| About this Abstract |
| Meeting |
10th International Symposium on Superalloy 718 and Derivatives (2023)
|
| Symposium
|
Superalloy 718 and Derivatives
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| Presentation Title |
Preferential γ' Precipitation on Coherent Annealing Twin Boundaries in Alloy 718 |
| Author(s) |
Semanti Mukhopadhyay, Fei Xue, Hariharan Sriram, Robert W. Hayes, Emmanuelle A. Marquis, Yunzhi Wang, Michael J. Mills |
| On-Site Speaker (Planned) |
Michael J. Mills |
| Abstract Scope |
Early strain localization parallel and adjacent to annealing twin boundaries (ATBs) have been reported in several superalloys. While strain localization is generally attributed to local shear stresses developed near ATBs due to elastic anisotropy, it is presently unclear if local microstructural features near ATBs might also play an important role. Precipitate-free zones (PFZ) parallel to ATBs in a γ''–strengthened alloy 945X have been reported and were found to influence strain localization in the alloy greatly. However, it is unclear if such PFZs near ATBs occur in other superalloys, potentially influencing strain localization. The present work investigates microstructures near ATBs in a Ni-based superalloy - 718, strengthened by both γ' and γ'' phases. This work aims to characterize the precipitates present at the ATBs and to explore if a microstructural cause for strain localization exists in this alloy. Based on our characterization experiments, Alloy 718 shows a high density of herringbone-like γ^'-γ'' precipitates at ATBs. However, the ATBs exhibit a much higher fraction of γ' (25.3±2.8%) than γ'' (18.4±2.4%), ultimately causing the coprecipitate fraction at ATBs to be as high as 43%. We also report a local HCP-phase at the ATBs within γ' precipitates exhibiting Nb segregation and Al depletion. On the contrary, no appreciable change in the ATB composition was observed within γ''. Finally, our characterization experiments also reveal precipitate-free zones parallel and adjacent to the ATBs in alloy 718. |
| Proceedings Inclusion? |
Definite: At-meeting proceedings |