High strain rate response and mechanical performance of tantalum carbide–hafnium carbide solid solution

Ultra-high temperature ceramics (UHTCs) based on the solid solution TaxHf1-xC have shown great promise as materials for extreme environments (>2500 °C) due to their improved thermo-mechanical properties. However, their dynamic response under high-impact loading remains unknown. In this study, we investigate the dynamic impact behavior and fracturing evolution of TaxHf1-xC samples (with x = 0, 0.2, 0.5, 0.8, and 1) at a strain rate > 103 s-1 using the Split Hopkinson Pressure Bar (SHPB) test. Among the different compositions, Ta0.5Hf0.5C exhibits the highest compressive strength of 1870 MPa, representing a 36% improvement over TaC and 54% over HfC. High frame rate videos and deformation analysis reveal that Ta0.5Hf0.5C, characterized by extensive Ta–Hf bonding, significantly reduces the crack propagation rate by approximately 1435% compared to TaC and 4050% compared to HfC. This effect is attributed to the dislocation pile-ups, nano-twin formation, inter grain twisting exhibited mostly along {111} plane as Hf substitutes Ta in TaxHf1-xC samples. Further, the surface energy is least for {111} plane eliciting the higher probability for bypassing crack propagation along this plane in TaxHf1-xC. The exceptional damage tolerance and improved mechanical properties of Ta0.5Hf0.5C, compared to other solid-solution TaxHf1-xC compositions, make it an extraordinary structural material for hypersonic applications. These findings provide valuable insights into the dynamic behavior of UHTCs and highlight the potential of Ta0.5Hf0.5C as a superior material for extreme environments requiring high-impact resistance.