Reaction Mechanism of Combustion Synthesis of TiAl Intermetallic Compound

Abstract

The reaction mechanism of combustion synthesis of a TiAl intermetallic compound was analyzed by the observation of the reaction process in Ti and Al mixed powder compacts and by a model calculation of the reaction kinetics. A premix of Ti and Al powders was vacuum-heated in an electric furnace to cause self-sustaining reaction. The measurement of the rise in the temperature, the observation of microstructural evolution involved in the reaction process and X-ray phase analysis of the product were performed. It was observed that at the melting point of Al, Al melt surrounded Ti particles and the reaction started and proceeded towards the center of the Ti particle. The synthesis reaction has been analyzed using a spherical shell model which takes into account the microstructural change. The analysis has shown that the reaction is accelerated with reaction time, which is in accordance with the observed self-sustaining reaction. The relative contribution of the diffusion of Al in TiAl and the interface reaction between TiAl and Ti has also been quantified in dependence on the Ti particle size.