Characterization of Growing Dendrites in CrMnFeCoNi High-Entropy Alloy by Time-Resolved and <i>In-Situ</i> Tomography
Keita Nakano, Taka Narumi, Kohei Morishita, Hideyuki Yasuda
Abstract
Time-resolved tomography (4D-CT) and X-ray diffraction (XRD) were combined to observe growing dendrites and to measure their crystallographic orientation in a CrMnFeCoNi high-entropy alloy with an FCC structure. The evolution of the dendritic grains cooling at 0.083 K/s was reconstructed using 200 projections over a 180° rotation every 4 s from 4D-CT and a phase field filter. The voxel size was a 6.5-µm cube. Simultaneously, the crystallographic orientations of the dendritic grains were measured by XRD. The dendrite arms grew preferentially along the 〈100〉 direction, corresponding with typical FCC alloys. The specific solid–liquid interfacial area, which was normalized by the total volume, was evaluated as a function of solid fraction. The interfacial area reached a maximum at a solid fraction of 0.55. The interfacial area was compatible with the reported values of Al–Cu and Mg–Sn alloys. The secondary arm spacing was on the same order of magnitude as the spacing of conventional alloys. Overall, it appears that solidification in this high-entropy alloy can be analyzed by using models developed for binary or pseudo-binary alloys.