Dresden 2009 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 4: Mechanical Properties II
MM 4.3: Vortrag
Montag, 23. März 2009, 12:15–12:30, IFW B
In-situ SEM micropillar compression of Zr-based bulk metallic glasses with different free volume content — •Alban Dubach1,2, Johann Michler2, Upadrasta Ramamurty3, and Jörg F. Löffler1 — 1Laboratory of Metal Physics and Technology, ETH Zurich, Wolfgang-Pauli-Str. 10, 8093 Zürich, Switzerland — 2EMPA Materials Science and Technology, Feuerwerkerstrasse 39, 3602 Thun, Switzerland — 3Department of Materials Engineering, Indian Institute of Science, Bangalore-560012, India
In contrast to crystalline metals, which exhibit dislocation-mediated deformation, bulk metallic glasses (BMGs) usually exhibit high yield strength and a plastic deformation which is triggered by free volume. Under an applied stress, clusters of atoms with high free volume (i.e. "shear transformation zones", STZs) accommodate shear strains locally. At room temperature these STZs coalesce along planes of maximum shear stress, leading to a deformation which is spatially and temporally restricted within narrow shear bands and therefore difficult to assess experimentally. In this study the uniaxial compression of micrometer-sized pillars has been investigated in-situ inside a scanning electron microscope. The micropillars, having diameters between 0.3 and 3 µm, were fabricated by focused-ion beam milling of a Zr-based BMG in three different conditions: as-cast, structurally-relaxed and shot-peened. Effects of different free volume content, sample size and applied strain rate have been analyzed. Shear band formation and stable propagation is observed to be the plastic deformation mode, with no difference in yield strength according to either size or condition.