Abstract
The present study is part of a larger study where the effectiveness of different types of grain refiners in strontium-modified hypoeutectic alloys was evaluated. Silicon was shown to affect the mechanism of nucleation of α-aluminum. To explore this phenomenon, an investigation was carried out on hypereutectic A390.1 alloy containing 17.3%Si to establish the role of primary silicon crystallization on subsequent α-aluminum and silicon eutectic reactions with different grain refiner additions. The alloy was modified with 0.02%Sr as before, and the same three-grain refiners: Al–10%Ti, Al–5%Ti–1%B, and Al–4%B master alloys, were used at controlled addition levels. The liquid metal was held at 750 °C for periods up to 120 min during which the molten metal was continuously stirred. The results show that addition of 0.1%Ti (using Al–10%Ti) to A390.1 alloy modified with 0.02%Sr results in reducing the initial grain size by about 20% only, due to transformation of Al3Ti phase to (Al,Si)2Ti phase which is a poor grain refiner. The stability of the (Al,Si)2Ti phase increases with the increase in the alloy Si content. The formation of (Al,Si)2Ti also reduces the undercooling caused by Sr addition, reducing the degree of morphology modification. Additionally, boron has a strong affinity to react with Sr, forming the compound SrB6, resulting in no grain refining or “poisoning,” regardless of the added amount of B or the holding time. Combined addition of Sr and B, however, improves the modification of the eutectic Si. In general, due to the high Si content of A390.1 alloy, it is difficult to achieve an appreciable degree of grain refining.
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig1_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig2_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig3_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig4_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig5_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig6_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig7_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig8_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig9_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig10_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig11_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig12_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig13_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig14_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig15_HTML.gif)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig16_HTML.jpg)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs40962-017-0164-5/MediaObjects/40962_2017_164_Fig17_HTML.gif)
Similar content being viewed by others
References
H. Liao, Y. Sun, G. Sun, Effect of Al–5Ti–1B on the microstructure of near-eutectic Al–13%Si alloys modified with Sr. J. Mater. Sci. 37, 3489–3495 (2002)
H. Liao, Y. Sun, G. Sun, Correlation between mechanical properties and amount of dendritic α-Al phase in as-cast near-eutectic Al–11,6%Si alloys modified with strontium. Mater. Sci. Eng. A 35, 62–66 (2002)
H. Liao, G. Sun, Mutual poisoning effect between Sr and B in Al–Si casting alloys. Scr. Mater. 48, 1035–1039 (2003)
P.D. Lee, T.C. Lindley, The influence of strontium and TiB2 additions on the formation of porosity in aluminum castings and their effect on final fatigue properties. Foundry Trade J. 179, 216–219 (2005)
H. Dieringa, N. Hort, K.U. Kaine, Novel grain refiner for hypo- and hyper-eutectic Al–Si alloys. Mater. Sci. Forum 690, 49–52 (2011)
C.G. Shivaprasad, K. Aithal, S. Narendranath, M. Pudukottah, Effect of combined grain refinement and modification on microstructure and mechanical properties of hypoeutectic, eutectic and hypereutectic Al–Si alloys. Int. J. Microstruct. Mater. Prop. 10, 247–284 (2015)
