Structural Characterization and Precipitation in AlMg$_{5}$Si$_{2}$Mn Alloy

V. V. Boyko$^{1}$, T. Link$^{1}$, K. V. Mykhalenkov$^{2}$

$^{1}$Technical University Berlin, Institute for Materials Science and Technology, Sekr. BH 18, Ernst-Reuter-Platz 1, D-10587 Berlin, Germany
$^{2}$National Technical University of Ukraine ‘KPI’, 37 Peremohy Ave., 03056 Kyiv, Ukraine

Received: 25.05.2014. Download: PDF

The as-cast structure of permanent mould and high-pressure die-castings of the AlMg$_{5}$Si$_{2}$Mn alloy is investigated by differential scanning calorimetry, microhardness measurements, transmission electron microscopy, and energy dispersive X-ray analysis. Inside the $\alpha$-Al grains, the curved plate-like precipitates are detected for both alloys. Examination of these precipitates reveals a number of features, such as follow: (i) the composition of the precipitates is very close to the stoichiometric Mg$_{2}$Si compound; (ii) precipitates are aligned along dislocations; (iii) the precipitate density is much higher for the high-pressure die-castings, where the $\alpha$-Al matrix contains more dislocations than in permanent mould castings; (vi) precipitates lie inside the $\alpha$-Al grains, where they are randomly distributed. Precipitates are not observed among the Mg$_{2}$Si lamellas. Most likely, these precipitates are $\beta^{''}$-phase, and the mechanism of their formation is the heterogeneous nucleation on dislocations.

Key words: precipitates, element distribution, natural hardening, aluminium casting alloy.



PACS: 61.66.Dk, 61.72.Ff, 61.72.Qq, 62.20.Qp, 81.05.Bx, 81.10.Fq, 81.30.Mh

Citation: V. V. Boyko, T. Link, and K. V. Mykhalenkov, Structural Characterization and Precipitation in AlMg$_{5}$Si$_{2}$Mn Alloy, Metallofiz. Noveishie Tekhnol., 36, No. 12: 1597—1608 (2014)

  1. M. C. Wuth, H. Koch, and A. J. Franke, Casting Plant and Technology International, 16: 12 (2000).
  2. U. Hielscher, H. Sternau, H. Koch, and A. J. Franke, Light Metals 1996 (Ed. W. Hale) (TMS: 1996), p. 933.
  3. S. Otarwanna et al., Met. Mater. Trans. A, 40A: 1645 (2009). Crossref
  4. T. Petkov et al., BHM Berg- und Huttenmannische Monatsheft, 158, Iss. 3: 1 (2013).
  5. G. K. Sigworth, H. Koch, and P. Krug, 40th Annual Conference of Metallurgists and Electrometallurgy. Light Metals Symposium (August 26–29, 2001, Toronto), p. 349.
  6. G. Wang, L. Yan, G. Ren, and Z. Zhao, J. Mater. Eng. Performance, 20: 399 (2011). Crossref
  7. Q. G. Wang and C. J. Davidson, J. Mat. Sci., 36: 739 (2001). Crossref
  8. O. M. Barabash, O. V. Sulzhenko, T. N. Legkaya, and N. P. Korzhova, J. Phase Equilibria, 22: 5 (2001). Crossref
  9. L. F. Mondolfo, Aluminum Alloys: Structure and Properties (London–Boston: Butterworths: 1976), p. 678.
  10. C. Ravi and C. Wolverton, Acta Mater., 52: 4213 (2004). Crossref