Mechanical behaviours of hot-pressed rare-earth oxide (RE = Y and La)-doped TaB2-SiC composites

In this study, TaB2-20 vol% SiC composites with and without rare-earth oxides (RE2O3, RE = Y and La) were fabricated via hot pressing at or above 1800 degrees C. 3 vol% RE2O3 additions improved the sinterability of TaB2-SiC composite and resulted in a finer microstructure in addition to the crystalline RE2Si2O7 grain-boundary phase. The shear and Young's moduli as well as hardness of the composites decreased with RE2O3 additives. Conversely, the fracture toughness of the composites increased with RE2O3 additives and the toughening effect was better for La2O3 than for Y2O3. On the other hand, the additions of RE2O3 substantially enhanced the flexural strength and the strengthening effect was significantly stronger for Y2O3 than for La2O3, the strengthening was ineffective at or above 1400 degrees C, however. Additionally, the temperature dependence of strengths varied with and without RE2O3 additions, as a result of the difference in the chemistry of the intergranular phases.

Automated summary

In this study, TaB2-SiC composites with and without rare-earth oxides were fabricated and the effects of rare-earth oxides on their mechanical properties were investigated. The results showed that the addition of rare-earth oxides improved the sinterability, microstructure, and fracture toughness of the composites, but decreased the shear and Young's moduli as well as the hardness. Additionally, the effects of rare-earth oxides on the strength and toughening of the composites were temperature-dependent.