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Bottom-up solidification of an NH4Cl-H2O alloy. This video, narrated by the late Prof. Angus Hellawell, shows the formation of channel segregation (freckles) in a transparent alloy. The movie has been digitized from the original film without further editing, which makes it rather large (60-75 Mb), so it may load slowly.
Bottom-up solidification of a Ga-25wt%In alloy: Dendrite growth and segregation freckle formation under the condition of solutal convection. (cooling rate 0.1 K/s, temperature gradient 1.5-2 K/mm)
This movie, produced by Natalia Shevchenko, Stephan Boden and Sven Eckert, were obtained by in-situ X-ray video microscopy carried out using a microfocus X-ray tube (XS225D, Phoenix|X-ray). For further information, please email to: s.eckert_at_hzdr.de
Bottom-up solidification of a Ga-25wt%In alloy: The solutal convection is suppressed by an imposed magnetical field in the time period 800s -1800s. Adjacent to the solidification front the forced melt flow is in horizontal direction. (see also S. Boden, S. Eckert and G. Gerbeth, Materials Letters 64(2010), 1340) (cooling rate 0.1 K/s, temperature gradient 1.5-2 K/mm)
This movie, produced by Natalia Shevchenko, Stephan Boden and Sven Eckert, were obtained by in-situ X-ray video microscopy carried out using a microfocus X-ray tube (XS225D, Phoenix|X-ray). For further information, please email to: s.eckert_at_hzdr.de
Alpha-Al and fibrous Al-Si eutectic growth in the presence of fluid flow from directional solidification parallel to gravity in a Al-9wt%Si-15wt%Cu-0.015wt%Sr alloy. Imposed temperature gradient of 45 K/mm, and sample velocity of 6.3 microns/s
This movie, produced by Ragnvald Mathiesen and Lars Arnberg, was obtained by in-situ X-ray video microscopy carried out at the ESRF in Grenoble, France at beam lines ID22 and ID6. For further information, please email to: Ragnvald.Mathiesen@ntnu.no
This movie is derived from a cellular automaton - finite element simulation performed by collaborators at MINES ParisTech CEMEF.
Simulation of solidification of a Sn-3%Pb alloy with no grain refiner in a 10 cm width, 6 cm height, 1 cm thick rectangular cavity. All sides are insulated, except the left and right narrow vertical faces, which are cooled at constant rate while maintaining a constant temperature difference. The movie shows the fluid flow (arrows represent the liquid velocity) and isotherms (mostly horizontal surfaces shown up to the time when solidification starts). The grain structure is modeled using a Cellular Automaton (CA) method to track the nucleation and growth of the envelope of each individual dendritic grain. Coupling of the CA to the Finite Element (FE) solution of the heat, fluid and solute flows permits prediction of the interaction between the solid grain structure and the liquid. The CAFE model predicts macrosegregation due to washing of the fluid from the mushy zone, which is enriched in Pb due to rejection of Pb during solidification of the primary phase. The simulation also shows how the flow modifies the orientation of the columnar grain structure. Toward the end of solidification, some new grains nucleate and grow in the liquid as an equiaxed structure [T. Carozzani, Ch.-A. Gandin, H. Digonnet, M. Bellet, K. Zaidat and Y. Fautrelle, Metall and Mat Trans A 44:873-887, 2013]
This video shows a 3D simulation of the formation of segregated channels within the mushy zone during directional solidification of a hypoeutectic In-75%wt Ga alloy: The In-rich solid forming in the bottom rejects Ga, resulting in localized lower regions of lower liquidus temperature (shown in magenta). The undercooled liquid is therefore enriched with lighter Ga. The consequence is thermo-solutal convection (unstable segregation plumes) rising from the liquid pools upward into the free liquid, where the solute is redistributed causing positive macrosegregation (parallel isosurfaces of concentration at the end) . The corresponding experimental configuration is presented in Shevchenko et al., Metallurgical and Materials Transactions 44A (2013) 3797.