Abstract
The effect of Mg content on the solidification and precipitation behaviour of both unmodified and Sr-modified Al-7Si-Mg casting alloys has been investigated at various solidification rates using cooling curve analysis, differential scanning calorimetry (DSC) and optical and electron microscopy. The Mg concentrations covered the range from 0.3 wt% to 0.7 wt%. The results indicate that increasing Mg content or cooling rate lowers the liquidus and binary Al-Si eutectic transformation temperatures. The latent heat of fusion of these alloys is strongly dependent on the level of Si present, but there is no observed dependence on Mg content. The solidification reactions observed under DSC are identified and it is noticed that the ternary eutectic solidification reaction L → Al + Si + Mg2Si is only observed at Mg levels of 0.6% and higher. The minor phases formed on solidification are identified and their response to solution heat treatment is examined. Increasing Mg content usually enhances precipitate hardening. However when Mg levels are increased above 0.5wt%, no apparent increase of yield strength with Mg is observed. This is correlated with dissolved Mg levels and energy released during reprecipitation.
Similar content being viewed by others
References
L. F. Mondolfo, in “Aluminium Alloys: Structure and Properties” (Butterworths, London, 1976).
G. A. Edwards, K. Stiller, G. L. Dunlop and M. Couper, Acta Met. 46 (1998) 3893.
D. L. Zhang, L. H. Zheng and D. H. Stjohn, Mat. Sci. and Tech. 14 (1998) 619.
K. T. Kashyap, S. Murali, K. S. Raman and K. S. S. Murthy, ibid. 9 (1993) 189.
C. H. CÁceres, C. J. Davidson, J. R. Griffiths and Q. G. Wang, Metallurgical and Materials Transactions A 30A (1999) 2611.
L. BÄckerud, G. Chai and J. Tamminen, “Solidification Characteristics of Aluminium Alloys, Vol. 2” (AFS/SKANAluminium, Des Plaines, IL, USA, 1990) p. 128.
D. A. Granger, R. R. Sawtell and M. M. Kersker, AFS Transactions 92 (1984) 579.
Tan Yen-Hung, Sheng-Long Lee and Yu-Lom Lin, Met. and Mater. Trans A 26A (1995) 1195.
T. Joenoes and J. E. Gruzleski, Cast Metals 4 (1991) No. 2, 62.
R. I. Mackay and J. E. Gruzleski, Int J. Cast Metals Res. 10 (1998) 255.
J. A. Taylor, D. H. St John, J. Barresi and M. J. Couper, Materials Science Forum 331–337 (2000) 277.
C. H. CÁceres, C. J. Davidson and J. R. Griffiths, Mat. Sci. and Eng. A197 (1995) 171.
Q. G. Wang and C. H. CÁceres, Materials Science Forum 242 (1996) 159.
Q. G. Wang, PhD thesis, The University of Queensland, 1997.
C. J. Simensen and T.-L. Rolfsen, Z. Metallkd 88 (1997) 142.
S. Gowri and F. H. Samuel, Metallurgical Transactions A 23A (1992) 3369.
Idem., AFS Transactions 101 (1993) 611.
B. Closset and J. E. Gruzleski, ibid. 90 (1982) 453.
S. Argyropoulos, B. Closset, J. E. Gruzleski and H. Oger, ibid. 91 (1983) 351.
P. A. Rometsch, L. Arnberg and D. L. Zhang, Int. J. Cast Metals Res. 12 (1999) 1.
J. Tamminen, Chemical Communications, No. 2, Univ. of Stockholm, 1988.
J. F. Hu and E. N. Pan, Int. J. Cast Metals Res. 10 (1998) 307.
P. N. Quested, K. C. Mills, R. F. Brooks, B. Monagham, A. T. Dinsdale, A. Day, M. J. Richardson, R. J. L. Andon, R. Taylor and H. Szelagowski, in “Modelling of Casting, Welding and Advanced Solidification Processes VII,” edited by M. Cross and J. Campbell (TMMMS, 1995) p. 407.
G. Gustafsson, T. Thorvaldsson and G. L. Dunlop, Metallurgical Transactions A 17A (1986) 45.
C. Garcia-Cordovilla, E. Louis, J. Narciso and A. Pamies, Mater. Sci. and Engg. A189 (1994) 219.
G. A. Edwards, K. Stiller, G. L. Dunlop and M. J. Couper, Materials Science Forum 217–222 (1996) 713.
S. B. Kang, L. Zhen, H. W. Kim and S. T. Lee, ibid. 217–222 (1996) 827.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Wang, Q.G., Davidson, C.J. Solidification and precipitation behaviour of Al-Si-Mg casting alloys. Journal of Materials Science 36, 739–750 (2001). https://doi.org/10.1023/A:1004801327556
Issue Date:
DOI: https://doi.org/10.1023/A:1004801327556