Effects of SiC contents on the microstructure and mechanical properties of Al4SiC4-SiC ceramic composites

High dense Al4SiC4-SiC ceramic composites with different SiC contents were hot pressed using self-synthesized Al4SiC4 and commercial SiC powders without any sintering additives. The effect of SiC contents on the densification, microstructure, and mechanical properties of Al4SiC4-based ceramics was investigated. The anisotropic growth of Al4SiC4 grains was inhibited by the pinning effect of the introduced SiC particles, while the weakly bonded interfaces were formed due to the thermal expansion mismatch between Al4SiC4 and SiC. As a consequence, the mechanical properties of Al4SiC4-based ceramics were improved significantly. With the SiC contents increasing from 0 to 30 wt%, the flexural strength increased from 314 +/- 7 to 466 +/- 18 MPa and the fracture toughness increased from 4.8 +/- 0.4 to 7.3 +/- 0.3 MPa m1/2, respectively. The flexural strengths of Al4SiC4-SiC composites at elevated temperatures were also tested under an argon atmosphere. No strength degradation of Al4SiC4-SiC composites was observed at 1200 degrees C and a high strength retention rate of 96.3 % at 1400 degrees C was obtained. The above results demonstrate the application prospects of Al4SiC4-SiC ceramics as high-temperature structural materials.