of the products forms after combustion of the second-type mixture. A method of producing the Ti-B-Fe pore-free composite produced during the self-propagating high-temperature synthesis (SHS-composite) by combining the combustion with rolling of the synthesis products is considered. In properties, theresulting material is similar to tungsten-carbide materials.