Tension/Compression asymmetry of a creep deformed single crystal Co-base superalloy

Journal article
(Original article)


Publication Details

Author(s): Lenz M, Eggeler Y, Müller J, Zenk C, Volz N, Wollgramm P, Eggeler G, Neumeier S, Göken M, Spiecker E
Journal: Acta Materialia
Publication year: 2018
ISSN: 1359-6454
Language: English


Abstract

The creep behavior of a multinary single crystal Co-base superalloy has
been compared for uniaxial tension and compression of 400 MPa applied
along [001] at 850 °C. Creep under tensile stress proceeds two times
faster than creep under compression. A detailed TEM study shows that
already after ∼ 0.3 % creep strain planar faults are formed in both
samples. While extended a/2<112> ribbons with SISF loops embedded
in ABPs are observed in tension, extrinsic SFs are revealed in
compression. At ∼ 5 % creep strain SISFs confined to the γ' phase
dominate in tension, whereas extrinsic SFs and microtwins extending
across both phases are the prevalent planar faults in compression. In
addition, dense networks of regular a/2<101> matrix dislocations
develop at the γ/γ' interfaces in both loading scenarios. In tensile
creep and early compressive creep the direct contribution of planar
faults to plastic deformation is minor and does not exceed 10 % of the
measured plastic strain. In contrast, thickening of microtwins appears
to become an efficient deformation channel in the later stages of
compressive creep. A pronounced asymmetry regarding the rafting kinetics
is observed as well resulting in a P-type rafted and topologically
inverted microstructure after ∼ 5 % creep in tension while hardly any
rafting has occurred under compression. The pronounced rafting and
related recovery processes are likely responsible for the inferior creep
behavior in tension. Finally, two novel diffusion-assisted degradation
mechanisms related to microtwins are shown to be active: an expansion of
the γ phase into γ' precipitates along microtwins and the formation of γ
phase nuclei at planar fault intersections inside γ'. Both phenomena
are hypothesized to be triggered by segregation of γ-formers like Co and
Cr to twin boundaries.


FAU Authors / FAU Editors

Eggeler, Yolita
Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)
Göken, Mathias Prof. Dr.
Lehrstuhl für Werkstoffwissenschaften (Allgemeine Werkstoffeigenschaften)
Lenz, Malte
Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)
Müller, Julian Dr.-Ing.
Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)
Neumeier, Steffen Dr.-Ing.
Lehrstuhl für Werkstoffwissenschaften (Allgemeine Werkstoffeigenschaften)
Spiecker, Erdmann Prof. Dr.
Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)
Volz, Nicklas
Lehrstuhl für Werkstoffwissenschaften (Allgemeine Werkstoffeigenschaften)
Zenk, Christopher
Lehrstuhl für Werkstoffwissenschaften (Allgemeine Werkstoffeigenschaften)


Additional Organisation
Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)
Interdisziplinäres Zentrum, Center for Nanoanalysis and Electron Microscopy (CENEM)


External institutions with authors

Ruhr-Universität Bochum (RUB)


How to cite

APA:
Lenz, M., Eggeler, Y., Müller, J., Zenk, C., Volz, N., Wollgramm, P.,... Spiecker, E. (2018). Tension/Compression asymmetry of a creep deformed single crystal Co-base superalloy. Acta Materialia. https://dx.doi.org/10.1016/j.actamat.2018.12.053

MLA:
Lenz, Malte, et al. "Tension/Compression asymmetry of a creep deformed single crystal Co-base superalloy." Acta Materialia (2018).

BibTeX: 

Last updated on 2019-27-05 at 16:46