Computational design of castable WTaNb-C eutectic refractory medium-entropy composite with ultrahigh strength at 2000°C

We present a novel WTaNb-C eutectic refractory medium-entropy composite with fully lamellar BCC/M₂C microstructure, designed via pseudo-binary strategy to resolve the strength-castability trade-off in ultrahigh-temperature materials. The as-cast composite achieves record yield strength of 559 MPa at 2000 °C. Semi-coherent BCC/M₂C interfaces enable Hall-Petch-like strengthening and thermal stability, while BCC_II precipitates within M₂C lamellae enhance strain accommodation through interfacial stress redistribution. The composite demonstrates 3.55× higher yield strength at 2000 °C, 17-29% density reduction, and 45–52% cost savings over Ta-10W and W-25Re, offering a transformative solution for aerospace components requiring simultaneous thermomechanical robustness and near-net-shape formability. Impact statement: This study introduces a BCC/M₂C fully eutectic structure resolving strength-castability trade-off in ultrahigh-temperature materials, achieving record 559 MPa yield strength at 2000°C via high-density interfaces and BCC_II precipitates.