Microstructure and mechanical behavior of Ta_xHf_1−xC–SiC fabricated by reactive hot‐pressing: Effect of Ta:Hf ratio

Abstract

TaxHf1–xC are promising candidates for many applications under harsh environments due to their unique properties. Up until now, low‐temperature densification is still a big challenge for these ceramics. Moreover, the effect of Ta:Hf ratio on microstructure development and mechanical behavior of the ceramics is not clear. In this work, highly dense TaxHf1−xC–SiC ceramics (x = 0.2, 0.4, 0.6, 0.8) were fabricated at 1700°C by a novel reactive hot‐pressing processing with 8 wt% Si as sintering aid, which present excellent mechanical properties. Fracture toughness of the ceramics is higher than 6.3 MPa·m1/2, with the highest toughness achieved in Ta0.6Hf0.4C–SiC (8.5 MPa·m1/2). With the increase of Ta content, hardness of the ceramics tends to increase, while the bending strength tends to decrease. The highest bending strength is achieved in Ta0.2Hf0.8C–SiC (637 MPa), and the highest hardness is achieved in Ta0.8Hf0.2C–SiC (17.6 GPa). This work lays the foundation for the composition design of TaxHf1−xC‐based ceramics and composites.