Effect of high temperature heat treatment on ZrB2–SiC composites added with Yb2O3

ZrB2-20 vol% SiC composites added with 3 vol% Yb2O3 were hot-pressed at 1900 °C, and then heat-treated at 2000 °C in argon. The effect of heat treatment on phase composition, microstructure, and mechanical properties of the composites was investigated. Results showed that the high temperature heat treatment led to the depletion of Yb-containing phases by decomposition or evaporation, the formation of some pores at multiple-grain junctions, significant microstructural coarsening with the increase of ZrB2 grain size from ∼1.9 μm to ∼4.8 μm, and the change of fracture mode from mixed inter/transgranular to fully transgranular. In addition, Vickersʹ hardness, fracture toughness and flexural strength were severely degraded after heat treatment.