Synthesis, microstructure and mechanical properties of reaction-infiltrated TiB2–SiC–Si composites

TiB2–C preforms formed with different compositions and processing parameters were reactively infiltrated by Si melts at 1450 °C to fabricate TiB2–SiC–Si composites. Phase constituent and microstructure of these composites were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The resulting composites are generally composed of TiB2 and reaction-formed β-SiC major phases, together with a quantity of residual Si. Unreacted carbon is detected in the samples with a starting composition of 2TiB2 + 1C formed at higher pressure and in all of the ones at the composition of 1TiB2 + 1C. The distribution of these phases is fairly homogeneous in microstructure. TiB2–SiC–Si composites show good mechanical properties, with representative values of 19.9 GPa in hardness, 395 GPa in elastic modulus, 3.5 MPa m1/2 in fracture toughness and 604 MPa in bending strength. The primary toughening and strengthening mechanism is attributed to the crack deflection of TiB2 particles.

Research highlights▶ The influence of forming pressure and debinding temperature of preforms as well as infiltrating atmosphere on the phase constituents of resultant composites was investigated on the base of XRD analyses. ▶ TiB2–SiC–Si composites show good mechanical properties, with representative values of 19.9 GPa in hardness, 392 GPa in elastic modulus, 3.5 MPa m1/2 in fracture toughness and 639 MPa in bending strength. ▶ The primary toughening and strengthening mechanism is attributed to the crack deflection of TiB2 particles.