The effect of holding time after Sr addition on microstructural and mechanical properties of A356 alloy

The spheroidization of the silicon eutectic phase in aluminum is an important parameter for casting and significantly influences the material properties. Sr has been used for a long time for eutectic modification in aluminum and many researches have been made on this subject. In this study, the effect of holding time after Sr addition on the mechanical properties and eutectic phase modification of the aluminum were investigated. 200 ppm Sr was chosen as the amount of Sr and the holding times were chosen as 20, 40 and 80 minutes. Tensile test was performed for the determination of mechanical properties and ultimate tensile strength and percentage of elongation values were measured. In order to quantify eutectic modification, the length / width (aspect ratio) ratios of eutectic silicon particles were measured. In addition, Bifilm Index of the molten metal was determined with the reduced pressure test (RPT). With the increase in the holding time, an increase in the aspect ratio and in the Bifilm Index was measured. It has been observed that the tensile strength and elongation values have decreased as the holding time has increased.

___

  • Rzadkosz S, Zych J, Pıękoś M, Kozana J, Garbacz-Klempka A. “influence of refining treatments on the properties of Al-Si alloys”. Metalurgija, 54(1), 35-38, 2015.
  • Campbell J. Complete Casting Handbook: Metal Casting Processes. 1st ed. Oxford, UK, Elsevier Ltd, 2011.
  • Chirita G, Stefanescu I, Soares D, Silva FS. “Influence of vibration on the solidification behaviour and tensile properties of an Al-18wt%Si alloy”. Materials & Design, 30(5), 1575-1580, 2009.
  • Bozchaloei GE, Varahram N, Davami P, Kim SK. “Effect of oxide bifilms on the mechanical properties of cast Al-7Si-0.3Mg alloy and the roll of runner height after filter on their formation". Materials Science and Engineering A, 548, 99-105, 2012.
  • Raiszadeh R, Griffiths WD. “The behaviour of double oxide film defects in liquid al alloys under atmospheric and reduced pressures". Journal of Alloys and Compounds, 491(1-2), 575-580, 2010.
  • Zamani M, Seifeddine S. “Determination of pptimum Sr level for eutectic si modification in Al-Si cast alloys using thermal analysis and tensile properties”. International Journal of Metalcasting, 10(4), 457-465, 2016.
  • Xu C, Wang F, Mudassar H, Wang C, Hanada S, Xiao W, Ma C. “Effect of Sc and Sr on the eutectic Si morphology and tensile properties of Al-Si-Mg alloy’’. Journal of Materials Engineering and Performance, 26(4), 1605-1613, 2017.
  • Samuel AM, Garza-Elizondo GH, Doty HW, Samuel FH. “Role of modification and melt thermal treatment processes on the microstructure and tensile properties of Al-Si alloys’’. Materials & Design, 80, 99-108, 2015.
  • Uludag M, Cetin R, Dispinar D, Tiryakioglu M. “Characterization of the effect of melt treatments on melt quality in Al-7wt%Si-Mg alloys”. Metals, 157(7), 1-16, 2017.
  • Zhang J H, Xing SM, Han QY, Guo Q, Wang RF. “Effect of Sr additive amount and holding time on microstructure of A390 aluminum alloy”. 4th AMMSE, Tianjin, China, 22-24 September, 2017.
  • Derin S, Aybarç U, Birol Y. “Optimization of strontium addition for the modification of AlSi7Mg0.3 alloy”. 18th International Metallurgy and Material Congress, Istanbul, Turkey, 29 September-01 October 2016.
  • Dispinar D, Campbell J. “Use of bifilm ındex as an assessment of liquid metal quality”. International Journal of Cast Metals Research, 19(1), 5-17, 2013.
  • Dispinar D, Campbell J. “Porosity, hydrogen and bifilm content in al alloy castings”. Materials Science and Engineering A, 528(10-11), 3860-3865, 2011.
  • Miresmaeili SM. “Effect of Strontium on the oxidation behavior of liquid Al-7Si alloys”. Oxidation of Metals, 71(1-2), 107-123, 2009.
  • Dispinar D, Akhtar S, Nordmark A, Di Sabatino M, Arnberg L. “Degassing, hydrogen and porosity phenomena in A356”. Materials Science and Engineering A, 527(16-17), 3719-3725, 2010.