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Post hot-deformation precipitation behavior of γ′ phase in VDM® alloy 780 under varying cooling rates and aging temperatures: An in situ high energy XRD study

Fritton M, Nagel O, Kümmel F, Stark A, Hafez-Haghighat M, Gehrmann B, Neumeier S, Gilles R (2025)

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Publication Type: Journal article

Publication year: 2025

Journal

Book Volume: 1037

Article Number: 182111

DOI: 10.1016/j.jallcom.2025.182111

Abstract

The performance of polycrystalline Ni-based superalloys is largely determined by the fraction and size of the intermetallic hardening phases, such as the γ′ phase. Understanding the evolution of the γ′ precipitate size and volume fraction during the complex thermomechanical process chain is essential for optimizing the mechanical properties of polycrystalline Ni-based superalloys. In this study, the high temporal resolution of in situ synchrotron X-ray diffraction at elevated temperatures was used to monitor γ′ evolution in VDM® Alloy 780 during cooling and subsequent aging heat treatments in real time. To simulate the industrial forging process, the alloy was initially subjected to compressive deformation at 1000 °C. In the first part of the study, immediately after hot forming, three different cooling rates (10 °C/min, 100 °C/min, and 1000 °C/min) were applied to analyse the in situ evolution of γ′ precipitation. The resulting γ′ phase fraction was highest at the slowest cooling rate, yet even the fastest cooling rate did not completely suppress precipitation. In the second part of the study, the age-hardening response of the alloy was examined at holding temperatures of 720 °C and 800 °C for five hours each. The evolution of the γ′ volume fraction, precipitate size, and lattice parameter was monitored in situ by XRD. After aging, γ′ volume fractions of 15 % and 19 % were obtained, with average precipitate sizes of 9 nm and 18 nm, respectively. The prior deformation enhanced γ′ formation at 720 °C compared to literature data. Complementary Transmission Electron Microscopy (TEM) measurements confirmed precipitate sizes consistent with the diffraction data.

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How to cite

APA:

Fritton, M., Nagel, O., Kümmel, F., Stark, A., Hafez-Haghighat, M., Gehrmann, B.,... Gilles, R. (2025). Post hot-deformation precipitation behavior of γ′ phase in VDM® alloy 780 under varying cooling rates and aging temperatures: An in situ high energy XRD study. Journal of Alloys and Compounds, 1037. https://doi.org/10.1016/j.jallcom.2025.182111

MLA:

Fritton, M., et al. "Post hot-deformation precipitation behavior of γ′ phase in VDM® alloy 780 under varying cooling rates and aging temperatures: An in situ high energy XRD study." Journal of Alloys and Compounds 1037 (2025).

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