Microstructure and fracture properties of biomorphic SiC

An investigation was made into the microstructure and high temperature mechanical properties of eucalyptus biomorphic SiC fabricated by pyrolizing a piece of eucalyptus wood and its infiltration with molten Si. The final product is a Si/SiC composite, which reproduces anisotropic microstructure of the wood. The elastic modulus was found to be constant up to 1000 °C. The compressive strength decreased with the rise of temperature, but the flexure strength was constant up to 1350 °C. At temperature close to the silicon melting point, the material strength was significantly reduced, the silicon phase has been alloyed to play an important role in carrying the load in compressive stress, but in flexure stress the silicon flows within the grain, reducing the connectivity in the SiC network. Residual carbon, oxidized at high temperature, creates voids that reduce the effective section and propagate internal cracks. The plastic deformation of Si at high temperature enhances the fracture toughness of the material.