A novel refractory complex concentrated alloy with ultra-high strength at 1200°C

Herein, we introduced a novel equiatomic MoNbTaTiSi refractory complex concentrated alloy (RCCA) with unprecedented ultra-high-temperature capabilities. Owing to its hypoeutectic structure, consisting of dominating tetragonal β-Me₅Si₃ and minor hexagonal γ-Me₅Si₃ phases, each holding specific orientation relationships with a proeutectic bcc phase, the alloy showed excellent softening resistance up to 0.74T_m with a record-high specific yield strength of 135 MPa*cm³/g at 1200 °C, exceeding all known RCCAs. Though having moderate fracture toughness at room temperature (K_Q ≈ 7 MPa*m^1/2), the alloy also demonstrated superior tolerance to prolonged thermal impact and low 1 h-mass gain at 1200 °C, which ranked it among the most oxidation-resistant RCCAs. The results of this study offer guidelines for achieving unparalleled performance in RCCAs, targeting for applications at extreme temperatures.