Influence of gravity level on Columnar-to-Equiaxed Transition during directional solidification of Al-20 wt.% Cu alloys

L. Abou-Khalil , G. Salloum-Abou-Jaoude , G. Reinhart , C. Pickmann , G. Zimmermann , H. Nguyen-Thi (1)

1 IM2NP - Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

Solidification experiments on refined and non-refined Al-Cu alloys were carried out on Earth and during two parabolic flights to investigate the influence of gravity level upon solidification dynamics. In situ and real-time monitoring of the microstructure formation was characterized by using an X-ray radiography device based on a microfocus X-ray source. This paper presents for the first time direct observation of metal alloy directional solidification under varying gravity level. By a comparative study between the experiments, the influence of gravity on fragmentation and dendrite fragments transport was enlightened. In addition, a spectacular transition from a columnar to a fully equiaxed microstructure was revealed when there is a sharp increase of gravity level. It was shown that this phenomenon is a consequence of a sudden increase of the liquid undercooling ahead of the columnar front accompanying the change in hydrostatic pressure. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Domaines: Micro et nanotechnologies/Microélectronique

L. Abou-Khalil, G. Salloum-Abou-Jaoude, G. Reinhart, C. Pickmann, G. Zimmermann, et al.. Influence of gravity level on Columnar-to-Equiaxed Transition during directional solidification of Al-20 wt.% Cu alloys. Acta Materialia, 2016, 110, pp.44-52. ⟨10.1016/j.actamat.2016.03.007⟩. ⟨hal-01434968⟩