Fabrication and characterisation of SiC fibre reinforced lithium–α-sialon matrix composites

Abstract Continuous SiC fibre unidirectionally-reinforced Li–α-sialon composites were produced by slurry infiltration followed by hot-pressing. The interface between the fibres and the matrix was characterised using scanning electron microscopy and energy dispersive X-ray spectroscopy. It was found that when Y2O3+Al2O3+ZrO2 was used as the sintering additive, the composite demonstrated brittle behaviour with no fibre pullout visible on the fracture surface because of the strong interface resulting from chemical reactions between the fibres and the matrix. When lithium aluminium silicate glass (LAS) or nitrogen-containing lithium aluminium silicate glass (NLAS) were used as sintering additives, the Nicalon fibres had a good chemical compatibility with the matrix. Some strengthening and toughening was observed but not to a significant extent because the matrix had a higher thermal expansion coefficient than the SiC fibre, and radial compressive stresses built up on the fibres caused a large interfacial frictional stress between the fibre and the matrix leading to a limited amount of fibre pullout.