Correlation of C/C preform density and microstructure and mechanical properties of C/C-ZrC-based ultra-high-temperature ceramic matrix composites

Understanding the correlation of C/C preform density and microstructure and properties of the resulting composites is of great importance for the fast and economical fabrication of ultra-high-temperature ceramic matrix composites by reactive melt infiltration. In this paper, C/C-ZrC composites were prepared by eutectic Zr-Si alloyed melt infiltration using different density C/C composite preforms, and the influence of C/C preform densities on the microstructure and mechanical properties of the composites was investigated. The results showed that the densities of the composites decreased with the increase of the C/C preform densities while the open porosities always kept at small values. The C/C-ZrC composites were generally composed of carbon, ZrC phase, and Zr2Si phase. The microstructure and phase composition of the composites were greatly influenced by C/C preform densities. Flexural strength of the composites initially increased with C/C preform densities, and then decreased reversely. The C/C-ZrC composite reached its highest flexural strength, 241 MPa, when the C/C preform density was 1.28 g/cm3. This work revealed the correlation of C/C preform density and microstructure and mechanical properties of C/C-ZrC composites, and will provide a guidance for performance optimization of reactive melt infiltrated ultra-high temperature ceramic matrix composites. The (a): densities and open porosities; (b): XRD patterns; (c): flexural strength of the C/C-ZrC composites prepared by C/C composite preforms with different densities