Effects of TaSi2 addition on room temperature mechanical properties of ZrB2-20SiC composites

The effects of TaSi2 addition on the room temperature mechanical properties of ZrB2-20SiC (volume fraction, %) composite were investigated. Dense ZrB2-20SiC-xTaSi2 (x = 3, 6, 10) composites were prepared by hot pressing the mixture of ZrB2, SiC and TaSi2 powders at 1850-1900 °C under 30 MPa in flowing Ar. In the as-prepared composites, apart from ZrB2, SiC and TaSi2, (Zr,Ta)B2 solid solution also existed around ZrB2 grains. It became a continuous layer and the thickness increased gradually with the increase of TaSi2 content. When the addition of TaSi2 was within the range of 3-10%, Vickers hardness of ZrB2-20SiC reduced slightly by about 1-2 GPa, but the flexural strength and fracture toughness increased simultaneously by more than 35%. These phenomena could be attributed to the relatively low hardness of TaSi2, and the decrease of ZrB2 grain size as well as the presence of a continuous (Zr,Ta)B2 solid solution layer around ZrB2 grains.