The usage of computer-aided cooling curve thermal analysis to optimise eutectic refiner and modifier in Al–Si alloys
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Bismuth, antimony and strontium concentrations were optimised to alter the eutectic Al–Si phase in a commercial Al–Si–Cu–Mg alloy by way of computer-aided cooling curve thermal analysis. The results show that the eutectic growth temperature shifted to lower temperatures for all three inoculants. However, addition of Sr resulted in more depression of growth temperature compared with Bi and Sb. No further significant changes were observed with increasing the concentrations to more than 1, 0.5 and 0.04 wt% of Bi, Sb and Sr, respectively. The recalescence of these concentrations, meanwhile, showed a significant increase of magnitude. A good correlation was found between the results of thermal and microstructural analysis. For Bi and Sb, the eutectic depression temperature can be used as an individual criterion to gauge optimal levels of content in the refinement of Si, whereas for Sr, both depression temperature and recalescence magnitude must be considered. Based on the observed depression in eutectic growth temperature and recalescence, it can be concluded that the optimal concentrations to refine the eutectic Al–Si phase with Bi and Sb and to modify it with Sr at the given solidification conditions were 1, 0.5 and 0.04 wt%, respectively.
KeywordsThermal analysis Refiner Modifier Al–Si alloy Solidification
The authors acknowledge Universiti Teknologi Malaysia for providing research facilities and the Ministry of Science and Technology of Malaysia for financial support under the vot 79352.
- 1.Xiufang B, Zhang Z, Xiangfa L. Effect of strontium modification on hydrogen content and porosity shape of Al–Si alloys. Mater Sci Forum. 2000;331–337:361–6.Google Scholar
- 2.Dahle AK, Nogita K, McDonald SD, Dinnis C, Lu L. Eutectic modification and microstructure development in Al–Si Alloys. Mater Sci Eng A. 2005;413–414:243–8.Google Scholar
- 4.Dasgupta R, Brown CG, Marek S. Analysis of overmodified 356 aluminum alloy. AFS Trans. 1998;96:297–310.Google Scholar
- 6.Evans WJ, Nowicki RM, Cole GS. Measuring the quality of aluminium casting alloys with microprocessor-aided thermal analysis. AFS Trans. 1985;93:199–204.Google Scholar
- 9.Riddle YW, Makhlouf MM. Characterizing solidification by non-equilibrium thermal analysis. In: Kaplan HI, editor. Magnesium technology 2003. San Diego, CA: TMS; 2003. p. 101–6.Google Scholar
- 10.Backerud L, Chai G, Tamminen J. Foundry alloys. In: Solidification characteristics of aluminum alloys, Vol. 2. Stockholm, Sweden: AFS/Skanaluminium; 1990.Google Scholar
- 11.Apelian D, Sigworth GK, Whaler KR. Assessment of grain refinement and modification of Al–Si foundry alloys by thermal analysis. AFS Trans. 1984;92:297–307.Google Scholar
- 14.Lu L, Dahle AK. Effects of combined additions of Sr and AlTiB grain refiners in hypoeutectic Al–Si foundry alloys. Mater Sci Eng A. 2006;435–436:288–96.Google Scholar
- 21.Gruzleski JE, Closset BM. The treatment of liquid aluminium–silicon alloys. Des Plains, IL: AFS; 1990. p. 95–157.Google Scholar