Influence of pores distribution on fracture toughness of FeSi/Si3N4 composite

Abstract FeSi/Si 3 N 4 ceramic composite was fabricated by hot pressing technique, using α-Si 3 N 4 and Fe 3 Al. The toughening effect of Fe 3 Al on the Si 3 N 4 matrix is explained on the basis of microstructural characterizations and schematic representations. Results indicate that the reaction between α-Si 3 N 4 and Fe 3 Al results in the formation of FeSi and sialon phases at the interface. Both phases effectively restrain coalescence and movement of the gaseous reaction product, N 2 , retaining it in situ to form small separated pores. The dominant toughening effect of these pores reduces the interface bonding strength, consumes the crack propagation energy, and decreases the stress-concentration at the crack tip, thereby improving the fracture toughness of the matrix.