Formation of Mo−Si−Ti Alloys by Self−propagating Combustion Synthesis

Test specimens with nominal compositions MoSi₂, (Mo_0.9Ti_0.1)Si₂, (Mo_0.8Ti_0.2)Si₂, (Mo_0.7Ti_0.3)Si₂, (Mo_0.6Ti_0.4)Si₂, (Mo_0.5Ti_0.5)Si₂ and (Mo_0.4Ti_0.6)Si₂ were prepared by combustion synthesis. The combustion mode, propagation velocity of combustion wave, combustion temperature and product structure were investigated. Specimens MoSi₂, (Mo_0.9Ti_0.1)Si₂, (Mo_0.8Ti_0.2)Si₂, (Mo_0.7Ti_0.3)Si₂, underwent spontaneously self−propagating combustion synthesis. However, the (Mo_0.6Ti_0.4)Si₂ and (Mo_0.5Ti_0.5)Si₂ specimens required a sustainable energy supply to complete the combustion synthesis reaction. There was no combustion synthesis reaction in specimen (Mo_0.4Ti_0.6)Si₂. The combustion wave propagated along a spiral trajectory from top to the bottom of the specimen compacts in a layer by layer mode. The propagation velocity of the combustion wave reduced with the addition of titanium. The X-ray diffraction analysis showed that the Cll_b-MoSi₂ and C40-(Mo,Ti)Si₂ type phases were formed during combustion synthesis. The intensity of diffraction peaks of C40-(Mo,Ti)Si₂ phase increased with Ti content.

Keywords:
intermetallics; silicide; combustion synthesis; self−propagating high−temperature synthesis; X-ray diffraction