MoSi2–ZrO2 composites—fabrication, microstructures and properties

In this study, dense monolithic MoSi2 and MoSi2–ZrO2 composites were fabricated by hot-pressing from mechanically alloyed (MA) and commercial MoSi2 powders, unstabilized zirconia (UZ) and yttria partially stabilized zirconia (YPSZ) powders. The microstructures and properties of these materials were characterized. Hot-pressed monolithic materials and composites were consolidated to 96.1–99.5% density. Zirconia phases identified in the composites MoSi2–UZ and MoSi2–YPSZ were monoclinic and tetragonal, respectively. The MA–MoSi2 powder prepared materials have a higher hardness due to the refinement of the matrix. The toughness of the composites UZ and YPSZ were 2.4 times and 20% higher than that of MoSi2. The predominating fracture modes have been identified. High density of microcracks and dislocations were observed in UZ composites but not in YPSZ composites. Microcracking is suggested to be the main toughening mechanism for the former; while for the latter, the improvement in toughness could be attributed, at least partly, to crack deflection.