Ductile Phase Toughening of MoSi2: Effect of Reinforcement Morphology

The effects of ductile reinforcement morphology on the mechanical behavior of MoSi2 reinforced with 20 vol.% Nb are presented. While all the composites exhibit improved fracture toughness relative to the monolithic MoSi2, the most significant improvement is obtained in the composite with laminate reinforcement, followed by coarse fiber, fine fiber and particulate reinforcements. Bend strength measurements indicate a ductile-brittle-transition-temperature of ∼1250°C, and highlight the attractive properties of laminate reinforced composite. Preliminary studies of room temperature fatigue crack growth in particulate reinforced composites show a stable fatigue crack growth, which is not achieved in monolithic MoSi2. Possible ways of achieving a better combination of mechanical properties are also discussed.