Automated tracking of boundary shapes and motions in response to thermal and/or mechanical excitation is essential to studies of coarsening phenomena, phase transitions, and numerous other dynamical problems. In the context of our studies of microstructure coarsening, we have developed tools for optimized motion tracking and curvature estimation that obviate the need for constructing a mesh. A linear optimization procedure estimates motion in three dimensions of a boundary defined in an initial state by N points and in a final state by M points. Triple lines and quadruple points serve as edge constraints. A procedure that performs least squares fits of subsets of boundary points to an ellipsoidal surface leads to estimates of local curvature. These boundary characterizations are now being applied to our unique High Energy Diffraction Microscopy data sets (and complimentary data from Oak Ridge National Laboratory researchers) that characterize annealing responses of Nickel, Copper and Aluminum microstructures in three dimensions. The combination of curvature and motion estimation will allow rigorous testing of curvature based theories of such motions.

(A) (B)

(A) Illustration of automated boundary tracking including an event in which one boundary disappears and another appears. The sketch below illustrates the topological change that has been correctly tracked. Numbers enumerate the grains involved in this two dimensional example.

(B) Fit of a quadratic surface in 3D to points approximating a boundary. Local curvatures are obtained from fit parameters. Combined tracking of motion and curvature will be used to test theories of coarsening in three dimensional polycrystals.

Grain Boundary Characterization for Coarsening Studies

Robert M. Suter, Carnegie-Mellon University, DMR 1105173

Broadening participation of underrepresented groups• Supported research projects by CMU

undergraduates Nastassia Barber and Jose Salazar Espitia.

Development of infrastructure:• NSF supported development of near-field

HEDM is having broad impact in the materials science and engineering communities. A multi-institutional project (AFRL, APS, LLNL, CMU) is developing sophisticated sample treatment apparatus, data collection macros, and analysis software for combined grain orientation, elastic strain, and density contrast.

• Computer codes for boundary and boundary motion characterization will be made available for use by scientists working on many other problems involving such motions.

• Participation in Dream.3D development: this open source microstructure analysis project brings together a wide variety of codes for application to 3D data sets. We have assisted in developing a reader for our data so that we and others can take advantage of on-going analysis developments.

Undergraduate students correlated HEDM diffraction spots (detector image above left) with appropriate crystal structure indices to test completeness of the model structure used to reconstruct 1 mm3 of AlON (above right) for the Army Research Laboratory.

Grain Boundary Characterization for Coarsening Studies

Robert M. Suter, Carnegie-Mellon University, DMR 1105173

Experimental hutch at the 1-ID beam line of the Advanced Photon Source showing apparatus for combined near- and far-field HEDM measurements.

Far-field detector (strain sensitivity)

Near-field and mechanical loading.