Room Temperature Mechanical Behaviour of MoSi₂ Based Laminated Composites

Abstract

Laminated composites have been prepared by stacking powder layers of: (i) MoSi₂-20 vol% SiC composite and MoSi₂-3 wt% Al alloy and (ii) MoSi₂ and MoSi₂-50 vol% BN composite followed by hot-pressing. Microstructural characterization showed well-defined layers, containing structural flaws and having wavy interlayer interfaces. The hardness inside the layers shows variation with distance from the interlayer interface. Cracks formed during fabrication and the indentation-cracking pattern have been analyzed to study the sign and direction of residual stresses. The inherent flaws do not allow for an increase in flexural strength, but the fracture surfaces show mixed-mode crack propagation. The apparent fracture toughness depends on the position of notch-tip with respect to the layers or interlayer interface due to changes in the grain size, particle volume fraction and residual stress pattern. The mechanical behaviour of the laminated composites has been compared with those of monolithic MoSi₂ and MoSi₂-based composite samples studied separately.