The Grain Refinement of Al-Si Alloys and the Cause of Si Poisoning: Insights Revealed by the Interdependence Model

Abstract:

Recent work has extended the Interdependence Model to the prediction of grain size of aluminium alloys when refined by Al-Ti-B master alloys. The relative contribution of Ti solute and TiB₂ particles to the as-cast grain size was determined indicating the optimum level of addition required to provide cost effective use of master alloy. This paper quantifies the effect of Al5Ti1B master alloy additions on the grain size of Al-Si alloys. The Al-Si system is a special case where additions of Si above a few percent poison grain refinement resulting in larger grain sizes. Consideration of the complicating effect of Si poisoning on the prediction of the grain size of these alloys and possible approaches to dealing with these complications are presented.

• Periodical: Materials Science Forum (Volumes 794-796)
• Pages: 161-166
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.794-796.161
• Online since: June 2014
• Authors: Mark Easton, Arvind Prasad, David H. St. John*
• Keywords: Aluminum (Al), Grain Refinement, Master Alloys, Solidification

References

[1] Easton MA, StJohn DH, Prasad A. Grain refinement of aluminium alloys: recent developments in predicting the as-cast grain size of alloys refined by Al-Ti-B master alloys. Light Metals 2014. San Diego, CA: The Metals, Minerals and Materials Society, 2014. p. accepted for publication.

DOI: 10.1002/9781118888438.ch156

[2] Qian M, Cao P, Easton MA, McDonald SD, StJohn DH. An analytical model for constitutional supercooling-driven grain formation and grain size prediction. Acta Mater. 2010; 58: 3262.

DOI: 10.1016/j.actamat.2010.01.052

[3] StJohn DH, Qian M, Easton MA, Cao P. The Interdependence Theory: the relationship between grain formation and nucleant selection. Acta Mater. 2011; 59: 4907.

DOI: 10.1016/j.actamat.2011.04.035

[4] StJohn DH, Easton MA, Qian M, Taylor JA. Grain Refinement of Magnesium Alloys: A Review of Recent Research, Theoretical Developments, and Their Application. Metall. Mater. Trans. A 2013; 44: 2935.

DOI: 10.1007/s11661-012-1513-x

[5] Easton MA, StJohn DH. An analysis of the relationship between grain size, solute content and the potency and content of nucleant particles. Metall. Mater. Trans. A 2005; 36A: (1911).

DOI: 10.1007/s11661-005-0054-y

[6] Johnsson M, Bäckerud L. The Influence of Composition on Equiaxed Crystal Growth Mechanisms and Grain Size in Al Alloys. Z. Metallkde. 1996; 87: 216.

DOI: 10.1515/ijmr-1996-870312

[7] Johnsson M. Influence of Si and Fe on the grain refinement of Al. Z. Metallkde. 1994; 85: 781.

[8] McKay BJ, Schumacher P. An investigative Study of Si Poisoning in Al-Si Alloys using the Metallic Glass Technique. In: Chu MG, Granger DA, Han Q, editors. Solidification of Aluminum Alloys. Charlotte, NC: The Minerals, Metals and Materials Society, 2004. p.157.

[9] Quested TE, Dinsdale AT, Greer AL. Thermodynamic evidence for a poisoning mechanism iin the Al-Si-Ti system. Mater. Sci. Technol. 2006; 22: 1126.

DOI: 10.1179/174328406x114234

[10] Qiu D, Taylor JA, Zhang M-X, Kelly PM. A mechanism for the poisoning effect of silicon on the grain refinement of Al–Si alloys. Acta Mater. 2007; 55: 1447.

DOI: 10.1016/j.actamat.2006.09.046

[11] Birol Y. Effect of solute Si and Cu on grain size of aluminium alloys. Inter. J. Cast Metals Res. 2013; 26: 22.

DOI: 10.1179/1743133612y.0000000023

[12] Lee YC, Dahle AK, StJohn DH, Hutt JEC. The Effect of Grain Refinement and Silicon Content on Grain Formation in Hypoeutectic Al-Si Alloys. Mater. Sci. Engng. A 1999; 259: 43.

DOI: 10.1016/s0921-5093(98)00884-3

[13] Easton MA, StJohn DH. The Partitioning of Titanium during the Solidification of Aluminium Alloys. Mater. Sci. Technol. 2000; 16: 993.

DOI: 10.1179/026708300101508946

[14] Bäckerud L, Król E, Tamminen J. Solidification Characteristics of Aluminium Alloys Vol. 1: Skanaluminium, Universitetsforlaget AS, Oslo, Norway, (1986).

[15] Jigajinni SM, Venkateswarlu K, Kori SA. Computer aided cooling curve analysis for Al-5Si and Al-11Si alloys. Inter. Jnl. Eng. Sci. Technol. 2011; 3: 257.

DOI: 10.4314/ijest.v3i6.21

[16] Hutt J. The origin of equiaxed crystals and the grain size transition in aluminium-silicon alloys. Department of Mining, Minerals and Materials Engineering. Brisbane, Australia: The University of Queensland, (2001).

[17] Hutt JEC, StJohn DH, Hogan L, Dahle AK. Equiaxed Solidification of Al-Si Alloys. Mater. Sci. Technol. 1999; 15: 495.

DOI: 10.1179/026708399101506184

[18] Chai G, Bäckerud L, Arnberg L. Relation Between Grain Size and Coherency Parameters in Aluminium Alloys. Mater. Sci. Technol. 1995; 11: 1099.

DOI: 10.1179/mst.1995.11.11.1099

[19] Prasad A, Yuan L, Lee PD, StJohn DH. Modelling of the Nucleation-Free Zone Formed during the Initial Transient of Grain Formation. TMS2013 Annual Meeting Supplemental Proceedings: TMS (The Minerals, Metals & Materials Society), 2013. p.501.

DOI: 10.1002/9781118663547.ch62

[20] Prasad A, Yuan L, Lee PD, StJohn DH. The Interdependence model of grain nucleation: A numerical analysis of the Nucleation-Free Zone. Acta Mater. 2013; 61: 5914.

DOI: 10.1016/j.actamat.2013.06.015