Berlin 2012 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 38: Liquid and Amorphous Metals

MM 38.3: Vortrag

Mittwoch, 28. März 2012, 15:30–15:45, H 1029

Strain localization in amorphous Cu-Zr nanowires: Molecular dynamics simulations on the influence of size, surface relaxation state and temperature — •Yvonne Ritter and Karsten Albe — Institut für Materialwissenschaft, Technische Universität Darmstadt, Petersenstr. 32, 64287

Plastic deformation in bulk metallic glasses occurs at room temperature highly localized in narrow shear bands. Recent experiments, however, suggest a transition in deformation mode, from shear banding to a more homogeneous plastic deformation, if sample dimensions reach the nanometer regime. Despite the growing number of reports on size-dependent plasticity, doubts about the intrinsic nature of this size effect persist. When it comes to mechanical testing of nanoscale specimen, experimental artifacts can change the operating deformation mechanism.

In this study, cylindrical amorphous nanowires with diameters of 5-20 nm are studied by molecular dynamics simulations under tensile load. Two different amorphous alloys, a Cu₆₄Zr₃₆ and a Cu₃₆Zr₆₄ glass, are compared. By varying the surface relaxation state, temperature and sample diameter we find from the analysis of a statistically relevant number of samples no evidence for an intrinsic size-dependent transition in deformation mode. In both alloys, the occurrence of shear bands, neck formation or homogeneous flow is solely determined by the nucleation and coalescence of shear transformation zones exhibiting a size-independent activation free energy.