Microstructure and mechanical properties of Fe–Si alloy modified C/C–SiC composites

In this work, FeSi₂ modified C/C–SiC composites (C/C–SiC–FeSi₂) were fabricated using chemical vapor infiltration (CVI) combined with reactive melt infiltration (RMI) method. Then, C/C–SiC–FeSi₂ composites were further modified using FeSi95, FeSi85 and FeSi75 alloys as reactive melts. Effects of different FeSi₂ contents on microstructural and mechanical properties of C/C–SiC–FeSi₂ were investigated. With the increase in FeSi₂ content, cracks inside FeSi₂ phase in composites gradually increased due to thermal mismatch with other phases. The graphitization was observed in C/C region, and its area increased with the increase in the content of FeSi₂ in composites. Mechanical properties were significantly improved for appropriate content of FeSi₂, e.g., when FeSi95 and FeSi85 were used. Bending strength of C/C–SiC–FeSi₂ increased by 78% when FeSi95 was used, whereas fracture toughness increased by 112.5% compared to those of C/C–SiC. However, when FeSi₂ content was high, the fiber in material graphitized. Therefore, the performance of the material was significantly degraded.