Advertisement

Metallurgical and Materials Transactions A

, Volume 34, Issue 12, pp 2887–2899 | Cite as

Microstructural effects on the tensile and fracture behavior of aluminum casting alloys A356/357

  • Q. G. Wang
Article

Abstract

The tensile properties and fracture behavior of cast aluminum alloys A356 and A357 strongly depend on secondary dendrite arm spacing (SDAS), Mg content, and, in particular, the size and shape of eutectic silicon particles and Fe-rich intermetallics. In the unmodified alloys, increasing the cooling rate during solidification refines both the dendrites and eutectic particles and increases ductility. Strontium modification reduces the size and aspect ratio of the eutectic silicon particles, leading to a fairly constant particle size and aspect ratio over the range of SDAS studied. In comparison with the unmodified alloys, the Sr-modified alloys show higher ductility, particularly the A356 alloy, but slightly lower yield strength. In the microstructures with large SDAS (>50 µm), the ductility of the Sr-modified alloys does not continuously decrease with SDAS as it does in the unmodified alloy. Increasing Mg content increases both the matrix strength and eutectic particle size. This decreases ductility in both the Sr-modified and unmodified alloys. The A356/357 alloys with large and elongated particles show higher strain hardening and, thus, have a higher damage accumulation rate by particle cracking. Compared to A356, the increased volume fraction and size of the Fe-rich intermetallics (π phase) in the A357 alloy are responsible for the lower ductility, especially in the Sr-modified alloy. In alloys with large SDAS (>50 µm), final fracture occurs along the cell boundaries, and the fracture mode is transgranular. In the small SDAS (<30 µm) alloys, final fracture tends to concentrate along grain boundaries. The transition from transgranular to intergranular fracture mode is accompanied by an increase in the ductility of the alloys.

Keywords

Material Transaction A357 Alloy Eutectic Silicon Particle Aspect Ratio Unmodified Alloy 
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.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    D.D. Goehler: Proc. of Innovations and Advancements in Aluminum Casting Technology—AFS Special Conf., City of Industry, CA, 1988, American Foundarymen’s Society, Des Plaines, IL, 1998, pp. 103–06.Google Scholar
  2. 2.
    M.C. Flemings: Solidification Processing, McGraw-Hill, New York, NY, 1974.Google Scholar
  3. 3.
    R.E. Spear and G.R. Gardner: AFS Trans., 1963, vol. 71, pp. 209–15.Google Scholar
  4. 4.
    D. Apelian, S. Shivkumar, and G. Sigworth: AFS Trans., 1989, vol. 97, pp. 727–42.Google Scholar
  5. 5.
    Z. Shan and A.M. Gokhale: Acta Mater., 2001, vol. 49, pp. 2001–15.CrossRefGoogle Scholar
  6. 6.
    S.F. Frederick and W.A. Bailey: Trans. TMS-AIME, 1968, vol. 242, p. 2063.Google Scholar
  7. 7.
    K.J. Oswalt and M.S. Misra: AFS Trans., 1980, vol. 88, pp. 845–62.Google Scholar
  8. 8.
    A. Gangulee and J. Gurland: Trans. TMS-AIME, 1967, vol. 239, pp. 269–72.Google Scholar
  9. 9.
    C.W. Meyers, A. Saigal, and J.T. Berry: AFS Trans., 1983, vol. 91, pp. 281–88.Google Scholar
  10. 10.
    C.H. Cáceres, C.J. Davidson, and J.R. Griffiths: Mater. Sci. Eng. A, 1995, vol. 197, pp. 171–79.CrossRefGoogle Scholar
  11. 11.
    A. Couture: AFS Int. Cast Met. J., 1981, vol. 6, pp. 9–17.Google Scholar
  12. 12.
    C.H. Cáceres, C.J. Davidson, J.R. Griffiths, and Q.G. Wang: Metall. Mater. Trans. A, 1999, vol. 30A, pp. 2611–18.CrossRefGoogle Scholar
  13. 13.
    J.A. Taylor, D.H. StJohn, J. Barresi, and M.J. Couper: Mater. Sci. Forum, 2000, vols. 331–337, p. 277.CrossRefGoogle Scholar
  14. 14.
    S. Chappell, T.A. Hughes, and G. Pollard: Metallography, 1970, vol. 3, pp. 235–37.CrossRefGoogle Scholar
  15. 15.
    R.C. Harris, S. Lipson, and H. Rosenthal: AFS Trans., 1956, vol. 64, pp. 470–81.Google Scholar
  16. 16.
    C.H. Cáceres, J.R. Griffiths, and P. Reiner: Acta Mater., 1996, vol. 44, pp. 15–23.CrossRefGoogle Scholar
  17. 17.
    Q.G. Wang, C.H. Cáceres, and J.R. Griffiths: AFS Trans., 1998, vol. 106, pp. 131–36.Google Scholar
  18. 18.
    A.T. Joenoes and J.E. Gruzleski: Cast Met., 1991, vol. 4 (2), pp. 62–71.Google Scholar
  19. 19.
    L. Bäckerud, G. Chai, and J. Tamminen: AFS/SKAN-Aluminum, American Foundrymen’s Society (AFS), Des Plaines, IL, USA, 1990, vol. 2, pp. 128–50.Google Scholar
  20. 20.
    Q.G. Wang and C.J. Davidson: J. Mater. Sci., 2001, vol. 36, pp. 739–50.CrossRefGoogle Scholar
  21. 21.
    W.H. Hunt, J.R. Brockenbrough, and P.E. Magnusen: Scripta Metall. Mater., 1991, vol. 25 (1), pp. 15–20.CrossRefGoogle Scholar
  22. 22.
    J. Yang, C. Cady, M.S. Hu, F. Zok, R. Mehrabian, and A.G. Evans: Acta Metall. Mater., 1990, vol. 38, pp. 2613–19.CrossRefGoogle Scholar
  23. 23.
    D.J. Lloyd: Acta Metall. Mater., 1991, vol. 39, pp. 59–71.CrossRefGoogle Scholar
  24. 24.
    W.H. Hunt: Ph.D. Dissertation, Carnegie Mellon University, Pittsburgh, PA, 1992, Order No. 9312832.Google Scholar
  25. 25.
    D. Teirlinck, M.F. Ashby, and J.D. Embury: 6th Int. Conf. on Fracture, New Delhi, India, 4–10 December 1984, Pergamon, Oxford, 1986, pp. 105–25.Google Scholar
  26. 26.
    P.E. Magnusen, D.J. Srolovitz, and D.A. Koss: Acta Metall., 1990, vol. 38, pp. 1013–22.CrossRefGoogle Scholar
  27. 27.
    Q.G. Wang and C.H. Cáceres: Mater. Sci. Eng., 1998, vol. A241, pp. 72–82.Google Scholar

Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2003

Authors and Affiliations

  • Q. G. Wang
    • 1
  1. 1.Advanced Materials Engineering, Powertrain DivisionGeneral Motors CorporationPontiac

Personalised recommendations