High-throughput screening of Ta _{1− <i>x</i>} Hf _<i>x</i> C _<i>y</i> ceramics for mechanical and oxidation performance optimization for ultra-high-temperature applications

Ta_1-xHf_xC_y ternary ceramics are highly valued in hypersonic vehicles and a precise composition design is promising to simultaneously reduce their intrinsic brittleness and enhance protective capability during oxidation. Herein, the composition-dependent mechanical properties and oxidation behaviors of Ta_1-xHf_xC_y ternary ceramics over a broad composition range (x=0.22 to 0.78, y=0.66 to 1.00) are efficiently investigated through combinatorial and high-throughput experimentation to pave the way for targeted development of novel carbide candidates. Evolution trends in hardness and modulus reveal that the composition range with x=0.22 to 0.60, y= 0.80 to 1.00 is promising to reach an optimal balance between hardness and toughness, which results from competing effects between solid solution strengthening and bonding characteristic transition. High-throughput oxidation elucidates the phase constitution and compactness of oxidation products with various Ta/Hf distributions and temperatures. The accurate compositional range for the formation of a single-phase dense Hf-Ta-O compound layer shifts to a Ta-rich region (x=0.50 to 0.60) due to the preferential formation of Ta-doped HfO₂ and the structural characteristics of Hf-Ta-O compounds that accommodate compositional deviations. Regarding the broad compositional space of Ta_1-xHf_xC_y, the effects of composition on both mechanical properties and oxidation behavior are systematically investigated, providing fundamental design guidelines and an optimal composition range that holds significant promise for application in subsequent research.