Journal of Materials Science

, Volume 47, Issue 11, pp 4716–4725 | Cite as

Composition segregation in semi-solid metal cast AA7075 aluminium alloy

  • S. L. GeorgeEmail author
  • R. D. Knutsen


The composition distribution and microstructural evolution associated with the characteristic globular grain structure in semi-solid metal cast AA7075 aluminium alloy has been investigated. The primary globular grains possess uniform composition over nearly 90% of their diameter with fluctuations only occurring in the near surface of the individual grains. The inter-globular regions are solute rich and contain non-equilibrium eutectic. The segregation pattern in semi-solid cast structures occurs over a much greater length-scale than the dendritic pattern prevalent in conventional castings and it is proposed that the distinction arises from predominant planar growth of the α-primary globular grains during the SSM conditioning stage. Examination of the in-grain structure using electron backscattered diffraction revealed a quasi-periodic fluctuation in misorientation that may have arisen from local perturbations on the planar solid interface as solidification progressed. Homogenisation prior to artificial ageing is severely compromised by the undesirable segregation pattern.


Segregation Pattern Solute Segregation Composition Distribution Incipient Melting Globular Morphology 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



The authors gratefully acknowledge the financial support of the National Research Foundation of South Africa (NRF), as well as the Council for Scientific and Industrial Research (CSIR) in Pretoria for the supply of samples.


  1. 1.
    Fan Z (2002) Int Mater Rev 47:1CrossRefGoogle Scholar
  2. 2.
    Chayong S, Atkinson HV, Kaprinos P (2005) Mater Sci Eng A 390:3CrossRefGoogle Scholar
  3. 3.
    Nadella R, Eskin DG, Du Q, Katgerman L (2008) Prog Mater Sci 53:421CrossRefGoogle Scholar
  4. 4.
    Bruwer R, Wilkins JD, Ivanchev LH, Rossouw P, Damm OFRA, (2008) Patent number: US7368690Google Scholar
  5. 5.
    Curle UA (2010) Trans Nonferrous Met Soc China 20:1719CrossRefGoogle Scholar
  6. 6.
    Teghtsoonian E (1951) Can J Phys 29:370CrossRefGoogle Scholar
  7. 7.
    George SL, Knutsen RD (2011) JSAIMM 111:183Google Scholar
  8. 8.
    Fan X, Jiang D, Meng Q, Zhang B, Wang T (2006) Trans Nonferrous Met Soc 16:577CrossRefGoogle Scholar
  9. 9.
    Deschamps A, Brechet Y, Livet F (1999) J Mater Sci Technol 15:993Google Scholar
  10. 10.
    Yang D, (2006) PhD Thesis, University of QuebecGoogle Scholar
  11. 11.
    Fan X, Jiang D, Meng Q, Zhong L (2006) Mater Lett 60:1475CrossRefGoogle Scholar
  12. 12.
    Chena K, Liu H, Zhang Z, Li S, Todd RI (2003) J Mater Process Technol 142:190CrossRefGoogle Scholar
  13. 13.
    Flemings MC, Riek RG, Young KP (1976) Mater Sci Eng 25:103CrossRefGoogle Scholar
  14. 14.
    Vogel A, Doherty RD, Cantor B (1977) In: Proceedings of solidification and casting of metals conference, Sheffield, p. 518Google Scholar
  15. 15.
    Pilling J, Hellawell A (1996) Metall Trans A 27:229CrossRefGoogle Scholar
  16. 16.
    Doherty RD, Lee HI, Feest EA (1984) Mater Sci Eng 65:181CrossRefGoogle Scholar
  17. 17.
    Mullis AM (1999) Acta Mater 47:1783CrossRefGoogle Scholar
  18. 18.
    Fan Z, Lui G (2005) Acta Mater 53:4345CrossRefGoogle Scholar
  19. 19.
    Ji S, Fan Z (2002) Metall Trans A 33:3511CrossRefGoogle Scholar
  20. 20.
    Molenaar JMM, Salemans FWHC, Katgerman L (1985) J Mater Sci 20:4335. doi: 10.1007/BF00559322 CrossRefGoogle Scholar
  21. 21.
    Fabietti LM, Travedi R (1997) J Cryst Growth 173:503CrossRefGoogle Scholar
  22. 22.
    Henry S, Minghetti T, Rappaz M (1998) Acta Mater 46:6431CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  1. 1.Department of Mechanical Engineering, Centre for Materials EngineeringUniversity of Cape TownRondeboschSouth Africa

Personalised recommendations