Abstract: Densification, β→α phase transformation, elongated SiC grain growth and microstructure, and mechanical properties, especially toughness, of in-situ
toughened SiC-YAG composites were investigated in detail. By using packing powders with same compositions as packed samples, the evaporation of Al₂O₃
was inhibited and full densification (>99% of theoretical density) of in-situ toughened SiC-YAG was achieved. The β→α phase transformation occurrs at
1950℃, however, remained β-SiC can be still found by XRD after post-heated at 2100℃ for 4h. The content of liquid phase and α-SiC seeds has no effect on the phase transformation rate.
Following phase transformation and grain growth during post-heating, further densification of in-situ SiC-YAG continues and the network microstructure
consisting of elongated SiC grains can be obtained. Finally, the SEPB fracture toughness achieved is near 7.0 MPa·m^1/2.

Key words: in-situ toughening, liquid phase sintering, Silicon Carbide, YAG