Outstanding high-temperature strength of carbide-reinforced Re0.04Hf0.1Ta1.6Wx(TaC)y refractory medium-entropy alloys with a eutectic structure

To achieve a better balance between room-temperature compressive plasticity and ultra-high-temperature strength in carbide-reinforced refractory alloys, Re–Hf–Ta–W-based refractory medium-entropy alloys with varied W and TaC contents were designed. Three alloys were prepared by vacuum arc melting, and their phase constitution, microstructure, and compressive properties from room temperature to 1750°C were systematically characterized. The alloys were mainly composed of a body-centered cubic (BCC) metallic phase and M2C-type hexagonal close-packed (M2C-HCP) carbide, forming eutectic composite microstructures. Increasing TaC content refined the eutectic structure and increased the carbide volume fraction from 32.5% to 40.7%, while increasing W content promoted W enrichment in the BCC phase, consistent with an increased room-temperature strengthening tendency of the BCC phase. At room temperature, the alloys exhibited peak compressive strengths of 2206–2430 MPa and fracture strains of 10.2%–17.2%. At 1750°C, the alloys retained peak compressive strengths of up to 1026 MPa. The favorable combination of room-temperature compressive deformability and ultra-high-temperature strength is associated with W enrichment of the BCC phase, carbide load bearing, BCC/M2C-HCP interfacial constraint, and defect-mediated local strain accommodation within the carbide.