In situ and real-time 3-D microtomography investigation of dendritic solidification in an Al–10 wt.% Cu alloy

Abstract

The microstructural evolution of an Al-10 wt.% Cu alloy was investigated during solidification at constant cooling rate by in situ synchrotron X-ray microtomography with a resolution of 2.8 lm. Solidification of this alloy leads to a coarse dendritic microstructure which was fully characterized in terms of variation with temperature of the solid fraction, the specific surface area of the solid-liquid interface and the local curvatures of the solid phase. By analysing the evolution with solid fraction of individual dendrites, at least two coarsening mechanisms were clearly identified in addition to solidification growth. The first mechanism involves remelting of small secondary dendrite arms to the benefit of bigger adjacent arms. The second is the coalescence of adjacent secondary arms, with progressive filling of the inter-arm spacing and coalescence at the tips. Although this mechanism preferentially occurs at high solid fractions, these results show that the evolution of the dendritic microstructure during solidification is complex and involves the occurrence of various mechanisms operating concurrently. In situ X-ray tomography thus allows revisiting the various models which have been proposed to account for dendrite coarsening during solidification.

X-Ray Videomicroscopy Studies of Eutectic Al-Si Solidification in Al-Si-Cu

“…Over the last decade, an increasing number of real-time X-ray imaging studies of solidification microstructures and phenomena in real metals have been reported, addressing a broad variety of topics such as dendritic growth, [20][21][22][23] coarsening, [24] morphological transitions, [23] dendrite fragmentation, [25][26][27] solute diffusion and convection, [22,28] and momentum transfer relations in eutectics [29] and monotectics. [30] Most of these, and other recent in-situ studies, have been carried out with high-brilliance synchrotron radiation, where X-ray absorption-and near-field phase contrast is combined to bring about 2-D or 3D time-resolved data.…”

“…[30] Most of these, and other recent in-situ studies, have been carried out with high-brilliance synchrotron radiation, where X-ray absorption-and near-field phase contrast is combined to bring about 2-D or 3D time-resolved data. [20][21][22][23][24][25][26][27]29,30] …”

Curvature of micropores in Al–Cu alloys: An X-ray tomography study

“…Nowadays, submicron resolution can easily be achieved on most synchrotron X-ray tomography beamlines. Combined with increasingly fast data acquisition systems, these techniques allow in situ microtomography observations of solidifying microstructures [14], even under tensile deformation [15].…”

Image reconstruction from sparse data in synchrotron-radiation-based microtomography

“…[6][7][8][9] In terms of microtomography, a thirdgeneration synchrotron radiation source provides partially coherent x-ray beam with enough brilliance to image a millimeter-sized sample at better than 10/micropixel resolution in a few seconds with high sensitivity. [10][11][12] In comparison to other nondestructive inspection techniques, such as magnetic resonance imaging, conventional micro-CT, and confocal microscopy, synchrotron-radiation-based micro-CT (SR-μCT) provides the unique capability of performing 3D dynamic studies. In SR-μCT, a synchrotron source can deliver intense x-rays over a wide energy spectrum, ranging from a few electrovolts to more than a hundred kiloelectrovolts.…”