Stress-dependent <em>χ</em> phase transformation in a Ni-based superalloy

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.. Authors: Egan, Ashton J. [Friedrich-Alexander University Erlangen-Nuremberg (Germany)] (ORCID:0000000347177279); Gunda, Naga Sri Harsha [Indian Inst. of Technology (IIT), New Dehli (India)]; Feng, Longsheng [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000308453656); Ghazisaeidi, Maryam [The Ohio State University, Columbus, OH (United States)] (ORCID:0000000179492930); Wang, Yunzhi [The Ohio State University, Columbus, OH (United States)] (ORCID:000000033247297X). DOE Contract: AC52-07NA27344