Co-authors​ :

 Guangda GUO (CHINA) 

Continuous SiC fiber-reinforced SiC matrix composites (SiC/SiC) have attracted significant interest for high-temperature applications due to their exceptional chemical, physical, and mechanical properties in harsh environments. Enhancing the density of the matrix in SiC/SiC composites can significantly enhance their mechanical properties while mitigating oxidation damage to the fiber and interphase. SiC/SiC composites prepared by reactive melt infiltration (RMI) demonstrate exceptional properties, however, residual Si have a detrimental impact on the high-temperature mechanical properties, and addressing the issue of high-content residual Si aggregated distribution remains a crucial research hotspot in order to unlock full application potential of SiC/SiC composites by RMI. When the residual Si form large blocks inside the composites, a sharp decline in properties of SiC/SiC will occur due to bulk Si with poor mechanical properties will be a source of failure. To mitigate this issue and improve the properties of SiC/SiC composites, the Si phase in the matrix is required to be uniformly separated by a SiC phase that plays a role in dispersion strengthening, which can be achieved based on two ways: 1) SiC particles slurry impregnation or casting, and 2) C-Si reaction. In this work, a special porous carbon (Cg) is successfully synthesized and introduced into the porous 2D SiC/SiC composites. The unique pore structure of the SiC/SiC-Cg is thoroughly analyzed, along with its liquid Si infiltration process. The difference in coefficient of thermal expansion between SiC and Cg can cause the C particles detach from the Cg skeleton and react with Si to create SiC. This process effectively separates residual Si and helps alleviate the negative effects of residual Si aggregation. The microstructure and phase distribution of SiC/SiC composites are investigated. The as-received SiC/SiC composites possess a density of 2.94 g/cm3 with open porosity of 1.23%, and a flexural strength of 808.7±10.2 MPa, a fracture toughness of 25.5±1.8 MPa·m1/2, a tensile strength of 317.4±12.4 MPa and a proportional ultimate stress of 157.33±4.1 MPa. The microstructure and formation mechanism of the SiC-Si hybrid matrix are thoroughly investigated, the mechanical properties of the highly dense SiC/SiC are analyzed, and the detailed study on the failure behavior of composites is carried out. Acoustic emission and digital image correlation technology are used to study the special mechanical behavior of composites.