A fast and non-destructive method for generating three-dimensional maps of the grain boundaries in undeformed polycrystals is presented. The method relies on tracking of micro-focused high-energy X-rays. It is veri®ed by comparing an electron microscopy map of the orientations on the 2.5 Â 2.5 mm surface of an aluminium polycrystal with tracking data produced at the 3DXRD microscope at the European Synchrotron Radiation Facility. The average difference in grain boundary position between the two techniques is 26 mm, comparable with the spatial resolution of the 3DXRD microscope. As another extension of the tracking concept, algorithms for determining the stress state of the individual grains are derived. As a case study, 3DXRD results are presented for the tensile deformation of a copper specimen. The strain tensor for one embedded grain is determined as a function of load. The accuracy on the strain is Á4 9 10 À4 .

We observed the in situ growth of a grain during recrystallization in the bulk of a deformed sample. We used the three-dimensional x-ray diffraction microscope located at the European Synchrotron Radiation Facility in Grenoble, France. The results showed a very heterogeneous growth pattern, contradicting the classical assumption of smooth and spherical growth of new grains during recrystallization. This type of in situ bulk measurement opens up the possibility of obtaining experimental data on scientific topics that before could only be analyzed theoretically on the basis of the statistical characterization of microstructures. For recrystallization, the in situ method includes direct measurements of nucleation and boundary migration through a deformed matrix.

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Metals. -The in situ growth of a grain during recrystallization in the bulk of a deformed sample of Al of commercial purity is observed using a three-dimensional X-ray diffraction microscope. The results show a very heterogeneous growth pattern, contradicting the classical assumption of smooth and spherical growth of new grains during recrystallization. The in situ bulk measurements open up the possibility of obtaining experimental data on topics that previously could only be analyzed theoretically on the basis of the statistical characterization of microstructures. -(SCHMIDT*, S.; NIELSEN, S. F.; GUNDLACH, C.; MARGULIES, L.; HUANG, X.; JENSEN, D.