Berlin 2012 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 55: Topical Session Modern Atom Probe Tomography V - Steels, Alloys and Structural Materials
MM 55.5: Talk
Thursday, March 29, 2012, 16:45–17:00, H 0107
Sr distribution in modified hypoeutectic Al-10Si alloy — •Melanie Timpel1, Nelia Wanderka1, Ralf Schlesiger2, Tomokazu Yamamoto3, Nikolai Lazarev4, Dieter Isheim5, Guido Schmitz2, Syo Matsumura3, and John Banhart1 — 1Helmholtz-Zentrum Berlin, Berlin, GER — 2Institut für Materialphysik, Westf. Wilhelms-Universität, Münster, GER — 3Kyushu University, Fukuoka, JPN — 4Kharkov Institute of Physics and Technology, Kharkov, UKR — 5Dep. of Materials Science and Engineering, Northwestern University, Evanston, USA
Small additions of Sr (≥ 200 ppm) to Al-10Si alloy drastically change the morphology of eutectic Si from large plate-like to fine fibrous (‘chemical modification’). To understand the mechanisms of modified Si growth the local distribution of Sr in eutectic Si phase has to be clarified. In this study, three-dimensional atom probe tomography and high resolution transmission electron microscopy were applied to locate Sr within the eutectic Si phase. The results of combined investigations indicate local enrichment of Sr (4 at.%) in combination with Al at specific sites of the faceted Si crystal. Linear SrAlSi segregations with tube-like morphology and average width of 4 nm were found at the origin of Si {111} twins, whereas planar SrAlSi segregations with 8×4 nm2 and length up to 220 nm were found at internal boundaries of eutectic Si. Here we show our results and discuss them with respect to previously postulated modification mechanisms.