Metastable Dendrite Morphologies in Aluminum Alloys

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  • Cubic metallic alloys generally grow along 〈100〉 directions due to the anisotropy of the solid-liquid interfacial energy. Under rapid solidification conditions, dendrites may deviate from 〈100〉 and develop unusual morphologies. Here, Al-alloy droplets (Al-4.5Cu, Al-10Si, Al-1.9Fe, Al-33Cu, all in wt%) were rapidly solidified using Impulse Atomization to study the microstructures forming at different cooling rates and undercoolings. Growth morphologies of Al-4.5Cu droplets were characterized using X-ray micro-tomography and EBSD. Al-dendrites were found to grow along either 〈100〉 or a more unusual 〈111〉 depending on the solidification conditions. Also, a transition from 〈111〉 to 〈100〉 in the same droplet was observed. These uncommon growth directions were also observed in other Al-alloys. In Al-1.9Fe droplets, a change in dendrite growth direction from 〈100〉 to 〈111〉 was observed, while 〈110〉 growth directions were detected in Al-10Si samples. These experimental observations will be related to their solidification conditions using Solidification Continuous Cooling Transformation diagrams.

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    Attribution-NonCommercial-NoDerivatives 4.0 International
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