When 10:30 AM - 11:30 AM Sep 18, 2015
Where 1571 GG Brown
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Quantifying Grain Boundary Properties and Their Distributions Using Three-Dimensional Data

Greg Rohrer
Carnegie Mellon University, Department of Materials Science and Engineering

Grain boundaries in polycrystalline materials have an inherent complexity – each boundary is differentiated by five macroscopic parameters and they form a connected network within the material. Until recently, it was common to consider only the average properties (such as energy or mobility) of grain boundaries. This was because it was nearly impossible to study representative populations of boundaries and determine their properties. However, the automated control of electron microscopes has opened up new possibilities for the acquisition of large amounts of data. Automated serial sectioning using a focused ion beam, coupled with orientation measurements by electron backscatter diffraction, makes it possible to record volumes of data that represent the full diversity of grain boundary types. By measuring the distributions of grain boundary properties, we are beginning to understand linkages between them (such as population, energy, and curvature) and how the distributions are related in different materials. In this seminar, I will present and compare results obtained by serial sectioning using Ga- and Xe- focused ion beam instruments (the later being as much as 50 times faster than the former). From these results, we have found correlations between grain boundary population distributions and grain boundary energy distributions. We have also found strong correlations among the distributions for materials with the same crystal structure. The implications of these results for predicting microstructure evolution in metals and ceramics will be discussed.

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