Pressureless sintering of SiC-TiC composites with improved fracture toughness

Abstract

Composites of SiC-TiC containing up to 45 wt% of dispersed TiC particles were pressureless sintered to ∼97% of theoretical density at temperatures between 1850°C and 1950°C with Al2O3 and Y2O3 additions. An in situ-toughened microstructure, consisted of uniformly distributed elongated α-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 ≥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·m1/2, owing to the bridging and crack deflection by the elongated α-SiC grains.