Evidence for self-sustained MoSi₂ formation during room-temperature high-energy ball milling of elemental powders

We present evidence indicating that rapid, self-sustained, high-temperature reactions play an important role in the formation of tetragonal MoSi₂ during room-temperature high-energy ball milling of elemental powders. Such reactions appear to be ignited by mechanical impact in an intimate, fine-grained, Mo–Si physical mixture formed after an initial milling period. Under certain conditions, limited propagation of self-sustained reactions in these uncompacted powder mixtures renders the compound formation seemingly gradual in bulk-averaged analysis. It is suggested that this type of reaction is an important mechanism in the mechanical alloying of highly exothermic systems. Results are discussed in comparison with similar reactions we observed in ball-milled Al–Ni powders, with self-sustained combustion synthesis previously reported for Mo–Si powders, and with interfacial diffusional reactions in Mo–Si powders or thin-film diffusion couples.