Subroto, Tungky, Lebon, Gerard S. B., Eskin, Dmitry G., Skalicky, Ivan, Roberts, Dan, Tzanakis, Iakovos and Pericleous, Koulis ORCID: 0000-0002-7426-9999 (2021) Numerical modelling and experimental validation of the effect of ultrasonic melt treatment in a direct-chill cast AA6008 alloy billet. Journal of Materials Processing Technology, 12. pp. 1582-1596. ISSN 0924-0136 (doi:https://doi.org/10.1016/j.jmrt.2021.03.061)

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Abstract

In this work, we study how ultrasonic cavitation melt treatment (UST) affects the temperature distribution, sump profile, and resulting microstructure in the direct-chill (DC) casting of an AA6008 aluminum alloy. Two 152 mm diameter billets were cast; one was treated with UST (UST-DC casting) in the hot top while the other was not (conventional DC casting). To investigate the temperature distribution, temperature was measured at multiple points in both billets. The sump profile was visualized by pouring Zn into the sump during casting. The microstructure was analyzed by measuring the grain size of as-cast billets. A numerical model of DC casting and UST-DC casting has been validated with the temperature measurements across the billets, and the experimental results agrees well with the numerical model. It is found that the sump profile quantification with thermocouple measurements is more accurate and less prone to interpretation than with Zn tracing. Numerical simulation results show that UST application in the hot top with sonotrode position at 20 mm above the graphite ring level depresses the liquidus isotherm but does not affect the solidus isotherm, resulting in a thinner transition region compared with conventional DC casting. Grain structure analysis verifies that structure refinement with UST has been achieved at the given sonotrode position. The strongest grain refinement was at the center of the billet with the average grain size 50% smaller than that without UST. The results are discussed in terms of the known mechanisms of UST, i.e. dendrite fragmentation and deagglomeration of nucleating substrates.

Item Type:	Article
Additional Information:	© 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Uncontrolled Keywords:	Ultrasonic melt treatment, numerical modeling, direct-chill (DC) casting, aluminum alloy, temperature measurement
Subjects:	Q Science > QA Mathematics > QA75 Electronic computers. Computer science
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science Faculty of Engineering & Science > Centre for Numerical Modelling & Process Analysis (CNMPA) Faculty of Engineering & Science > Centre for Numerical Modelling & Process Analysis (CNMPA) > Computational Science & Engineering Group (CSEG) Faculty of Engineering & Science > School of Computing & Mathematical Sciences (CMS)
Last Modified:	23 May 2022 09:56
URI:	http://gala.gre.ac.uk/id/eprint/32161

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