City Research Online

Abstract

Direct observation of mesoscale grain behaviour during semi-solid metal flow has remained significantly challenging, limiting our understanding of flow-induced defects formation. In this study, in-situ synchrotron X-ray imaging is used to quantitatively analyse grain motion, deformation, fragmentation and grain-to-grain contact interactions in a semi-solid Al-15Cu alloy subjected to controlled shear. The results reveal spatially heterogeneous grain fragmentation across zones with varying shear rates. Grain dynamics demonstrate coordinated movement between solid and liquid phases, with displacement closely correlated with local flow velocity. Force chains aligned with the flow direction facilitates grain rearrangement by promoting grains packing parallel to and separation perpendicular to the flow. The contact network evolves from initial densification to dilatancy-driven loosening, reflecting dynamic rearrangement under shear. These quantitative relationships between flow conditions and grain behaviour offer foundational insights into the precursor mechanisms of defect nucleation, advancing predictive modelling for casting processes.

Publication Type:	Article
Additional Information:	© 2026 Acta Materialia Inc. Published by Elsevier Inc. All rights are reserved. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/
Publisher Keywords:	Synchrotron radiation; Grain dynamics; 2D quantitative analysis; Casting; Aluminum alloys
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology School of Science & Technology > Department of Engineering
SWORD Depositor:	Symplectic Administrator

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