High-temperature strength and toughness behaviors for reaction-bonded SiC ceramics below 1400 °C

High-temperature strength and toughness behaviors of reaction-bonded SiC ceramics with 12 and 26 vol.% of free Si were investigated. The flexural strength and fracture toughness started to increase at 1000 °C and reached a maximum at 1300° and 1330 °C before a sharp drop, respectively. The transition from transgranular to intergranular fracture is considered to lead to the slight increase of strength and toughness from room temperature to 1000 °C, while the plastic deformation of free Si contributes to the great increase above 1000 °C. However, too high a temperature will result in the extreme softening of free Si and therefore decrease strength and toughness.