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MM: Fachverband Metall- und Materialphysik

MM 60: Nanomaterials IV - Deformation and mechanical properties

MM 60.3: Vortrag

Donnerstag, 3. April 2014, 16:15–16:30, IFW B

A comparative study of the mechanical behavior of nanocrystalline metals and bulk metallic glasses using shear compression specimen — •Christian Braun, Manuel Grewer, and Rainer Birringer — Universität des Saarlandes, FR 7.2 Experimentalphysik, Campus D2.2, 66123 Saarbrücken

Polycrystalline metals at the low end of the nanoscale with grain sizes of 10 nm or less are characterized by a grain boundary volume fraction of at least 30%. Grain boundary deformation modes similar to shear transformations in bulk metallic glasses (BMGs) may therefore play a non-negligible role in the mechanical behavior of nanocrystalline (nc) metals. In fact, a couple of similarities between this two material classes have been observed, e.g. comparable values for the shear activation volume, activation energy or Mohr-Coulomb friction coefficient. In BMGs, increasing load causes percolation of shear transformations that leads to shear band formation and concomitant strain localization followed by catastrophic failure. On the other hand, in nc metals the deformation seems to be carried by shear transformations distributed across the network of grain boundaries. Instead of catastrophic failure through shear banding, nc metals at the low end of the nanoscale even exhibit strain hardening. We will discuss in detail the similarities and dissimilarities of the deformation behavior of nc Pd90Au10 and the BMG Pd40Ni40P20 under the same loading conditions.