Unambiguous Stacking Fault Analysis for Unraveling Shearing Mechanisms and Shear-Based Transformations in the L12-Ordered γ′ Phase

Karpstein N, Lenz M, Bezold A, Zehl R, Wu M, Ludwig A, Laplanche G, Neumeier S, Spiecker E (2024)

Publication Language: English

Publication Status: Published

Publication Type: Conference contribution, Original article

Publication year: 2024

Publisher: Springer Science and Business Media Deutschland GmbH

Series: Minerals, Metals and Materials Series

Pages Range: 44-52

Conference Proceedings Title: Proceedings of the 15th International Symposium on Superalloys

Event location: Champion, PA, USA

ISBN: 9783031639364

DOI: 10.1007/978-3-031-63937-1_4

Abstract

With its precipitation strengthening effect, the L1₂-ordered γ′ phase contributes substantially to the mechanical properties of superalloys; therefore, understanding the microscopic mechanisms by which it can be sheared is of key importance. A commonly used method to study these mechanisms involves high-resolution imaging in the transmission electron microscope in <110> projection which enables straightforward discrimination between intrinsic and extrinsic stacking faults as well as microtwins. However, the complex or superlattice nature of these stacking fault structures, which provides key information on their formation mechanism, is not necessarily revealed in this projection. In the present work, an experimental approach is presented to resolve this ambiguity and reliably determine the complex or superlattice nature of a stacking fault in the L1₂ structure by additionally imaging the fault in a nearby <211> projection, which is achieved by tilting the specimen by 30°. The method is demonstrated using two different examples in single-crystalline Co-base superalloys. In the first example, the approach enabled the direct experimental verification of two key aspects of the well-known Kolbe mechanism for superlattice extrinsic stacking fault formation, namely, the complex nature of the leading intrinsic stacking fault segment and the occurrence of diffusion-mediated re-ordering. In the second example, microscopic details of the shear-based transformation from the cubic L1₂-γ′ to the hexagonal D0₁₉-χ phase are revealed, accounting for additional complexities—again including a re-ordering process—arising from the superlattice ordering of both phases.

Authors with CRIS profile

Involved external institutions

Ruhr-Universität Bochum (RUB) Germany (DE)

How to cite

APA:

Karpstein, N., Lenz, M., Bezold, A., Zehl, R., Wu, M., Ludwig, A.,... Spiecker, E. (2024). Unambiguous Stacking Fault Analysis for Unraveling Shearing Mechanisms and Shear-Based Transformations in the L12-Ordered γ′ Phase. In Jonathan Cormier, Ian Edmonds, Stephane Forsik, Paraskevas Kontis, Corey O’Connell, Timothy Smith, Akane Suzuki, Sammy Tin, Jian Zhang (Eds.), Proceedings of the 15th International Symposium on Superalloys (pp. 44-52). Champion, PA, USA, US: Springer Science and Business Media Deutschland GmbH.

MLA:

Karpstein, Nicolas, et al. "Unambiguous Stacking Fault Analysis for Unraveling Shearing Mechanisms and Shear-Based Transformations in the L12-Ordered γ′ Phase." Proceedings of the 15th International Symposium on Superalloys, ISS 2024, Champion, PA, USA Ed. Jonathan Cormier, Ian Edmonds, Stephane Forsik, Paraskevas Kontis, Corey O’Connell, Timothy Smith, Akane Suzuki, Sammy Tin, Jian Zhang, Springer Science and Business Media Deutschland GmbH, 2024. 44-52.

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