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.