Abstract: Advanced structural materials with superb mechanical properties at ultrahigh temperatures are essential for aerospace and power-generation sectors. Refractory multi-principal element alloys (RMPEAs) are promising candidates, but they face challenges such as limited plasticity at room temperatures and insufficient strength at ultrahigh temperatures. In this work, we investigated the mechanical properties and microstructures of RMPEA reinforced with compositional complex carbides and demonstrated that tailoring the carbon content can significantly alter their microstructures and enhance mechanical properties. Specifically, the W₃₀Ta₃₀Mo₁₅Nb₁₅C₁₀ alloy achieved an ultrahigh strength of 896 MPa at 1600 °C and a plasticity of ∼8% at room temperatures. The strengthening effect arises from multi-principal element mixing and robust dislocation hindering at the phase interfaces between the carbides and the matrix, while the room temperature plasticity is attributed to crack buffering facilitated by the highly saturated solid solution matrix. Our study highlights the potential of compositional complex carbide to enhance the mechanical properties of RMPEAs, offering a promising approach for the development of advanced structural materials for ultrahigh temperature applications.

Key words: Refractory multi-principal element alloys, Compositionally complex carbides, Ultrahigh temperature, Room temperature, Mechanical property