Effect of Chromium Content on Formation of (Mo1-x-Crx) Si2 Nanocomposite Powders via Mechanical Alloying

(Mo1-x-Crx)Si2 composite powders were successfully synthesized by ball milling of Mo, Cr and Si elemental powders. Effects of the Cr content, milling time and annealing temperature were investigated. X-ray diffraction (XRD) was used to characterize the milled and annealed powders. The morphological and microstructural evolutions were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results showed that this composite formed after 20 h of milling. Increasing Cr content from 0.1 to 0.25 or 0.4 at.% changed the polymorph of synthesized MoSi2 from to as well as the formation reaction mechanism from mechanically induced self sustaining reaction (MSR) to gradual. Annealing of the milled powders led to the formation of  -MoSi2 in all Cr contents. An average grain size of less than 40 nm was obtained for all Cr contents at the end of milling. In spite of grain growth and strain release during annealing, these nanocomposites remained in their nanocrystalline nature.