Grants and Contracts Details
Description
~Ietals are usually polycrystalline: they are aggregates of tiny grains of yarious orientations.
sizes, and shapes. The orientations of the grains and their stereology (i.e.. how the!'
arc arranged in space) constitute the meso-scale structure of a polycrystal. On a finer scale,
the grains themselves also haye microstructures (e.g.. distributions of dislocations). Together
with chemical composition, the meso- and micro-scale structures of a metal determine its
macroscopic mechanical properties, including its formability.
The technology of Field Emission Gun Scanning Electron '.Iicroscope \,it h Electron
Backscatter Diffraction (FEGSE~I-EBSD) has made enormous advances recently. \Vith
the state-of-the-art FEGSElIl-EBSD equipment. we contend that not only the meso-scale
structure but also the dislocation tensor of a polycrystal1ine metal can be determined, thus
opening up n('\\' forefronts of research with broad impact.
This proposed project comprises three preliminary jexploratory studies. with a yiew to
the deyelopment of three ful1-ftedged research programs with objectiyes as fol1ows:
. to design a protocol for recO\'ery of the dislocation tensor of a polyerystal1ine sample
through EBSD measurement of the lattice curyature in its grains;
. to deyelop a theory for recO\'ery of the dislocation tensor through ultrasonic measurernents:
. to deyise a plastic potential that includes the dislocation tensor as an independent Yariable
and would adequately model the behm'ior of continuous-cast .5000 series aluminum
alloys in met al forming operations.
The first program is central to a subject of great interest to many in the materials science
community. The second should be of interest to the community in nondestructive evaluation.
where applications of ultrasound in characterization of material microstructures haye become
a hot theme. The third further deyelops joint research projects of the PI with colleagues
at the Uniyersity of Kentucky, which are supported by AFOSR and 0JSF. Commonwealth
Aluminum Concast. Inc. (CACI) is the industrial partner of one of the projects.
Key Words: multiscale modeling: orientation imaging microscop!': geometrically
necessary dislocations; nltrasonic measurement of dislocations: plastic potential.
Status | Finished |
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Effective start/end date | 5/1/05 → 12/31/06 |
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