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Double minimum creep of single crystal Ni-base superalloys

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    0464792 - ÚFM 2017 RIV GB eng J - Journal Article
    WU, X. - Wollgramm, P. - Somsen, C. - Dlouhý, Antonín - Kostka, A. - Eggeler, G.
    Double minimum creep of single crystal Ni-base superalloys.
    Acta Materialia. Roč. 112, JUN (2016), s. 242-260. ISSN 1359-6454
    R&D Projects: GA ČR(CZ) GA14-22834S
    Institutional support: RVO:68081723
    Keywords : Single crystal Ni-base superalloys * Primary creep * Transmission electron microscopy * Dislocations * Stacking faults
    Subject RIV: JG - Metallurgy
    Impact factor: 5.301, year: 2016

    Low temperature (750°C) and high stress (800 MPa) creep curves of single crystal superalloy ERBO/1 tensile specimens loaded in the (001) direction show two creep rate minima. Strain rates decrease towards a first sharp local creep rate minimum at 0.1% strain (reached after 30 min). Then deformation rates increase and reach an intermediate maximum at 1% (reached after 1.5 h). Subsequently, strain rates decrease towards a global minimum at 5% (260 h), before tertiary creep (not considered in the present work) leads to final rupture. We combine high resolution miniature creep testing with diffraction contrast transmission electron microscopy and identify elementary processes which govern this double-minimum type of creep behavior. We provide new quantitative information on the evolution of microstructure during low temperature and high stress creep, focusing on γ-channel dislocation activity and stacking fault shear of the γ′-phase. We discuss our results in the light of previous work published in the literature and highlight areas in need of further work.
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