Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 20: Topical Session Bulk Nanostrucured Materials IV - Microstructure and Characterization II
MM 20.2: Vortrag
Dienstag, 27. März 2012, 10:45–11:00, H 0107
Quantitative grain size and twin density analysis by TEM-OIM measurements for tensile testing of nanocrystalline Pd — •Aaron Kobler1,2, Anna Castrup1,2, Christian Kübel1, and Horst Hahn1,2 — 1Institute of Nanotechnology (INT/KIT), Eggenstein, Germany — 2Joint Research Laboratory Nanomaterials (KIT and TUD), Darmstadt, Germany
To study the deformation mechanisms in nanocrystalline (nc) Pd, we performed tensile tests on magnetron sputtered thin films in combination with orientation imaging (OIM) analysis in a TEM. TEM-OIM is a new technique that fills the gap of EBSD measurements for grain sizes below 30-50 nm. We have implemented the OIM (NanoMegas) on a FEI Tecnai F20 in micro-probe (up) STEM mode, that allows us to acquire (fast) STEM reference images. Once an OIM map is acquired, the grain size and twin density is evaluated using Mtex. The main advantage of this approach is a much better identification of grains and sub-grains and the detection of all twin boundaries within the area of interest. The thin films were magnetron sputtered onto Kapton films to avoid strain localization using conditions previously identified to minimize growth induced residual stress. Subsequently, the films were individually deformed in tension up to 0%, 2%, 3,5%, 5% and 10% and prepared for TEM imaging. Our evaluation based on the BF/DF-TEM and OIM reveals qualitatively similar results and show that the grain size and the twin density both increase continuously with increasing strain. However, the absolute twin density observed by OIM is significantly higher compared to DF-TEM as almost all twins are detected.