Microstructural evolution and mechanical properties of rheocast Al-7.1WT%Si alloy

  • Mehdi Raeissia
  • Behzad Niroumandb
Keywords: Semisolid rheocasting, particle density, Dendrite arm detachment, Ripening model, Tensile strength.


Effects of Semi-Solid Rheocasting (SSR) process on the structure and mechanical properties of Al-7.1wt%Si alloy were studied. The results showed that the non-dendritic structure could be formed by a short stirring period below liquidus temperature provided that stirring was combined with localized rapid heat extraction from the melt. The effect was examined by calculation of the time needed for detachment of dendrite arms at the initial stages of solidification and was associated with a large particle density in the rheocast slurry. Samples processed in semisolid state had lower porosity, higher tensile strength and higher elongation than that processed in fully-liquid state. The SSR- processed sample had a lower tensile strength but a higher elongation than the sample cooled without localized cooling and stirring. It was suggested that the lower strength of SSR-processed alloy was related to the inability of the α-particles to restrain crack propagation through the brittle eutectic matrix.


M.C. Flemings: Metal. Trans., 1991, 22A, 957-981.

Z. Fan: Int. Mater. Rev. 47 (2002) 49-85.

H. Kaufmann, P.J. Uggowitzer, Adv. Eng. Mater. 3 (2001) 963-967.

S. Nafisi, R. Ghomashchi, Mater. Sci. Eng. 415A (2006) 273-285.

H.M. Guo, X.J. Yang, J.X. Wang, Mater. Sci. Forum 628 (2009) 477-482.

R. Canyook, J. Wannasin, S. Wisuthmethangkul, M.C. Flemings, Acta Mater. 60 (2012) 3501–3510.

E.C. Legoretta, H.V. Atkinson, H. Jones, J. Mater. Sci. 43 (2008) 5448-5455.

R.A. Martinez, A. Karma, M.C. Flemings: Metal. Mater. Trans. 37A (2006) 2807-2815.

M. Payandeh, Anders E.W. Jarfors, M. Wessén, Metal. Mater. Trans. 47A (2016) 1215-1228.

M. Reisi, B. Niroumand: J. Alloys Compd. 475 (2009) 643–647.

M. Reisi, B. Niroumand: J. Alloys Compd 470 (2009) 413–419.

M. Reisi, B. Niroumand, , J. Mater. Chem. Phys. 135 (2012) 738-748.

Ch. -A. Gandin: Acta Mater. 48 (2000) 2483-2501.

G. Heiberg, Ch. -A. Gandin, H. Goerner, L. Arnburg: Metall. Mater. Trans. 35A (2004) 2981-2991.

ASTM E8/E8M-08 Standard Test Methods for Tension Testing of Metallic Materials.

R.B. Bird, W.E. Stewart, E.N. Lightfoot: ‘Transport Phenomena’ 2nd edn, Wiley, New York, 2002.

W. Kurz, D.J. Fisher: ‘Fundamentals of Solidification’, 4th edn, Trans. Tech. Publication, Switzerland, 1998.

T.Z. Kattamis, U.T. Holmberg, M.C. Flemings: J. Inst. Met. 95 (1967) 343-347.

D.B. Spencer, R. Mehrabian, M.C. Flemings: Met. Trans. 3 (1972) 1925-1932.

A.K. Dahle, D.H. Stjohn: Acta Mater. 47 (1999) 31-41.

A. Vogel, R.D. Doherty, B.C. Cantor: Proc. Conf. on ‘Solidification and Casting of Metals’, Metals Society, Sheffield, UK, 1977, p. 518.

A.G. Evans, A.H. Heuer, D.L. Porter: Proc. 4th Int. Conf. on Fracture, Waterloo, 1977, University of Waterloo Press, p.529.

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