期刊
ACTA MATERIALIA
卷 146, 期 -, 页码 176-186出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2017.12.056
关键词
Dendritic solidification; Microstructure; Coarsening; Sidearm detachment; X-ray radiography; Phase-field model; Material properties
资金
- German Helmholtz Association
- NASA [NNX14AD69G]
- NASA [685543, NNX14AD69G] Funding Source: Federal RePORTER
The local dynamics of dendritic sidearms during coarsening are studied by combining in-situ radiography observations with numerical and analytical models. A flat sample of a Ga-In alloy is partially solidified and then held isothermally in a vertical temperature gradient. The evolving dendritic microstructure is visualized using synchrotron X-ray imaging at the BM20 (ROBL) beamline at ESRF, France. During the coarsening stage, the temporal evolution of the geometrical features of sidebranches is captured by automated image processing. This data is then used to quantify the dynamics of two basic evolution mechanisms for sidebranches: retraction and pinch-off. The universal dynamics of sidearm necks during pinch-off are exploited to determine the product of liquid diffusivity and capillarity length Dd(0), as a parameter that is crucial in the calibration of quantitative models. By employing an idealized phase-field model for the evolution of a single sidebranch, the behavior of selected sidebranches is reproduced from the experiments in a consistent way. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. AU rights reserved.
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