Processing and properties of MoSi2–SiC and MoSi2–Al2O3

Molybdenum disilicide (MoSi2) is a candidate material for high temperature structural applications due to its high melting point and excellent oxidation resistance. A major impediment to implementing this material is its low temperature fracture toughness. Earlier studies examined polycrystalline MoSi2 for the role of grain size and SiO2 impurity distribution on the fracture response via indentation. The goal of this study is to apply this indentation analysis to MoSi2 containing additions of either Al2O3 or SiC. These additions modify the microstructure and result in changes to the indentation cracking behavior. Indentation crack responses and crack lengths are recorded and the fracture toughness values are determined. An explanation is presented for the formation of a tortuous crack path that increases the fracture toughness for the sample with the SiC addition.