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X-ray Microdiffraction Characterization of Deformation Heterogeneities in BCC Crystals

Published online by Cambridge University Press:  01 February 2011

K. R. Magid
Affiliation:
Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, CA 94720, USA
E. T. Lilleodden
Affiliation:
Institut für Materialforschung II, Forschungszentrum Karlsruhe, D-76021 Karlsruhe, Germany.
N. Tamura
Affiliation:
Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA
J. N. Florando
Affiliation:
Engineering Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
D. H. Lassila
Affiliation:
Engineering Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
M. M. LeBlanc
Affiliation:
Engineering Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
R. I. Barabash
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN, USA
J. W. Morris Jr
Affiliation:
Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, CA 94720, USA
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Abstract

The deformation behavior of BCC metals is being investigated by x-ray microdiffraction measurements (μXRD) for the purpose of characterizing the dislocation structure that results from uniaxial compression experiments. The high brilliance synchrotron source at the Advanced Light Source (Lawrence Berkeley National Lab) and the micron resolution of the focusing optics allow for the mapping of Laue diffraction patterns across a sample. These measurements are then analyzed in order to map the distribution of residual stresses in the crystal. An important finding is the observation of Laue spot “streaking”, which indicates localized rotations in the lattice. These may represent an accumulation of same-sign dislocations. Theoretical modeling of the diffraction response for various slip systems is presented, and compared to experimental data. Preliminary results include orientation maps from a highly strained Ta bicrystal and a less highly strained Mo single crystal. The orientation maps of the bicrystal indicate a cell-like structure of dense dislocation walls. This deformation structure is consistent with previous OIM studies of the same crystal. The results suggest that μXRD may be a particularly useful tool for microscale studies of deformation patterns in a multi-scale investigation of the mechanisms of deformation that ranges from macroscopic deformation tests to high resolution TEM studies of dislocation structures.

Type
Research Article
Copyright
Copyright © Materials Research Society 2005

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References

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