Influence of modifying mixtures on Si crystal formation in Al-7%Si alloy

Anna Zykova, Lyudmila Kazantseva, Natalya Popova, Alexander Vorozhtsov, Irina Kurzina

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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 Na3 AlF6 + K2 ZrF6 + TiO2 + ZrO2; (2) K2 ZrF6; 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.

Original languageEnglish
Article number98
JournalMetals
Volume8
Issue number2
DOIs
Publication statusPublished - 1 Feb 2018

Keywords

  • Al-7%Si alloy
  • Fine structure
  • Modification
  • Phase composition
  • Ultrafine powders

ASJC Scopus subject areas

  • Materials Science(all)

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    Zykova, A., Kazantseva, L., Popova, N., Vorozhtsov, A., & Kurzina, I. (2018). Influence of modifying mixtures on Si crystal formation in Al-7%Si alloy. Metals, 8(2), [98]. https://doi.org/10.3390/met8020098