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Characterization of Ca Precipitation in Al-Mg Alloys Containing a Trace of Ca During Homogenization

  • Seong-Ho Ha (Korea Institute of Industrial Technology (KITECH)) ;
  • Young-Chul Shin (Korea Institute of Industrial Technology (KITECH)) ;
  • Bong-Hwan Kim (Korea Institute of Industrial Technology (KITECH)) ;
  • Young-Ok Yoon (Korea Institute of Industrial Technology (KITECH)) ;
  • Hyun-Kyu Lim (Korea Institute of Industrial Technology (KITECH)) ;
  • Sung-Hwan Lim (Kangwon National University, Department of Advanced Materials Science and Engineering) ;
  • Shae K. Kim (Korea Institute of Industrial Technology (KITECH))
  • Published : 20210000

Abstract

In this study, precipitation of Ca in Al-Mg alloys containing a trace of Ca during homogenization was investigated using a transmission electron microscope (TEM) and calculated phase diagrams. TEM result indicated that the Ca-based particles found in the examined sample are Ca7Mg7.5Si14. From the calculation of Scheil-Gulliver cooling, it was found that the Ca was formed as Al4Ca and C36 laves phases with Mg2Si and Al13Fe4 from other impurities phase during solidification. No Ca-Mg-Si ternary phase existed at the homogenization temperature in the calculated phase diagram. From the phase diagram of Al-Al4Ca-Mg2Si three-phase isothermal at 490℃, it was shown that Ca7Mg6Si14 phase co-exists with Al, Mg2Si and Al4Ca in the largest region and with only Al and Mg2Si in Al4Ca-poor regions. It was thought that the Ca7Mg6Si14 ternary phase was formed by the interaction between Mg2Si and Al4Ca considering that the segregation can occur throughout the entire microstructures.

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