Probing local atomic strain of metallic glasses with nanometer resolution using TEM diffraction mapping

Research output: ThesisMaster's Thesis

190 Downloads (Pure)

Abstract

This thesis elucidates the characterization of metallic glasses (MGs) by means of scanning nanobeam electron diffraction (NBED) mapping, also known as four-dimensional scanning transmission electron microscopy (4D STEM), using precession electron diffraction (PED). An emphasis lies on the evaluation of nanodiffraction datasets through fitting of a parametric ellipse equation, which enables two-dimensional determination of local elastic strains, as well as structural and compositional characterization at the nanoscale. An insight is given into the implementation of the fitting procedure, as well as dataset acquisition and subsequent data processing steps. A study is conducted on a Cu-Zr-Al bulk-metallic-glass (BMG) alloy, to determine optimal experimental parameters and a suitable evaluation approach. The results demonstrate the potential of mapping intrinsic structural heterogeneities in metallic glasses (MGs). The method is applied to a multilayered Co-Ta-B MG thin film system, demonstrating a spatial resolution of a few nanometres for the determination of elastic strains, as well as structural and compositional characterization. The results also provide unique insight into strain distribution and structure at amorphous interfaces. Additionally, an in-situ nanomechanical testing experiment is conducted on a Cu-Zr-Al BMG bending beam, during which 4D STEM strain mapping datasets are acquired. The subsequent evaluation allows the quantification of local multiaxial elastic strain distributions, occurring at different bending loads, which indicate an evolution of the stress concentrations at the beam notch position. The unprecedented resolution with which local elastic strains, structure and composition of MGs can be characterized, enables opportunities for material optimization, such as the quantitative comparison of obtained results to simulations.
Translated title of the contributionMessung der atomaren Spannungsverteilung von metallischen Gläsern im Nanometerbereich mittels ortsaufgelöster TEM Beugung
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Eckert, Jürgen, Supervisor (internal)
Award date8 Apr 2022
Publication statusPublished - 2022

Bibliographical note

no embargo

Keywords

  • metallic glasses
  • scanning transmission electron microscopy
  • electron diffraction
  • nanodiffraction
  • data fitting

Cite this