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Effect of Sc, Sr Elements on Eutectic Mg2Si Modification and Castability of Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe Casting Alloy

주조용 Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe 합금의 공정 Mg2Si 개량과 주조특성에 미치는 Sc, Sr 첨가원소의 영향

Kim, Heon-Joo
김헌주

  • Received : 2015.09.07
  • Accepted : 2015.10.16
  • Published : 2015.12.31

Abstract

The effects of Sc and Sr elements on the modification of the eutectic $Mg_2Si$ phase and the castability were investigated in the Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurements of the cooling curve and microstructure observations were performed to analyze the additional effects of Sc and Sr minor elements during the solidification process. A prominent effect found on the modification of the eutectic $Mg_2Si$ phase with additions of the Sr and Sc elements. Here, a fine eutectic $Mg_2Si$ phase and a decrease in the growth temperature of the eutectic $Mg_2Si$ phase were evident with an addition of Sc element up to 0.2 wt%. The growth temperature of the eutectic $Mg_2Si$ phase decreased and the effect on the modification of the eutectic $Mg_2Si$ phase increased with the addition of Sr element up to 0.02 wt%. The addition of 0.02wt%Sr had the strongest effect on the modification of the eutectic $Mg_2Si$ phase, and the resulting microstructure of the eutectic $Mg_2Si$ phase was found to have a fibrous morphology with a decreased aspect ratio and an increased modification ratio. Fluidity and shrinkage tests were conducted to evaluate the castability of the alloy. The addition of 0.02wt%Sr effectively increased the fluidity of the alloy, while an addition of Sc did not show any effect compared to when nothing was added. The maximum filling length was recorded for 0.01wt%TiB-0.02wt%Sr owing to the effect of the fine ${\alpha}$-Al grains. The macro-shrinkage ratio decreased, while the micro-shrinkage ratio increased with the addition of various eutectic modifiers. The highest ratio of micro-shrinkage was recorded for the 0.02wt%Sr condition. However, the total shrinkage ratio was nearly identical regardless of the amounts added in this study.

Keywords

Eutectic $Mg_2Si$ modification;Fluidity test;Shrinkage test;Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy

References

  1. Kim JM, Seong KD, Jun JH, Kim KT and Jung WJ, J. Korea Foundry Society, "Variation of fluidity and mechanical properties of Al-Mg alloys with the addition of Si, Mn and Zn", 24 (2004) 138-144.
  2. K. Al-Helal, I.C. Stone and Z. Fan, Transactions of the Indian Institute of Metals, "Simultaneous Primary Si Refinement and Eutectic Modification in Hypereutectic AlSi Alloys", 65 (2012) 663-667. https://doi.org/10.1007/s12666-012-0171-4
  3. B.N.Sarada, P.L. Srinivasamurthy and Swetha, International Journal of Innovative Research in Science, Engineering and Technology, "Microstructural Characteristics of Sr And Na Modified Al-Mg-Si Alloy", 2 (2013) 3975-3983.
  4. Kim MH and Lee JT, J. Korea Foundry Society, "The Effects of Sc on the Microstructure of Hypoeutectic Al-Si Alloys", 24 (2004) 145-152.
  5. John E. Gruzleski and Bernard M. Closset, The Treatment of Liquid Aluminum-silicon Alloys, American Foundrymen's Society, Illinois (1990) 39-41.
  6. S. G. Shabestari and S. Ghodrat, Materials Sci. and Eng. A, "Assesment of modification and formation of intermetallic compounds in aluminum alloy using thermal analysis", 467 (2007) 150-158. https://doi.org/10.1016/j.msea.2007.05.022
  7. K. R. Ravi, R. M. Pillai, K. R. Amaranathan, B. C. Pai and M. Chakraborty, Journal of Alloys and compounds, "Fluidity of aluminum alloys and composites", 456 (2008) 201-210. https://doi.org/10.1016/j.jallcom.2007.02.038
  8. Dang, J.Z., Huang, Y.F. and Cheng, J, Transactions of Nonferrous Metals Society of China, "Effect of Sc and Zr on microstructures and mechanical properties of as-cast Al-Mg- Si-Mn alloys", 19 (2009) 540-544. https://doi.org/10.1016/S1003-6326(08)60309-X
  9. D. Emadi, J.E. Gruzleski, and J.M. Togurt, Metallugical Transactions B, "The Effect of Na and Sr Modification on Surface Tension and Volumetric Shrinkage A356 Alloy and Their Influence on Porosity of Formation", 24B (1993) 1055-1063.
  10. M. C. Flemings, Metallurgical Transactions, "Solidification Processing", 5 (1974) 2121-2134. https://doi.org/10.1007/BF02643923
  11. G. Lang Ranshofen, Aluminium, "Giesseigenschaften und Oberflächenspannung von Aluminumund binren Aluminiumlegierungen", 48 (1972) 664-672.
  12. A. K. Dahle, P. A. Tondel, C. J. Raradies and L. Arnberg, Met. and Mat. Trans., "A Effect of Grain Refinement in the Fluidity of Two commercial Al-Si Foundry Alloys", 27A (1996) 2305-2313.
  13. S. D. Mcdonald, A. K. Dahle, J. A. Taylor and D. H. StJohn, Met. and Mat. Trans. B, "Modification-Related Porosity Formation in Hypoeutectic Aluminum- Silicon Alloys", 35B (2004) 1097-1106.
  14. John E. Gruzleski and Bernard M. Closset, The Treatment of Liquid Aluminum-silicon Alloys, American Foundrymen's Society, Illinois (1990) 57-73.
  15. R. Cook, Modification of aluminium - silicon foundry alloys, London & Scandinavian metallurgical Co. Limited, London (1998) 12-14.