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

Abstract

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.