Effect of TiO₂ addition on the properties of Ti₃Si(Al)C₂ based ceramics fabricated by reactive melt infiltration

In this paper, Ti₃Si(Al)C₂ based ceramics were fabricated by reactive melt infiltration (RMI) of TiC/TiO₂ preforms with liquid silicon. The microstructure, phase composition, and mechanical properties of the Ti₃Si(Al)C₂ based ceramics have been investigated to understand the effect of phase composition of the preforms on the formation mechanisms of Ti₃Si(Al)C₂. The preforms with different content of TiO₂ infiltrated at 1500 °C with liquid silicon for 1 h were composed of Ti₃Si(Al)C₂, Al₂O₃, TiC, TiSi_xAl_y and residual Al. The prior generated Al₂O₃ phases inhibited the dispersion of Ti₃Si(Al)C₂ phases, resulting in the drastically grain growth of Ti₃Si(Al)C₂. Subsequently, the microstructure with gradually increasing Ti₃Si(Al)C₂ grain size resulted in the decrease of the bending strength and fracture toughness of samples. When the content of TiO₂ reached 20 wt%, the bending strength reached the maximum, 326.6 MPa. The fracture toughness attained the maximum, 4.3 MPa m^1/2, when the content of TiO₂ was 10 wt%.