X-ray and neutron imaging studies on particle-laden liquid metal flow

In metallurgy, the achievement of inclusion cleanliness is a major challenge for the production of high-performance structural and functional metallic materials like aluminium alloys and steels. Ladle treat-ment of molten metal by gas injection has been employed for a long time as the processing stage is mainly responsible for the control of non-metallic inclusions in metal alloys. In these ladles, inclusion are separated by the combination of settling down and floating up. Since bigger inclusion aggregates are eliminated more easily, agglomeration is supposed to play an essential role. In case of the floata-tion process, the probabilities of collision as well as attachment between gas bubbles and solid in-clusions is strongly dependent on their sizes.
This work is focussed on the visualization of three-phase particle-laden liquid metal flow in model experiments, applying 2D X-ray and neutron transmission imaging. Low-melting gallium-based alloys are employed for the imaging studies at room temperature. Modell particles containing tungsten and gadolinium are used due to their excellent attenuation characteristics for polychromatic X-ray and thermal neutrons, respectively. Injection of inert argon gas drives the liquid metal flow in a rectangular shaped vessel having a gap size of up to 20 mm. For both X-ray and neutron imaging, the time-resolved measurements are performed by means of a scintillation screen in combination with a sCMOS camera. The captured trajectories of rising millimetre-sized gas bubbles and submillimetre-sized solid particles, carried by the bubbly liquid metal flow, are analysed regarding bubble - particle and particle - particle interactions.