About this Abstract |
| Meeting |
11th International Symposium on Superalloy 718 and Derivatives 2026: Legacy, Innovations, and Future Directions
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| Symposium
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Superalloy 718 and Derivatives 2026: Legacy, Innovations, and Future Directions
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| Presentation Title |
Revealing the γ′ Evolution During Controlled Cooling in Udimet720LI by Electron Microscopy with Complementary In-Situ SAXS |
| Author(s) |
Svetoslava Tsankova, Angela Quadfasel, Manuel Köbrich, Thomas Witulski, Andreas Stark, Cecilia Solís, Steffen Neumeier |
| On-Site Speaker (Planned) |
Svetoslava Tsankova |
| Abstract Scope |
Understanding the microstructural evolution of Ni-base superalloys during cooling from solution heat treatment is essential for optimizing turbine disc performance. In this study, a multi-technique approach was employed to investigate the γ ′ precipitation behavior of Udimet720LI under controlled continuous cooling conditions. A series of cooling experiments were conducted using a quenching dilatometer to apply precisely defined cooling rates between 0.7 and 100 °C/s. Selected experiments were complemented by synchrotron-based small-angle X-ray scattering (SAXS) measurements to track the precipitation kinetics during cooling.
Post-cooling microstructural characterization by scanning electron microscopy (SEM) showed that the grain size and primary γ ′ precipitates remained unaffected by the cooling rate, whereas the secondary γ ′ precipitates exhibited a strong cooling rate sensitivity. Their average diameter followed a power-law relationship with cooling rate, with an exponent consistent with diffusion-controlled growth. The size distributions were broad at slow cooling and narrow at high cooling rates, in agreement with the nucleation burst theory described in literature.
The SAXS analysis showed very good agreement with the SEM results and additionally revealed the presence of fine tertiary γ ′ precipitates, with diameters below the SEM resolution limit. These findings highlight the importance of combining SEM with in-situ SAXS to capture the full precipitate population across multiple size scales. By linking in-situ phase transformation kinetics with post-cooling microstructural analysis, this study establishes a framework for quantifying the relationship between cooling rate and γ ′ evolution and supports the development of optimized heat treatment strategies for turbine disc alloys. |
| Proceedings Inclusion? |
Definite: At-meeting proceedings |