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Title: Halo formation of Zn-Al alloys under conventional solidification and intensive convection solidification
Authors: Yang, W
Fredriksson, H
Ji, S
Keywords: Solidification;;Microstructure;crystal growth;alloys
Issue Date: Nov-2016
Publisher: Elsevier
Citation: Journal of Alloys and Compounds, 2016, 696 pp. 460 - 469
Abstract: A halo occurred usually as an envelope of one phase around a primary phase in many alloys after solidification. Its formation mechanism was investigated for hypoeutectic, eutectic and hypereutectic compositions of Zn-Al alloys under conventional solidification and under intensive convection solidification. It was found that the Zn-rich halos occurred in the surroundings of the Al-rich primary phase for the hypereutectic Zn-Al alloys at Al>5 wt% and no halos occurred for the hypoeutectic and eutectic Zn-Al alloys at Al≤5 wt% under conventional solidification. However, the Zn-rich halos were completely absent from the Al-rich phase because of the uniform temperature distribution and enhanced mass transport under intensive convection solidification. Once the intensive convection was interrupted during solidification for the solid-liquid co-existing melt, a halo was formed on the surface of the existing Al-rich phase created either during the primary solidification or the eutectic solidification. Therefore, it was concluded that the halo formation should be a growth-dominant phenomenon not a nucleation-dominant phenomenon. And, the interaction among the solid phases and the liquid phase was responsible for the halo formation, in which the difference in the elasticity modulus and the density of the different phases resulted in the variation of strain energy in the individual phase.
ISSN: 0925-8388
Appears in Collections:Dept of Mechanical Aerospace and Civil Engineering Research Papers

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