Diffraction d'électrons rétrodiffusés

Résumé

thumb|Cliché de diffraction obtenu par EBSD thumb|Cliché EBSD du silicium monocristallin, obtenu à 20 kV avec un canon à émission de champ right|thumb|Principe de l’EBSD La diffraction d'électrons rétrodiffusés (en anglais electron backscatter diffraction ou EBSD, ou encore backscatter Kikuchi diffraction ou BKD) est une technique cristallographique microstructurale permettant de mesurer l'orientation cristallographique de nombreux matériaux, qui peut être utilisée pour déterminer la texture ou l'orientation préférentielle de n'importe quel matériau monocristallin ou polycristallin. L'EBSD peut être utilisée pour indexer et identifier les sept systèmes cristallins, et est appliquée à la cartographie d'orientation cristalline, l'étude des défauts, l'identification des phases, l'étude des joints de grains et de la morphologie, l'examen des hétérogénéités locales, l'identification des matériaux, la cartographie des déformations, et à l'aide de techniques complémentaires, l'identification

Source officielle

https://fr.wikipedia.org/wiki/Diffraction_d'%C3%A9lectrons_r%C3%A9trodiffus%C3%A9s

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Hot deformation of a Fe-Mn-Al-C steel susceptible of κ-carbide precipitation

Roland Logé, Oscar Zambrano Zambrano

The mechanical properties of Fe-Mn-Al-C steel are significantly enhanced after κ-carbide precipitation via aging; however, most aging treatments are energy demanding because they require relatively high temperatures and extended holding times. This research determined that the precipitation of these carbides can also occur within a few seconds of thermomechanical treatments (TMTs). This behaviour has not been reported post-TMTs for this steel group. Hot compression tests were performed on Fe-21Mn-11Al-1.5C-2Si wt% specimens at test temperatures ranging from 900 °C to 1150 °C and strain rates varying from 0.01 s−1 to 1 s−1. The effects of strain rate and test temperature on dynamic recrystallization behaviour were evaluated. The microstructures were characterized by scanning electron microscope and electron backscatter diffraction. Hardness tests were performed before and after applying processes studied i.e., TMT and aging treatment to determine the change in hardness induced. Particularly, nanoindentation tests were also used to collect indirect evidence about the deformation mechanisms. The load-displacement curves P-h and (P/h)-h showed the occurrence of several popins and slope changes related to the nucleation of dislocations and strain-induced phase transformations. The occurrence of these phenomena is discussed.

Elsevier Science Sa2017

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Microstructural Evolution Study of Fe-Mn-Al-C Steels Through Variable Thermomechanical Treatments

Roland Logé, Oscar Zambrano Zambrano

The microstructural evolution of the two austenitic alloys Fe-20Mn-3Al-0.7C wt pct and Fe-20Mn-6Al-0.7C wt pct when different thermal and thermomechanical treatments are performed has been studied. To this end, a generic industrial die of 100 ton capacity and a Gleeble 3800 simulator were selected to perform the thermomechanical treatments. A solubilization treatment was carried out at 1100 degrees C for 4 days for the two alloys in as cast state. In addition, the specimens deformed with the industrial die underwent a solubilization treatment at 1100 degrees C for 4 hours. Microstructural characterizations were performed by X-ray diffraction, transmission Mossbauer spectrometry, and electron backscatter diffraction. The results showed both the formation of different austenites rich and poor in solute atoms, as well as different microstructures, as a function of the treatments performed, which affected the resulting dynamically recrystallized microstructures. Notably, it was observed that it is possible to explain and relate the evolution of the microstructure to the hyperfine parameters resulting from fitting the Mossbauer spectra. In particular, the relationship between the degree of dynamic recrystallization and the evolution of an ordered austenitic structure is discussed.

SPRINGER2021

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Computational and experimental demonstration of dendritic crystal growth direction and the morphologic diversity of the resulting dendritic structures are discussed. The primary dendrite growth directions can vary continuously between different crystallographic directions as a function of the composition-dependent anisotropy parameters. The dendritic microstructure of chemically etched and electropolished longitudinal sections of solidified alloys was analyzed using scanning electron microscopy and electron back-scattered diffraction (EBSD) orientation measurements. The experimental results shows the change of dendritic growth direction of compositions as a function of anisotropy in the phase-field simulation. The similarities between the computational and the experimental results strongly supports the hypothesis that the change of anisotropy parameters with the composition is the underlying mechanism of the damage of growth direction observed experimentally.

2008

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