Turbulent breakup of non-metallic inclusions and equiaxed crystals during solidification of a hypoeutectic al-si alloy

Abstract The breakup of agglomerates and bodies suspended in turbulent flows are important phenomena that influence many aspects of modern solidification processing. It is often assumed that breakup operates in high-pressure die casting, wherein molten metal is transported at high speed through a narrow orifice system. To test this assumption, X-ray tomography and electron backscatter diffraction mapping are used to characterise pores, inclusions, and primary α-Al grains in die-cast samples produced with different flow field intensities. Numerical simulations are performed in ProCAST (ESI Group) to quantify the three-dimensional flow fields and to relate the derived quantities to breakage. Increasing the dissipation rate of turbulent kinetic energy is shown to induce a refinement of both non-metallic inclusions and primary α-Al1 grains nucleated in the shot chamber, a phenomenon which is ascribed to breakage. Several breakup mechanisms are discussed, with emphasis on the role of fluid turbulence.