Hot-pressed ZrB2-SiC-YSZ composites with various yttria content: Microstructure and mechanical properties

ZrB2-10vol%SiC-20 vol%YSZ composites were prepared by hot-pressed sintering with yttria content ranging from 2 mol% to 8 mol% in YSZ. The phase constitution, microstructure and mechanical properties of the composites were found to be strongly dependent on the yttria content. The average grain size became bigger for the composites with higher yttria content. When the yttria content was below 3 mol%, there is no cubic zirconia in the polished surface of composites, and the flexural Strength of the composites was above 740 MPa. With the increase in yttria content, the fracture toughness fell down from 6.4 Mpa m(1/2) to 5.6 MPa m(1/2). Vickers' hardness of the hot-pressed composites varied above 18 GPa without obvious effect of the yttria content. (C) 2008 Elsevier B.V. All rights reserved.