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Shear bands in metallic glasses: what are they, how to find them?

  • Date: Oct 25, 2017
  • Time: 10:00 - 11:00
  • Speaker: P. Denis
  • University of Ulm, Institute of Micro and Nanomaterials, Albert-Einstein-Allee 47, D-89081 Ulm, Germany pierre.denis@uni-ulm.de
  • Location: Max-Planck-Institut für Eisenforschung GmbH
  • Room: Seminar Room 1
The plastic deformation in metallic glasses proceeds through the activation and sliding of shear bands (SBs). A better plasticity in metallic glasses can be achieved through the enhancement of SB stability and proliferation. Therefore, efforts have been made to understand the true nature of SBs in metallic glasses. However, direct measurements on SBs are limited due to the small width of a shear band (few tenths of nanometers) and the lack of resolution at the atomic scale. In this context, atom probe tomography could bring some missing information about SBs.In the first part of the talk, I present the current state of knowledge on shear bands in metallic glasses. I give information concerning the commonly accepted formation, nature and location of shear bands. In the second part of the talk, I present my own results with Pd- and Pt-based bulk metallic glasses (BMGs) samples deformed by High-Pressure Torsion. HR-TEM and DSC measurements indicate some changes in the short-range order of the samples. The importance of pre-existing SB spacing on the mechanical response during nanoindentation measurements is also presented. The influence of residual stresses on SB proliferation around indenter imprint is shown. Finally, we show the possibility of a phase separation in amorphous Au-based metallic glass thin films and Zr-based BMGs. Atom probe tomography could also be used to confirm the presence of multiple amorphous phases.
 
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