In situ synchrotron tomographic investigation of the solidification of an AlMg4.7Si8 alloy. - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Acta Materialia Année : 2012

In situ synchrotron tomographic investigation of the solidification of an AlMg4.7Si8 alloy.

Résumé

The solidification sequence of an AlMg4.7Si8 alloy is imaged in situ by synchrotron microtomography. Tomograms with (1.4 mu m)(3)/voxel have been recorded every minute while cooling the melt from 600 degrees C at a cooling rate of 5 K min(-1) to 540 degrees C in the solid state. The solidification process starts with the three-dimensional evolution of the alpha-Al dendritic structure at 590 degrees C. The growth of the a-Al dendrites is described by curvature parameters that represent the coarsening quantitatively, and ends in droplet-like shapes of the secondary dendrite arms at 577 degrees C. There, the eutectic valley of alpha-Al/Mg2Si is reached, forming initially octahedral Mg2Si particles preferentially at the bases of the secondary dendrite arms. The eutectic grows with seaweed-like Mg2Si structures, with increasing connectivity. During this solidification stage Fe-aluminides form and expand as thin objects within the interdendritic liquid. Finally, the remaining liquid freezes as ternary alpha-Al/Mg2Si/Si eutectic at 558 degrees C, increasing further the connectivity of the intermetallic phases. The frozen alloy consists of four phases exhibiting morphologies characteristic of their mode of solidification: alpha-Al dendrites, eutectic alpha-Al/Mg2Si "Chinese script" with Fe-aluminides, and interpenetrating alpha-Al/Mg2Si/Si ternary eutectic. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Domaines

Matériaux

Dates et versions

hal-00728091 , version 1 (04-09-2012)

Identifiants

Citer

D. Tolnai, P. Townsend, G. Requena, L. Salvo, J. Lendvai, et al.. In situ synchrotron tomographic investigation of the solidification of an AlMg4.7Si8 alloy.. Acta Materialia, 2012, 60 (6-7), pp.2568-2577. ⟨10.1016/j.actamat.2012.01.024⟩. ⟨hal-00728091⟩
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