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<p>The ongoing push to elevate operating temperatures in aerospace gas turbine engines – driven by goals of enhanced fuel efficiency and reduced CO<sub>2</sub> emissions – mandates advancements in the creep resistance of Ni- and Co-based superalloys, which are integral for critical engine components. This study elucidates the role of stress assisted localized phase transformations in the creep properties of these alloys. By leveraging chemo-mechanical coupling, self-healing <i>γ</i>′ precipitates are designed to immobilize planar defects, thereby increasing creep resistance. Employing advanced characterization techniques such as high-resolution Scanning Transmission Electron Microscopy&#xa0;(HR-STEM), in conjunction with atomistic simulations and thermodynamic calculations, novel deformation pathways facilitated by <i>χ</i> local phase transformation (LPT) strengthening have been uncovered; notably, the formation of <i>χ</i> nano-laths through microtwinning and superlattice intrinsic stacking fault (SISF) shearing. This study highlights critical insights into the compositional boundaries necessary for optimizing LPT strengthening while avoiding deleterious bulk formation of <i>η</i>/<i>χ</i> phases. These advancements will guide the design of new alloys maximizing high-temperature creep strength for advanced aerospace applications.</p>

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Stress-dependent χ phase transformation in a Ni-based superalloy

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月14日

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  • Ashton J. Egan,
  • N. S. Harsha Gunda,
  • Longsheng Feng,
  • Maryam Ghazisaeidi,
  • Yunzhi Wang,
  • Sammy Tin,
  • Michael J. Mills

摘要

The ongoing push to elevate operating temperatures in aerospace gas turbine engines – driven by goals of enhanced fuel efficiency and reduced CO2 emissions – mandates advancements in the creep resistance of Ni- and Co-based superalloys, which are integral for critical engine components. This study elucidates the role of stress assisted localized phase transformations in the creep properties of these alloys. By leveraging chemo-mechanical coupling, self-healing γ′ precipitates are designed to immobilize planar defects, thereby increasing creep resistance. Employing advanced characterization techniques such as high-resolution Scanning Transmission Electron Microscopy (HR-STEM), in conjunction with atomistic simulations and thermodynamic calculations, novel deformation pathways facilitated by χ local phase transformation (LPT) strengthening have been uncovered; notably, the formation of χ nano-laths through microtwinning and superlattice intrinsic stacking fault (SISF) shearing. This study highlights critical insights into the compositional boundaries necessary for optimizing LPT strengthening while avoiding deleterious bulk formation of η/χ phases. These advancements will guide the design of new alloys maximizing high-temperature creep strength for advanced aerospace applications.