Abstract
In this paper we made an attempt to assess the solidification and flow behavior of the AlSi7Mg alloy melt flowing down the cooling slope, by calculating the Reynolds number of the flowing melt. It has been found that the length of the laminar regime within the flowing melt (low-convection flow) depends on the angle of slope. The microstructure of as-cast AlSi7Mg alloy processed by low-convection-casting using cooling slope method has been studied. The microstructure reveals dendritic primary α-Al phase with fine fibrous eutectic silicon in the interdendritic regions. The modification of eutectic silicon occurs predominately by the shearing of the solute-rich liquid between the primary α-Al dendrites prior to eutectic solidification as it flows down the cooling slope. Nucleation and growth of the primary silicon dendrites was also observed, which confirms earlier reports on three-layer theory. The mechanism responsible for the refinement of eutectic phase is the enhanced heterogeneous nucleation in the last liquid to solidify.
Similar content being viewed by others
References
D.B. Spencer, R. Mehrabian, and M.C. Flemings, Rheological Behaviour of Sn-15Pb in the Crystallization Range, Metall. Mater. Trans. B, 1972, 3, p 1925–1932
M.C. Flemings, Behaviour of Metal Alloys in the Semi-Solid State, Metall. Mater. Trans. A, 1991, 22(5), p 957–981
Z. Fan, Semisolid Metal Processing, Int. Mater. Rev., 2002, 47, p 49–85
D.H. Kirkwood, Semisolid Metal Processing, Int. Mater. Rev., 1994, 39(5), p 173–189
H.V. Atkinson, Modelling the Semisolid Processing of Metallic Alloys, Prog. Mater Sci., 2005, 50, p 341–412
A.M. Kliauga and M. Ferrante, Liquid Formation and Microstructural Evolution During Re-heating and Partial Melting of an Extruded A356 Aluminium Alloy, Acta Mater., 2005, 53, p 345–356
E.A. Vieira and M. Ferrante, Prediction of Rheological Behaviour and Segregation Susceptibility of Semi-Solid Al-Si Alloys by a Simple Back Extrusion Test, Acta Mater., 2005, 53, p 5379–5386
S. Nafisi, O. Lashkari, R. Ghomashchi, F. Ajersch, and A. Charette, Microstructure and Rheological Behaviour of Grain Refined and Modified Semi-Solid A356 Al-Si Slurries, Acta Mater., 2006, 54, p 3503–3511
F. Taghavi and A. Ghassemi, Study on the Effects of the Length and Angle of Inclined Plate on the Thixotropic Microstructure of A356 Aluminium Alloy, Mater. Des., 2009, 30, p 1762–1767
Y. Birol, Cooling Slope Casting and Thixoforming of Hypereutectic A390 Alloy, J. Mater. Process. Technol., 2008, 207, p 200–203
T. Haga and P. Kapranos, Billetless Simple Thixo-Forming Process, J. Mater. Process. Technol., 2002, 130–131, p 594–598
E.C. Legoretta, H.V. Atkinson, and H. Jones, Cooling Slope Casting to Obtain Thyrotrophic Feedstock II: Observations with A356 Alloy, J. Mater. Sci., 2008, 43, p 5456–5469
T. Haga and P. Kapranos, Simple Rheocasting Processes, J. Mater. Process. Technol., 2002, 118, p 169–172
J.S. Sunitha, V. Kumar, N.S. Barekar, K. Biswas, and B.K. Dhindaw, Microstructural Evolution Under Low Shear Rates During Rheo Processing of LM25 Alloy, J. Mater. Eng. Perform., 2012, doi:10.1007/s11665-012-0166-7
K.C. Mills, Recommended Values of Thermo-Physical Properties for Selected Commercial Alloys, 2nd ed., Woohead Publishing Ltd., Cambridge, 2002, p 43
M. Mada and F. Ajersch, Rheological Model of Semi-Solid A356-SiC Composite Alloys. Part-II, Dissociation of Agglomerate Structures During Shear, Mater. Sci. Eng., A, 1996, 212, p 157–170
M.H. Robert, E.J. Zoqui, F. Tanabe, and T. Motegi, Producing Thixotropic Semi-Solid A356 Alloy-Microstructure Formation x Forming Behaviour, J. Achiev. Mater. Manuf. Eng., 2007, 20(1–2), p 19–26
J. Campbell, Complete Casting Hand Book-Metal Casting Processes, Techniques and Design, 2011, vol 1, p 255–390, http://dx.doi.org/10.1016/B978-1-85617-809-9.10006-4
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Ritwik, R., Prasada Rao, A.K. & Dhindaw, B.K. Low-Convection-Cooling Slope Cast AlSi7Mg Alloy: A Rheological Perspective. J. of Materi Eng and Perform 22, 2487–2492 (2013). https://doi.org/10.1007/s11665-013-0530-2
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11665-013-0530-2