Abstract
In the present work, six specimens of hypo-eutectic Al-3Si-0.45Mg-0.45Cu-0.2Sc-0.2Zr cast alloys were made by a traditional casting process. The changes in microstructure and mechanical properties of the alloys at different Sr concentrations were studied using metallographic observation, tensile strength testing, and SEM analysis. The results show that, when the Sr content increased, the grain morphology underwent significant changes, from dendrites to isometric grains, and the Si phase in the eutectic region was greatly transformed and its grain sizes became smaller. However, over-modification, in excessive Sr content samples affected the mechanical performance overall. The best morphology with regards grain size and the silicon phase appeared in 0.06 % and 0.08 % Sr concentration specimens. The mechanical properties of the alloy were maximised and then decreased with increasing Sr concentration. The tensile test results indicated that the alloy with the best mechanical properties was that at 0.08 % Sr addition as evinced by its optimal morphological parameters.
Kurzfassung
Im vorliegenden Beitrag wurden durch ein traditionelles Gießverfahren sechs Proben aus hypoeutektischen Al-3Si-0.45Mg-0.45Cu-0.2Sc-0.2Zr-Gusslegierungen hergestellt. Die Veränderungen von Mikrostruktur und mechanischen Eigenschaften der Legierungen bei unterschiedlichen Sr-Konzentrationen wurden mit Hilfe von metallographischen Beobachtungen, Zugfestigkeitstests und REM-Analyse untersucht. Die Ergebnisse zeigen, dass es bei steigendem Sr-Gehalt zu erheblichen Veränderungen der Kornmorphologie kommt – von Dendriten zu isometrischen Körnern – und sich die Si-Phase in der eutektischen Region stark verändert und ihre Korngrößen abnehmen. Durch Modifizierung beeinträchtigen die Proben mit hohem Sr-Gehalt die allgemeine mechanische Leistung. Die beste Morphologie hinsichtlich Korngröße und Siliziumphase tritt bei Proben mit Konzentrationen von 0,06 % und 0,08 % Sr auf. Die mechanischen Eigenschaften der Legierung wurden maximiert und nahmen dann mit steigender Sr-Konzentration ab. Die Ergebnisse der Zugfestigkeitstests deuten darauf hin, dass die Legierung mit einem Gehalt von 0,08 % Sr die besten mechanischen Eigenschaften zeigt. Dies wird durch die optimalen morphologischen Parameter belegt.
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