In-situ reinforced MoSi 2 composites by mechanical alloying

Abstract

Intermetallics have been the focus of recent interest in the development of high temperature structural materials. This paper reports that MoSi{sub 2} is one of the promising candidate materials for such applications due to its excellent oxidation resistance, low density, and high electrical and thermal conductivity. However, it is plagued by low room temperature fracture toughness and elevated temperature strength, in addition to intermediate temperature pesting behavior. While powder processing appears to be the preferred route to the fabrication of MoSi{sub 2}, it results in the incorporation of substantial amounts of an amorphous silica phase upon consolidation. The presence of these amorphous silica particles is thought to be detrimental to the mechanical properties, as they can serve as potential crack nucleation sites that ultimately degrade the room temperature strength and toughness. The elevated temperature properties are also degraded by the silica due to its softening characteristics at temperatures above 1473K. It has also been shown that the presence of both silica and free silicon degrades the protective diffusion barrier coatings on ductile fiber reinforced MoSi{sub 2} composites.