Influence of annealing on the mechanical properties of SiC–Si composites with sub-micron SiC microstructures

The influence of annealing temperature (1000, 1100 and 1200°C) on the mechanical properties of SiC–Si composites has been evaluated. Three SiC powders with particle sizes in the range of 0.24 to 0.7 μm were used to produce the composites. Before application the SiC powders were treated with hydrofluoric acid to remove the extent of SiO2. With this treatment a successful infiltration of green-bodies especially produced of SiC powder with a mean particle size of 0.24 μm was possible. The bending strength decreased with decreasing SiC starting particle size as well as with increasing annealing temperature. However, the fracture toughness was independent on SiC starting particle size and annealing temperature. XRD diffraction analysis showed that internal stress, expressed by broadening of XRD peaks, is low and had no effects on the mechanical properties of the composites.