Journal
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
Volume 49A, Issue 9, Pages 4186-4198Publisher
SPRINGER
DOI: 10.1007/s11661-018-4701-5
Keywords
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Funding
- NASA's Aeronautics Research Mission Directorate (ARMD) Convergent Aeronautics Solutions Project
- NASA's Advanced Air Transport Technology (AATT) Project Office (ARMD)
- National Science Foundation
- DMREF program [1534826]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [1534826] Funding Source: National Science Foundation
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In this study, local chemical and structural changes along superlattice intrinsic stacking faults combine to represent an atomic-scale phase transformation. In order to elicit stacking fault shear, creep tests of two different single crystal Ni-based superalloys, ME501 and CMSX-4, were performed near 750 degrees C using stresses of 552 and 750 MPa, respectively. Through high-resolution scanning transmission electron microscopy (STEM) and state-of-the-art energy dispersive X-ray spectroscopy, ordered compositional changes were measured along SISFs in both alloys. For both instances, the elemental segregation and local crystal structure present along the SISFs are consistent with a nanoscale gamma' to D0(19) phase transformation. Other notable observations are prominent gamma-rich Cottrell atmospheres and new evidence of more complex reordering processes responsible for the formation of these faults. These findings are further supported using density functional theory calculations and high-angle annular dark-field (HAADF)-STEM image simulations.
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