Investigation of particle dynamics and solidification in a two-phase system by neutron radiography

We investigate directional solidification of the melt with solid inclusions by means of a non- invasive imaging technique - neutron radiography. For the first time results have revealed particle trapping in the solidifying melt at macro scale. It is shown that particle solidification in volume can be achieved when liquid and solid phases form a mushy zone. Experiments were performed using a rectangular vessel containing tin (Sn) which was electromagnetically stirred and directionally solidified. Information about the recirculating flow was gathered by tracing 355-500 µm gadolinium particles which visualize the flow field and the state of matter at any given time. The findings show that metallurgical challenges, e.g., stirring and homogeneously dispersing ceramic reinforcement material in metal matrix composites, could be solved by ap- plying electromagnetic treatment while the melt is in a semi-solid state. Key words: directional solidification, mushy zone, neutron radiography, neutron imaging, particle trapping.