Evolution on the microstructure and mechanical properties of the interface of crept SiC_f/SiC at intermediate temperatures

The creep rupture time of continuous silicon carbide fiber reinforced silicon carbide composite (SiC_f/SiC) is shortened at intermediate temperature (500~1000 ℃) inevitably, known as creep embrittlement. The mechanism primarily depends on the microstructure and the interfacial bonding state of the fiber/matrix interface. Therefore, present work investigated the creep embrittlement mechanisms of the domestic 2^nd-generation plain woven SiC_f/SiC (2D-SiC_f/SiC) under intermediate temperature. The interfacial microstructure evolution and mechanical properties was characterized by transmission electron microscopy (TEM) and micro-mechanical testing techniques respectively. The results indicate that a carbon-rich layer with pores appear on the fiber/interface side at 500℃. Spontaneous oxidation of the interface occurs at 800℃, while a thin SiO₂ layer fills the gap generated at the BN in- terface due to oxidation. When the temperature increases to 1000℃, oxygen elements are mainly distributed on the fiber/matrix side. The intermediate temperature embrittlement mechanism of 2D-SiC_f/SiC is closely associated with interface bonding state. The creep rupture time shows a clear inverse relationship with the interface bonding state, indicating that excessively strong interface bonding hinders related toughening mechanisms such as interface debonding and fiber pullout. Consequently, cracks directly penetrate the fiber, shortening the creep rupture time significantly.