Pressureless sintering of SiC-TiC composites with improved fracture toughness

Composites of SiC-TiC containing up to 45 wt% of dispersed TiC particles were pressureless sintered to similar to 97% of theoretical density at temperatures between 1850 degreesC and 1950 degreesC with Al2O3 and Y2O3 additions. An in situ-toughened microstructure, consisted of uniformly distributed elongated alpha -SiC grains, matrixlike TiC grains, and yttrium aluminum garnet (YAG) as a grain boundary phase, was developed via pressureless sintering route in the composites sintered at greater than or equal to 1900%C. The fracture toughness of SiC-30 wt% TiC composites sintered at 1900%C for 2 h was as high as 7.8 MPa.m(1/2), owing to the bridging and crack deflection by the elongated alpha -SiC grains. (C) 2000 Kluwer Academic Publishers.