Kashiwar, Ankush ; Hahn, Horst ; Kübel, Christian (2021)
In situ TEM observation of cooperative grain rotations and the Bauschinger effect in nanocrystalline palladium.
In: Nanomaterials, 11 (2)
doi: 10.3390/nano11020432
Artikel, Bibliographie
Kurzbeschreibung (Abstract)
We report on cooperative grain rotation accompanied by a strong Bauschinger effect in nanocrystalline (nc) palladium thin film. A thin film of nc Pd was subjected to cyclic loading-unloading using in situ TEM nanomechanics, and the evolving microstructural characteristics were investigated with ADF-STEM imaging and quantitative ACOM-STEM analysis. ADF-STEM imaging revealed a partially reversible rotation of nanosized grains with a strong out-of-plane component during cyclic loading-unloading experiments. Sets of neighboring grains were shown to rotate cooperatively, one after the other, with increasing/decreasing strain. ACOM-STEM in conjunction with these experiments provided information on the crystallographic orientation of the rotating grains at different strain levels. Local Nye tensor analysis showed significantly different geometrically necessary dislocation (GND) density evolution within grains in close proximity, confirming a locally heterogeneous deformation response. The GND density analysis revealed the formation of dislocation pile-ups at grain boundaries (GBs), indicating the generation of back stresses during unloading. A statistical analysis of the orientation changes of individual grains showed the rotation of most grains without global texture development, which fits to both dislocation- and GB sliding-based mechanisms. Overall, our quantitative in situ experimental approach explores the roles of these different deformation mechanisms operating in nanocrystalline metals during cyclic loading.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2021 |
| Autor(en): | Kashiwar, Ankush ; Hahn, Horst ; Kübel, Christian |
| Art des Eintrags: | Bibliographie |
| Titel: | In situ TEM observation of cooperative grain rotations and the Bauschinger effect in nanocrystalline palladium |
| Sprache: | Englisch |
| Publikationsjahr: | Februar 2021 |
| Verlag: | MDPI |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Nanomaterials |
| Jahrgang/Volume einer Zeitschrift: | 11 |
| (Heft-)Nummer: | 2 |
| DOI: | 10.3390/nano11020432 |
| Kurzbeschreibung (Abstract): | We report on cooperative grain rotation accompanied by a strong Bauschinger effect in nanocrystalline (nc) palladium thin film. A thin film of nc Pd was subjected to cyclic loading-unloading using in situ TEM nanomechanics, and the evolving microstructural characteristics were investigated with ADF-STEM imaging and quantitative ACOM-STEM analysis. ADF-STEM imaging revealed a partially reversible rotation of nanosized grains with a strong out-of-plane component during cyclic loading-unloading experiments. Sets of neighboring grains were shown to rotate cooperatively, one after the other, with increasing/decreasing strain. ACOM-STEM in conjunction with these experiments provided information on the crystallographic orientation of the rotating grains at different strain levels. Local Nye tensor analysis showed significantly different geometrically necessary dislocation (GND) density evolution within grains in close proximity, confirming a locally heterogeneous deformation response. The GND density analysis revealed the formation of dislocation pile-ups at grain boundaries (GBs), indicating the generation of back stresses during unloading. A statistical analysis of the orientation changes of individual grains showed the rotation of most grains without global texture development, which fits to both dislocation- and GB sliding-based mechanisms. Overall, our quantitative in situ experimental approach explores the roles of these different deformation mechanisms operating in nanocrystalline metals during cyclic loading. |
| Freie Schlagworte: | nanocrystalline metals, nanomechanical behavior, plasticity, thin films, Bauschinger effect, deformation mechanisms, grain rotation, in situ transmission electron microscopy (TEM), automated crystal orientation mapping in STEM (ACOM-STEM) |
| Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > In-Situ Elektronenmikroskopie |
| Hinterlegungsdatum: | 12 Jun 2024 08:06 |
| Letzte Änderung: | 12 Jun 2024 08:06 |
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