Berlin 2012 – wissenschaftliches Programm

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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: Vortrag

Donnerstag, 29. März 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.