Application of microLaue diffraction using a 3D energy-dispersive detector to study the evolution of fatigue damage in polycrystalline structural materialsy
Experimental Condensed Matter Physics
Final Report Abstract
In the framework of the research project, three materials were investigated by means of energydispersive µLaue-diffraction (EDLD) in order to analyze the microstructural changes resulting from fatigue loading. For this purpose, specific dislocation structures were induced in the materials and characterized in detail using transmission electron microscopy. The study focused on the very-highcycle-fatigue range, since under these conditions the microstructural changes are crucial for the fatigue life and the existence of a true fatigue limit. The EDLD experiments were carried out appying a special energy dispersive detector and a white X-ray beam preferentially produced in a synchrotron radiation facility. The detector applied enables a position-sensitive measurement of the diffraction energy and intensity within few minutes. Also, a software package needed to be developed, which allows for a quick and widely autonomous data collection and evaluation. It could be demonstrated that individually deformed planes can be indexed and assigned to the specific reflecting grain by means of EDLD. Especially, if plastic deformation takes place in single grains, the results form a valuable supplement of common methods which rely on transmission electron microscopy. EDLD supports not only the determination of those grains or grain areas, which are cyclically deformed, but also sheds light on the behavior of neighboring grains. This feature can be used to gain information on the barrier strength of grain boundaries. The displacement of crystal planes and the local dislocation density can also be calculated from the diffraction data without a large effort for sample preparation. However the experimental requirements of EDLD are very demanding. It was clearly shown that the diffraction patterns changes with proceeding cyclic loading and with increasing plastic strain amplitude. However, the fatigue damage state cannot be derived from a single diffraction pattern. Rather only comparative (relative) results can be obtained. Interestingly, especially for wavy-dislocation-slip-behavior materials at high plastic strain amplitudes, strongly extended X-ray streaks are formed, which can hardly be detected anymore. If a certain high strain amplitude is reached, the streaks disappear in the X-ray background noise of the detector. For this reason, the application of EDLD in the low cycle fatigue range is strongly restricted. However, it turned out that the increasing broadening of streaks and their decreasing number before fatigue failure can be used as indicator of an imminent failure. Further experiments will be carried out to support this hypothesis. Summarizing, it can be stated that the concept applied (based on EDLD) is able to provide important information with respect to the change of the dislocation density and arrangement during cyclic deformation. However, this method should be considered as a continuative and supplementary investigation technique, since (i) a TEM examination of the microstructural processes is still necessary as basis for the interpretation of the EDLD data and (ii) the correlation between damage evolution and microstructure development is rather indirect.
Publications
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Lattice tilt and subdivision of grains during crack formation in VHCF duplex stainless steel using microbeam X-ray Laue diffraction. Beitrag zur int. Tagung VHCF7, Siegener werkstoffkundliche Berichte 14 (Hrsg. M. Zimmermann und H.-J. Christ) (2017), Seventh International Conference on Very High Cycle Fatigue (Dresden), Siegen, S. 93-98
A. Abboud, B. Dönges, M. Shokr, A. Tossen, J.-S. Micha, R. Hartmann, L. Strüder, H.-J. Christ, U. Pietsch
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Influence of different loading stresses on the peak shape of X-ray rocking curves of an austenitic-ferritic duplex stainless steel during VHCF. Fatigue of Materials at Very High Number of Loading Cycles – Experimental Techniques, Mechanisms, Modeling and Fatigue Life Assessment (Hrsg. Springer Fachmedien Wiesbaden GmbH; Editor: H.-J. Christ) (2018), Springer Spektrum, Wiesbaden, S. 133-147
A. K. Hüsecken, B. Dönges, M. Söker, K. Istomin, U. Krupp, H.-J. Christ, U. Pietsch
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Untersuchungen der Ermüdungsschädigungsentwicklung in metallischen Strukturwerkstoffen mittels Laue-Beugung unter Nutzung eines 3D-energiedispersiven Detektors; Werkstoffe und Bauteile auf dem Prüfstand – Prüftechnik – Kennwertermittlung – Schadensvermeidung (Hrsg.: H.-J. Christ) (2019), Tagung Werkstoffprüfung 2019, INVENTUM GmbH, Sankt Augustin, S. 75-80
C. Leidigkeit, A. Abboud, M. Shokr, U. Pietsch, H.-J. Christ
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In situ observations of single grain behavior during plastic deformation in polycrystalline Ni using energy dispersive Laue diffraction. Materials Science and Engineering A 772 (2020), S. 138778
M. Shokr, A. Abboud, C. Kirchlechner, N. Malyar, U. Ariunbold, R. Hartmann, L. Strüder, C. Genzel, M. Klaus, U. Pietsch
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Untersuchungen der Ermüdungsschädigung in Nickel mittels µLaue-Beugung unter Nutzung eines 3D-energiedispersiven Detektors. Werkstoffe und Bauteile auf dem Prüfstand – Prüftechnik – Kennwertermittlung – Schadensvermeidung (Hrsg.: J. B. Langer und M. Wächter) (2020), Tagung Werkstoffprüfung 2020, DVM e.V., Berlin, S. 117-122
C. Leidigkeit, H.-J. Christ, M. Shokr, U. Pietsch
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Untersuchungen der Ermüdungsschädigung in Nimonic 75 mithilfe der µLaue-Röntgenbeugung unter Verwendung eines energiedispersiven Detektors. Werkstoffe und Bauteile auf dem Prüfstand (Hrsg.: S. Brockmann und U. Krupp) (2021), Tagung Werkstoffprüfung 2021, Stahlinsitut VDEh, Düsseldorf, S. 259-264
C. Leidigkeit, H.-J. Christ, M. Shokr, U. Pietsch
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VHCF damage in duplex stainless steel revealed by microbeam energy-dispersive X- ray Laue diffraction. International Journal of Fatigue 151 (2021), S. 106358
A. Abboud, A. AlHassan, B. Dönges, J. S. Micha, R. Hartmann, L. Strüder, H.-J. Christ, U. Pietsch
