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

Abstract

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 °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 °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.