Materials Science Research Lecture
***Refreshments at 3:45pm in Noyes lobby
Abstract:
Most crystalline materials are composed of many small crystallites or grains that have lattices of different orientations. The boundaries between the grains can move to reduce the total grain boundary energy of the ensemble thus altering the properties of the material. To predict the evolution of these grain structures, it was thought that only the grain boundary's energy and mobility are needed. However, by comparing the evolution of experimentally determined three-dimensional grain structures to those derived from simulation we find that the grain boundary mobilities are largely independent of the misorientation of the grains and the inclination of the grain boundary, contradicting the classical view of grain growth. The results of the experiments will be discussed. To further analyze this large dataset, we propose a modification to an orientation field model for grain growth wherein the coefficients of the free-energy functional become functions of the misorientation between the grains, which is a non-local quantity. Due to this modification, an arbitrary dependence of the grain boundary free energy on the misorientation can be embedded in the model. The capabilities of the model are demonstrated by the ability to compute the evolution of grains where there is a sharp cusp in the misorientation dependent grain boundary free energy.
More about the Speaker:
Peter Voorhees is the Frank C. Engelhart Professor Emeritus of Materials Science and Engineering at Northwestern University and a Faculty Associate at California Institute of Technology. He received his Ph.D. in Materials Engineering from Rensselaer Polytechnic Institute and was a member of the Metallurgy Division at the National Institute for Standards and Technology until joining the Department of Materials Science and Engineering at Northwestern University. He has received numerous awards including the TMS Bruce Chalmers and Leadership Awards, the ASM J. Willard Gibbs Phase Equilibria Award, Moore Distinguished Scholar, and the McCormick School of Engineering and Applied Science Award for Teaching Excellence. Professor Voorhees is a fellow of ASM International, the Minerals, Metals and Materials Society, and the American Physical Society. He is a member of the American Academy of Arts and Sciences. Professor Voorhees was Chair of the Materials Science and Engineering Department for a decade and was a founding Director of the Northwestern Argonne Institute for Science and Engineering, and the Center for Hierarchical Materials Design.