M. Zuo, D.G. Zhao, X.Y. Teng, H.R. Geng, Z.S. Zhang, Effect of P and Sr complex, modification on Si phase in hypereutectic Al–30Si alloys. Mater. Des. 47, 857–864 (2013)
S.S. Shin, E.S. Kim, G.Y. Yeom, J.C. Lee, Modification effect of Sr on the microstructures and mechanical properties of Al–10.5Si–2.0Cu recycled alloy for die casting. Mat. Sci. Eng. A Struct. 532, 151–157 (2012)
K.G. Basavakumar, P.G. Mukunda, M. Chakraborty, Dry sliding wear behaviour of Al–12Si and Al–12Si–3Cu cast alloys. Mater. Des. 30, 1258–1267 (2009)
T.M. Chandrashekharaiah, S.A. Kori, Effect of grain refinement and modification on the dry sliding wear behaviour of eutectic Al–Si alloys. Tribol. Int. 42, 59–65 (2009)
C. Drum, H.I. Laukli, O.S. Hopperstad, M. Langseth, Structural behaviour of Al–Si die- castings: experiments and numerical simulations. Eur. J. Mech. A 28, 1–13 (2009)
G.K. Sigworth, T.A. Kulun, Grain refinement of aluminum casting alloys. Int. J. Metalcast. 115, 31–40 (2007)
M. Nowak, L. Bolzoni, N. Hari Babu, Grain refinement of Al–Si alloys by Nb–B inoculation. Part I: Concept development and effect on binary alloys. Mater. Des. 5, 366–375 (2015)
Y.C. Lee, A.K. Dahle, D.H. StJohn, J.E.C. Hutt, The effect of grain refinement and silicon content on grain formation in hypoeutectic Al–Si alloys. Mater. Sci. Eng. A 259, 43–52 (1999)
N.L. Yue, L. Lu, M.O. Lai, Application of thermodynamic calculation in the in situ process of Al/TiB2. Compos. Struct. 47, 691–694 (1999)
D. Qiu, J.A. Taylor, M.-X. Zhang, P.M. Kelly, A mechanism for the poisoning effect of silicon on the grain refinement of Al–Si alloys. Acta Mater. 55, 1447–1456 (2007)
W. Khalifa, F.H. Samuel, J.E. Gruzleski, Nucleation of solid aluminum on inclusion particles injected into Al–Si-Fe alloys. Metall. Mater. Trans. A 35A, 3233–3250 (2004)
L. Heusler, W. Schneider, Influence of alloying elements on the thermal analysis results of Al–Si cast alloys. J. Light Met. 2, 17–26 (2002)
H. Liao, M. Zhang, H. Wang, G. Dong, G. Sun, in Proceedings of Materials Science & Technology, Conference, 16–20 September 2007, Detroit, MI
J. Tamminen, Ph.D. Thesis, Stockholm University, Stockholm, 1988
S. Hegde, K.N. Prabhu, Modification of eutectic silicon in Al–Si alloys. J. Mater. Sci. 43, 3009–3027 (2008)
M. Johnsson, Grain refinement of aluminium studied by use of a thermal analytical technique. Thermochimica Acta 256, 107–121 (1995)
M. Johnsson, L. Backerud, G.K. Sigworth, Study of the mechanism of grain refinement of aluminum after additions of Ti- and B-containing master alloys. Metall. Trans. A 24A, 481–491 (1993)
S. McDonald, K. Nogita, A. Dahle, Eutectic nucleation in Al–Si alloys. Acta Mater. 52, 4273–4280 (2004)
J. Asensio-Lozano, B. Suarez-Pena, Effect of the addition of refiners and/or modifiers on the microstructure of die cast Al–12Si alloys. Scr. Mater. 54, 943–947 (2006)
H. Liao, M. Zhang, Q. Wu, H. Wang, G. Sun, Refinement of eutectic grains by combined addition of strontium and boron in near-eutectic Al–Si alloys. Scr. Mater. 57, 1121–1124 (2007)
L. Wang, X.F. Bian, S.J. Yuan, Refining effect of boron on eutectic silicon in hypoeutectic Al–Si alloys. Acta Metall. Sin. 12, 611–616 (1999)
K. Nogita, A.K. Dahle, Effect of boron on eutectic modification of hypoeutectic Al–Si alloys. Scr. Mater. 48, 307–313 (2003)
Acknowledgements
The authors would like to thank Amal Samuel, Hicham Farid and Mohamed Gamal for enhancing the quality of the images and drawings presented in this article.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Tahiri, H., Samuel, A.M., Doty, H.W. et al. Effect of Sr–Grain Refiner–Si Interactions on the Microstructure Characteristics of Al–Si Hypereutectic Alloys. Inter Metalcast 12, 307–320 (2018). https://doi.org/10.1007/s40962-017-0164-5
Published:
Issue Date:
DOI: https://doi.org/10.1007/s40962-017-0164-5