The Effect of TiC Additive with Al2O3-Y2O3 on the Microstructure and Mechanical Properties of SiC Matrix Composites

In this research, the SiC-matrix composite with different amounts of TiC (0, 2.5, 5, 7.5, and 10 wt%) supplemented with additives including 4.3 wt% Al2O3 and 5.7 wt% Y2O3 were utilized to initiate the required liquid phase. The sintering process was performed using pressureless sintering at      1900 °C for 1.5 hours under argon atmosphere. The composition and microstructure of the obtained composites were analyzed using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and Energy-Dispersive X-ray Spectroscopy (EDX). The results showed that TiC additives improved the densification of samples and impeded the growth of SiC grains. According to the phase analysis, the SiC was the main phase, while the TiC and YAG were characterized as partial phases. Additionally, due to the reaction of TiC and Al2O3, the composition of the liquid phase contained YAG and YAM. Assessments revealed that the microstructure and the final properties of composites were affected by density, produced phases and their distribution in the matrix, and grain size. According to the results, upon increasing the TiC up to 5 wt%, all the measured properties including density, hardness, elastic modulus, and fracture toughness improved and reached 97.40%, 26.73 GPa, 392 GPa, and 5.80 MPa.m1/2, respectively. However, with increasing the additives to more than 5 wt%, these properties deteriorated. Microscopic evaluations revealed that crack deflection and crack bridging mechanisms contributed to the fracture toughness of SiC ceramics.