Self-propagating exothermic reactions between silicon and transition metals of groups IVA–VIA induced by mechanical alloying

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Chemical reactions between Si and transition metals of groups IVA–VIA induced by mechanical alloying have been investigated. Depending on the exothermicity, reactions could proceed via the solid-state diffusion mechanism or the mechanically induced self-propagating reaction (MSR) mechanism, which is analogous to that of the combustion synthesis. For reactant systems with high adiabatic temperatures (Tad), such as silicides of Zr and Nb, Ti5Si3, TiSi, and MoSi2, spontaneous reactions proceeded via the MSR mechanism. There existed a threshold Tad of 1850 K, below which silicon–metal systems reacted via the gradual solid-state diffusion mechanism during mechanical alloying. Since morphological observations of the MSR product indicated the occurrence of self-propagating reactions in the presence of a liquid phase, the effect of reactant melting temperatures on the threshold Tad was elucidated with additional experiments involving carbon–metal reactant systems.