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Influence of Modifying Mixtures on Si Crystal Formation in Al-7%Si Alloy

1
School of Core Engineering Education, National Research Tomsk Polytechnic University, 634050 Tomsk, Russian
2
Chemical Faculty and Laboratory of High-Energy and Special Materials, National Research Tomsk State University, 634050 Tomsk, Russian
3
Department of Physics, Tomsk State University of Architecture and Building, 634003 Tomsk, Russian
*
Author to whom correspondence should be addressed.
Metals 2018, 8(2), 98; https://doi.org/10.3390/met8020098
Received: 8 December 2017 / Revised: 17 January 2018 / Accepted: 25 January 2018 / Published: 30 January 2018
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Abstract

Using scanning and transmission electron microscopy, we studied silicon particles formed during the solidification of Al-7%Si alloy when different modifying mixtures were introduced into the melt: (1) a mixture of ultrafine powders Na3AlF6 + K2ZrF6 + TiO2 + ZrO2; (2) K2ZrF6; and (3) the flux Arsal. By differential scanning calorimetry, it was established that modifying mixtures significantly influenced the temperature of the solidification processes. The formation of two types of Si crystals was established. The first type of Si crystals precipitated during the solidification of the eutectic mixture (α-Al + Si) in the form of needles or plates. The second type of Si crystals was segregated from eutectic Al-phases or segregated from the solid phase α-Al upon cooling in the solid state. The introduction of modifiers led to a shift in solidification temperatures. When fluoride salts were used, there was an increase in the temperature of eutectic solidification. Silicon crystals were large (up to 10 µm), with a local excess of aluminum concentration. View Full-Text
Keywords: Al-7%Si alloy; modification; ultrafine powders; fine structure; phase composition Al-7%Si alloy; modification; ultrafine powders; fine structure; phase composition
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Zykova, A.; Kazantseva, L.; Popova, N.; Vorozhtsov, A.; Kurzina, I. Influence of Modifying Mixtures on Si Crystal Formation in Al-7%Si Alloy. Metals 2018, 8, 98.

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