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<p>Oxygen-induced microstructural evolution critically governs the long-term reliability of refractory multi-principal element alloys (RMPEAs) in extreme environments, where oxygen ingress during prolonged high-temperature service can drastically alter microstructural stability and mechanical performance, yet its atomic-scale mechanisms remain poorly understood. Here, oxygen’s dual role in NbZrTi-based RMPEAs is systematically revealed through aging experiments at 650&#xa0;℃ for 48 and 168&#xa0;h, combined with multiscale characterization. High-oxygen alloys (3&#xa0;at.% O) exhibited multi-phase precipitation, including Zr-O-enriched hexagonal close-packed and dual body-centered cubic phases (Zr + Ti-O-rich and Nb + Ti-rich), governed by oxygen redistribution and thermodynamic stabilization. Contrary to conventional precipitation hardening, oxygen segregation gradients at the grain boundaries induced lattice distortion mitigation in the matrix, leading to a two-stage age-softening behavior: rapid initial hardness reduction (20% within 48&#xa0;h) followed by a plateau regime. The interplay between oxygen-mediated phase separation and concentration-dependent solute partitioning highlights the delicate balance required to optimize RMPEAs for high-temperature applications. These findings establish oxygen concentration thresholds and grain boundary engineering as critical design parameters for RMPEAs, enabling simultaneous optimization of radiation resistance and century-scale stability in next-generation nuclear reactor structure materials.</p> Graphical abstract <p></p>

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Oxygen-driven precipitate evolution and age-softening behavior in NbZrTi refractory multi-principal element alloys

  • 期刊论文

  • 发表日期：

    2025年7月10日

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  • Zheng-Xiong Su,
  • Hao-Yu Shi,
  • Yu-Xi Bai,
  • Xiao-Yang Zhou,
  • Ping Zhang,
  • Jian-Qiang Wang,
  • Deng-Jiang Fu,
  • Jin-Xue Yang,
  • Ke Jin,
  • Hang Zang,
  • Rui Gao,
  • Chen-Yang Lu

摘要

Oxygen-induced microstructural evolution critically governs the long-term reliability of refractory multi-principal element alloys (RMPEAs) in extreme environments, where oxygen ingress during prolonged high-temperature service can drastically alter microstructural stability and mechanical performance, yet its atomic-scale mechanisms remain poorly understood. Here, oxygen’s dual role in NbZrTi-based RMPEAs is systematically revealed through aging experiments at 650 ℃ for 48 and 168 h, combined with multiscale characterization. High-oxygen alloys (3 at.% O) exhibited multi-phase precipitation, including Zr-O-enriched hexagonal close-packed and dual body-centered cubic phases (Zr + Ti-O-rich and Nb + Ti-rich), governed by oxygen redistribution and thermodynamic stabilization. Contrary to conventional precipitation hardening, oxygen segregation gradients at the grain boundaries induced lattice distortion mitigation in the matrix, leading to a two-stage age-softening behavior: rapid initial hardness reduction (20% within 48 h) followed by a plateau regime. The interplay between oxygen-mediated phase separation and concentration-dependent solute partitioning highlights the delicate balance required to optimize RMPEAs for high-temperature applications. These findings establish oxygen concentration thresholds and grain boundary engineering as critical design parameters for RMPEAs, enabling simultaneous optimization of radiation resistance and century-scale stability in next-generation nuclear reactor structure materials.

Graphical abstract