When 3:30 PM - 5:00 PM Oct 28, 2011
Where 1670 CSE
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Elizabeth Holm, Computational Materials Science and Engineering Department, Sandia National Laboratories


Grain Boundary Myth Busters: A survey of grain boundary motion mechanisms

Recent advances in materials modeling and experiment have allowed us to re-examine some of our fundamental assumptions about materials structure and properties. Atomistic simulations, in particular, permit observation of grain boundary phenomena on time and length scales inaccessible by experiment. When combined with high-throughput methods, such simulations can characterize a broad spectrum of structures, sufficient for surveying global behaviors and trends.

 

When we analyze the results of high-throughput atomistic simulations of grain boundary mobility, we discover that many of our assumptions – dating back to the 1940’s – are wrong. In fact, grain boundary motion is far more complicated than the textbook premise that grain boundaries move by a thermally activated process. Instead, we find four different classes of grain boundary motion divided into fifteen distinct trends, most of which have not been previously reported or characterized in detail.

 

Some of these trends are surprising and counterintuitive. For example, a substantial minority of the boundaries surveyed undergo nonactivated motion, where boundary mobility actually increases when temperature decreases. We are just beginning to understand how these newly identified motion trends can affect microstructural evolution in polycrystalline materials. Some examples of the influence of novel boundary motion on grain growth in conventional and nanocrystalline materials will be presented.

 

 

This work was performed at Sandia National Laboratories, a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.