High temperature mechanical behavior of discontinuously reinforced MoSi2 composites

The high temperature flexural properties of MoSi2 and discontinuously reinforced MoSi2 composites have been determined over the range of 1,000 to 1,400 C using four-point bend tests. Tests were performed on in situ processed composites containing 30 volume percent of either SiC, TiB2, or HfB2. These composites were fabricated through a combined XD trademark synthesis and powder processing approach. The yield and flow stresses of the composites were found to be up to 75% greater than those of the unreinforced sample. The apparent ductile-to-brittle transition temperature for the reinforced and unreinforced samples was approximately 1,300 C. This article examines the influence of reinforcement type, morphology, size, and distribution on the high temperature strength and fracture behavior of MoSi2 matrix composites. In addition, the possible influence of matrix grain size and any glassy-phase contaminates are discussed