| Laminated composites have been prepared by stacking
powder layers of : (i) MoSi2-20 vol% SiC composite and MoSi2-
3 wt% AI 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. |
