Polycrystalline LaB6-ZrB2 composites with various contents of ZrB2 were fabricated by vacuum hot-pressed sintering. For the LaB6-21wt%ZrB2eutectic composite, the hardness, flexural strength and fracture toughness were 93.0HRA, 330.0MPa and 3.70MPam1/2, respectively. The results showed that the hardness and flexural strength of LaB6-ZrB2 polycrystals were enhanced with increasing ZrB2 content, but the fracture toughness first increased then arrived at a peak value which corresponded to a ZrB2 content of 21wt%. The microstructure revealed an improved densification due to additions of ZrB2. The fracture morphology showed a tendency to change from intergranular to transgranular with increasing ZrB2 content.

Mechanical Properties of LaB6-ZrB2 Composites. Min, G., Gao, R., Yu, H., Han, J.: Key Engineering Materials, 2005, 297-300[III], 1630-6