X-Ray Tomographic Quantification of Diffusive Growth of Metallic Dendrite in High Magnetic Field

摘要

Suppressing the melt convection in the solidifying ingot is still considered to be a challenging task. By applying a high-magnetic field (HMF), we achieved a diffusive condition for the crystal growth. The atomic interdiffusion coefficient in the Al-Cu melt was measured in the HMF to define the critical magnetic flux density (MFD) for the diffusive crystal growth in the melt. A diffusive growth state was achieved in the melt when the MFD was greater than a critical 2.9 T. The influence of HMF on crystal growth was investigated by X-ray computed tomography. The HMF increased the size of crystal, but it decreased the crystal number and the curvature of dendrite tips as well as the specific surface area of dendrite. A transition of dendritic arms from seaweed to dendrite was observed after applying an HMF. Interface shape distribution maps showed that the HMF increased the proportion of ellipsoid shapes and decreased the proportion of hyperbolic shapes of solid-liquid interface. These were attributed to the decrease of constitutional supercooling caused by the magnetohydrodynamic effect. This work provides a new path to obtain a diffusive condition for crystal growth.

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