Uniting superior mechanical properties with oxidation resistance in a refractory high-entropy alloy via Cr and Al alloying

Refractory high-entropy alloys (RHEAs) have attracted considerable interest due to their elevated melting points and remarkable softening resistance. Nevertheless, the ambient-temperature brittleness and inadequate high-temperature oxidation resistance commonly limit the application of the body-centered-cubic (BCC) RHEAs. In this study, we achieved a Ti₄₁V₂₇Hf_11.5Nb_11.5Cr₃Al₆ RHEA with a desirable yield strength of ∼1178 MPa and tensile ductility of ∼19.5 %. Exploring the underlying mechanisms, we demonstrated that Cr and Al alloying induced a nanoscale spinodal structure and generated a significant lattice misfit, resulting in a notable strengthening effect and pinning behavior. Meanwhile, dislocation configurations involving loops and cross slips were stimulated by pinning, serving a reliable strain-hardening capability to large strains. Significantly, Cr and Al alloying improved oxidation resistance and prevented severe spallation at high temperatures by forming protective oxide layers. These results provide opportunities to design novel RHEAs.