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Transmission electron microscopy study of the microstructural evolution during high-temperature and low-stress (011) \(\left[{01\bar 1} \right]\) shear creep deformation of the superalloy single crystal LEK 94

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Abstract

The present work describes the shear creep behavior of the superalloy LEK 94 at temperatures between 980 and 1050 °C and shear stresses between 50 and 140 MPa for loading on the macroscopic crystallographic shear system (MCSS) (011)\(\left[{01\bar 1} \right]\). The strain rate versus strain curves show short primary and extended secondary creep regimes. We find an apparent activation energy for creep of Qapp = 466 kJ/mol and a Norton-law stress exponent of n = 6. With scanning transmission electron microscopy, we characterize three material states that differ in temperature, applied stress, and accumulated strain/time. Rafting develops perpendicular to the maximum principal stress direction, γ channels fill with dislocations, superdislocations cut γ′ particles, and dislocation networks form at γ/γ′ interfaces. Our findings are in agreement with previous results for high-temperature and low-stress [001] and [110] tensile creep testing, and for shear creep testing of the superalloys CMSX-4 and CMSX-6 on the MCSSs (111)\(\left[{01\bar 1} \right]\) and (001)[100]. The parameters that characterize the evolving γ/γ′ microstructure and the evolving dislocation substructures depend on creep temperature, stress, strain, and time.

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ACKNOWLEDGMENTS

The authors dedicate this work to Haël Mughrabi on the occasion of his 80th birthday. LAJ acknowledges funding by the German Research Foundation (DFG) through the research grant AG 191/1-1 and by the Adolf Martens Fellowship Programme of the BAM Berlin. GE acknowledges funding by the DFG through projects A1 and A2 of the collaborative research center SFB/TR 103.

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  1. This author contributed equally to this work.

Authors and Affiliations

  1. Abteilung für Werkstofftechnik, Bundesanstalt für Materialforschung und -prüfung, Berlin, 12205, Germany

    Leonardo Agudo Jácome

  2. Institut für Werkstoffe, Lehrstuhl Werkstoffwissenschaft, Ruhr-Universität Bochum, Bochum, 44801, Germany

    Gülcan Göbenli & Gunther Eggeler

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  1. Leonardo Agudo Jácome
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Correspondence to Leonardo Agudo Jácome.

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This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs.org/editor-manuscripts/.

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Agudo Jácome, L., Göbenli, G. & Eggeler, G. Transmission electron microscopy study of the microstructural evolution during high-temperature and low-stress (011) \(\left[{01\bar 1} \right]\) shear creep deformation of the superalloy single crystal LEK 94. Journal of Materials Research 32, 4491–4502 (2017). https://doi.org/10.1557/jmr.2017.336

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