High-temperature bending strength, internal friction and stiffness of ZrB_2-20 vol% SiC ceramics

摘要

Dense ZrB_2-20 vol% SiC ceramics (ZS) were fabricated by hot pressing using self-synthesized high purity ZrB_2 and commercial SiC powders as raw materials. The high temperature fiexural strength of ZS and its degradation mechanisms up to 1600 °C in high purity argon were investigated. According to the fracture mode, crack origin and internal friction curve of ZS ceramics, its strength degradation above 1000 °C is considered to result from a combination of phenomena such as grain boundary softening, grain sliding and the formation of cavitations and cracks around the SiC grains on the tensile side of the specimens. The ZS material at 1600 °C remains 84% of its strength at room temperature, which is obviously higher than the values reported in literature. The benefit is mainly derived from the high purity of the ZrB_2 powders.