The behaviour of submicron Y2O3 particles incorporated in a 6082 alloy was characterized by in situ X-ray microtomography during remelting and solidification. The presence and spatial distribution of the Y2O3 particles in the alloy were revealed through the dissolution of the intermetallic phase upon remelting. They were mostly found agglomerated at grain boundaries suggesting that particle pushing is likely to be the predominant mechanism in interfacial interactions. This trend was then confirmed by the direct observation of the solidification process from the fully molten state showing clusters of yttria particles pushed by growing dendrites. In addition to providing fundamental insights into the solidification of nano-composites, these results also point out potential issues in recycling these materials and the necessity to re-disperse particles after a remelting step. (C) 2015 Elsevier Ltd. All rights reserved.