Metastable Dendrite Morphologies in Impulse Atomized Droplets of Al-Alloys




1st Paragraph: Cubic type crystals of metallic alloys such as Al-Cu, Al-Fe and Al-Ni generally grow along <100> directions due to the anisotropy of the solid-liquid interfacial energy. Under rapid solidification conditions, dendrites growth may deviate from <100> and unusual and complex morphologies can develop. Rapid solidification of Al-alloy droplets of various composition was carried out using Impulse Atomization (a type of drop tube) in an inert atmosphere to study the microstructures forming at different liquid droplet cooling rates and primary phase undercoolings. Synchrotron Xray micro-tomography and electron backscattered diffraction (EBSD) were used to fully characterize growth morphologies of impulse atomized Al-4.5Cu and Al-4.5Cu-0.4Sc droplets. Four distinct morphologies were evidenced (Figure 1).

Authors: J. Valloton, A.-A. Bogno, and H. Henein

Keywords: Aluminum alloys, Impulse Atomization, Rapid Solidification, Growth Directions

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3 pages


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