Enhancing creep resistance of lightweight refractory multi-principal element alloys via trace Y2O3 addition

Refractory multi-principal element alloys (RMPEAs) are promising candidates for next-generation high-temperature structural materials due to their excellent thermal stability and high-temperature strength, yet their long-term creep resistance remains a key challenge. Here, we show that introducing trace Y 2 O 3 (0.2 wt%) into lightweight Ti 45 V 45 (AlCrMo) 10 RMPEAs significantly enhances creep resistance. Tensile creep tests conducted at 650 and 700 °C under 100–200 MPa, combined with detailed microstructural characterization, reveal that the Y 2 O 3 -containing alloy exhibits a lower minimum creep rate and a higher activation energy (285 kJ mol −1 ) than the Y 2 O 3 -free alloy (246 kJ mol −1 ). The stress exponent (n ≈ 2–3) indicates that creep deformation in both alloys is governed by a solute-drag-controlled viscous glide mechanism. Intrinsic diffusion calculations revealed that the harmonic mean of the five elemental diffusion coefficients reasonably predicts creep behavior, with sluggishly diffusing V potentially contributing significantly to solute drag. The dispersed Y 2 O 3 particles promote dislocation accumulation, increase geometrically necessary dislocation density, and raise the fraction of low-angle grain boundaries. Concurrently, these particles contribute to grain-boundary stabilization through Zener pinning, thereby restricting grain-boundary migration and dynamic recrystallization during creep. These effects stabilize the deformation substructure and thereby significantly enhance the creep resistance. This work provides valuable insights for the design of novel creep-resistant lightweight alloys.