When   Friday, May 1, 2009   Time   2:00 PM - 3:00 PM  
Where   Technological Institute M 416 2145 Sheridan Rd.   map it
Audience   - Faculty/Staff - Student - Public
Contact   Molly E Scanlon   +1 847 491 5586  
Group   McCormick-Colloquia Engineering Sciences and Applied Mathematics

Applied Math Colloquium

Title: Self-Similar Pinch-Off of Liquid Tubes in Dendritic Aluminum-Copper During Coarsening

Speaker: Larry Aagesen, Northwestern University

Abstract:

Dendrites frequently form during the solidification of metallic alloys in technologically important processes such as casting and directional solidification. The resulting microstructures are highly interconnected mixtures of two or more phases of different atomic compositions. During coarsening, the process of the system reducing its total interfacial area to lower its energy, tubes connecting regions of one phase can pinch off due to Rayleigh instabilities. These topological singularities can be characterized as self-similar, with a shape that is time-invariant when scaled by the appropriate dimensional factor. This process has recently been observed in-situ in aluminum-15 weight % copper using X-ray tomography during coarsening at high temperature. The time dependence of the pinching events and shapes of the tubes are compared to theoretical predictions from the self-similarity analysis and to simulation results from a phase-field model. This approach is expected to be applicable to a broad variety of systems when coarsening is driven by diffusion in the tubes or in the surrounding matrix phase.

Special Note: This talk is part of the RTG Seminar series.