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Dendritic Growth Morphologies in Al-Zn Alloys—Part II: Phase-Field Computations

Dantzig, J. ; Di Napoli, Paolo ; Friedli, J. ; Rappaz, M.

In: Metallurgical and Materials Transactions A, 2013, vol. 44, no. 12, p. 5532-5543

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    Titre
    • Dendritic Growth Morphologies in Al-Zn Alloys—Part II: Phase-Field Computations
    Auteur
    • Dantzig, J.. Laboratoire de Simulation des Matériaux, Ecole Polytechnique Fédérale de Lausanne, EPFL-STI-IMX-LSMX, Station 12, 1015, Lausanne, Switzerland
    • Di Napoli, Paolo. Laboratoire de Simulation des Matériaux, Ecole Polytechnique Fédérale de Lausanne, EPFL-STI-IMX-LSMX, Station 12, 1015, Lausanne, Switzerland
    • Friedli, J.. Laboratoire de Simulation des Matériaux, Ecole Polytechnique Fédérale de Lausanne, EPFL-STI-IMX-LSMX, Station 12, 1015, Lausanne, Switzerland
    • Rappaz, M.. Laboratoire de Simulation des Matériaux, Ecole Polytechnique Fédérale de Lausanne, EPFL-STI-IMX-LSMX, Station 12, 1015, Lausanne, Switzerland
    Type de document
    • Postprint
    Langue
    • Inglese
    Publié dans
    • Metallurgical and Materials Transactions A, 2013, vol. 44, no. 12, p. 5532-5543. Springer US; http://www.springer-ny.com
    Autre version électronique
    Classification
    • Technologie, Sciences de l'ingénieur
    Identifiant OAI-PMH
    • oai:doc.rero.ch:316749
    Summary
    In Part I of this article, the role of the Zn content in the development of solidification microstructures in Al-Zn alloys was investigated experimentally using X-ray tomographic microscopy. The transition region between $${\langle{100}\rangle}$$ 〈 100 〉 dendrites found at low Zn content and $${\langle{110}\rangle}$$ 〈 110 〉 dendrites found at high Zn content was characterized by textured seaweed-type structures. This Dendrite Orientation Transition (DOT) was explained by the effect of the Zn content on the weak anisotropy of the solid-liquid interfacial energy of Al. In order to further support this interpretation and to elucidate the growth mechanisms of the complex structures that form in the DOT region, a detailed phase-field study exploring anisotropy parameters' space is presented in this paper. For equiaxed growth, our results essentially recapitulate those of Haxhimali etal.[1] in simulations for pure materials. We find distinct regions of the parameter space associated with $${\langle{100}\rangle}$$ 〈 100 〉 and $${\langle{110}\rangle}$$ 〈 110 〉 dendrites, separated by a region where hyperbranched dendrites are observed. In simulations of directional solidification, we find similar behavior at the extrema, but in this case, the anisotropy parameters corresponding to the hyperbranched region produce textured seaweeds. As noted in the experimental work reported in Part I, these structures are actually dendrites that prefer to grow misaligned with respect to the thermal gradient direction. We also show that in this region, the dendrites grow with a blunted tip that oscillates and splits, resulting in an oriented trunk that continuously emits side branches in other directions. We conclude by making a correlation between the alloy composition and surface energy anisotropy parameters