Ostwald ripening of faceted Si particles in an Al-Si-Cu melt

The microstructural evolution of an Al-Si-Cu alloy during Ostwald ripening is imaged via synchrotron-based, four-dimensional (i.e., space and time resolved) X-ray tomography. Samples of composition Al-32wt%Si-15wt%Cu were annealed isothermally at 650°C, in the two-phase solid-liquid regime, while to...

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Bibliographic Details
Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2016-09, Vol.673 (C), p.307-320
Main Authors: Shahani, A.J., Xiao, X., Skinner, K., Peters, M., Voorhees, P.W.
Format: Article
Language:English
Subjects:
4D materials science
Aluminum-silicon-copper alloys
Coarsening
Computer simulation
Facets
MATERIALS SCIENCE
Mathematical models
Microstructure
Ostwald ripening
Phase transformations
Reconstruction
Silicon
Synchrotron-based X-ray tomography
Ternary systems
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Summary:The microstructural evolution of an Al-Si-Cu alloy during Ostwald ripening is imaged via synchrotron-based, four-dimensional (i.e., space and time resolved) X-ray tomography. Samples of composition Al-32wt%Si-15wt%Cu were annealed isothermally at 650°C, in the two-phase solid-liquid regime, while tomographic projections were collected in situ over the course of five hours. Advances in experimental methods and computational approaches enable us to characterize the local interfacial curvatures and velocities during ripening. The sequence of three-dimensional reconstructions and interfacial shape distributions shows highly faceted Si particles in a copper-enriched liquid, that become increasingly isotropic or rounded over time. In addition, we find that the coarsening rate constant is approximately the same in the binary and ternary systems. By coupling these experimental measurements with CALPHAD modeling and ab initio molecular dynamics simulation, we assess the influence of Cu on the coarsening process. Finally, we find the unusual “pinning” of microstructure at the junction between rough and smooth interfaces and suggest a mechanism for this behavior.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2016.06.077