Plasmon energy losses in shear bands of metallic glass

Maximilian Grove; Martin Peterlechner; Harald Rösner; Robert Imlau; Alessio Zaccone; Gerhard Wilde

doi:10.1016/j.ultramic.2021.113220

Plasmon energy losses in shear bands of metallic glass

Ultramicroscopy. 2021 Apr:223:113220. doi: 10.1016/j.ultramic.2021.113220. Epub 2021 Feb 9.

Authors

Maximilian Grove¹, Martin Peterlechner¹, Harald Rösner², Robert Imlau³, Alessio Zaccone⁴, Gerhard Wilde¹

Affiliations

¹ Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany.
² Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany. Electronic address: rosner@uni-muenster.de.
³ Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, The Netherlands.
⁴ Department of Physics "A. Pontremoli", University of Milan, via Celoria 16, 20133 Milano, Italy; Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, UK; Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 9HE Cambridge, UK.

PMID: 33607307
DOI: 10.1016/j.ultramic.2021.113220

Abstract

Shear bands resulting from plastic deformation in cold-rolled Al₈₈Y₇Fe₅ metallic glass were observed to display alternating density changes along their propagation direction. Electron-energy loss spectroscopy (EELS) was used to investigate the volume plasmon energy losses in and around shear bands. Energy shifts of the peak centre and changes in the peak width (FWHM) reflecting the damping were precisely determined within an accuracy of a few meV using an open source python module (Hyperspy) to fit the shapes of the plasmon and zero-loss peaks with Lorentzian functions. The maximum bulk plasmon energy shifts were calculated for the bright and dark shear band segments relative to the matrix to be about 38 and 14 meV, respectively. The damping was observed to be larger for the denser regions. The analysis presented here suggests that the changes in the plasmons are caused by two contributions: (i) Variable damping in the shear band segments due to changes in the medium-range order (MRO). This affects the static structure factor S(k), which, in turn, leads to either reduced or increased damping according to the Ziman-Baym formula. (ii) The ionic density and the effective electron mass appearing in the zero-momentum plasmon frequency formula E_p(q=0) are coupled and give rise to small variations in the plasmon energy. The model predicts plasmon energy shifts in the order of meV.

Keywords: Deformation; Electron energy loss spectroscopy; Metallic glass; Shear band; Volume plasmon.