Mechanical properties and microstructure of an Al2O3–SiC–TiC composite

The mechanical properties and microstructure of a hard, electrodischarge-machinable composite, Al2O3–SiC–TiC, were studied. The material was fabricated by hot pressing 46.1 vol.% Al2O3 powder, 30.9 vol.% SiC whiskers and 23.0 vol.% TiC powder. Significant reaction occurred between the Al2O3 and SiC during processing. The resultant composite consisted of nearly unreacted TiC particles, Al2O3, plus smaller concentrations of SiC, mullite and possibly a mixture of Al–Si–O–C. The composite exhibited at room temperature an elastic modulus of 409.6±0.5 GPa, microhardness values of 19–32 GPa, indentation fracture toughness (KIC) of 9.6±0.6 MPa(m)0.5, compressive strength as high as 2.8 GPa and fracture strength in bending of ≈680–825 MPa.