KOSSEL-TECHNIQUE BY MEANS OF SYNCHROTRON BEAM EXCITATION - A NEW METHOD FOR MATERIAL CHARACTERIZATION. Hans-Jürgen Ullrich, Jürgen Bauch, Ralph Röder, TU Dresden, Institut für Werkstoffwissenschaft, Mommsenstr. 13, D-01062 Dresden

The first KOSSEL experiments using synchrotron radiation were performed in 1992. The exposure time was drastically reduced due to the high intensity of polychromatic synchrotron radiation at HASYLAB. When using imaging plates, serveral seconds of exposure times are sufficient. When using X-ray films, the required time increases to the few minutes. KOSSEL patterns of crisp contrast could be obtained from elements, alloys, intermetallics, semiconductor compounds and minerals.The following problems received special attention:

*Proof of minor tetragonal distortions (c/a >= 1,02) in FeAl cylindrical specimen, as a function of their position in the material, determination of the value of the distortions.

*Lattice defect and texture analysis of transformer sheets. The advantage of the new method is, that the excitation depths of the X-rays for the KOSSEL patterns are extended through the entire sample thickness. Therefore, KOSSEL lines are produced at the front and rear surface of the sheet. In the case of synchrotron radiation, the pattern from the rear side of the sample are easier to compare with those of the front side in a single measurement process.

Synchrotron excited KOSSEL techniques provide a wide range of new, advantageous applications, as compared with other X-ray diffraction technique:

*Precision determination of the lattice constants in microvolumina with high accuracy ([[emptyset]]a/a = 10^-4 ...10^-5)

*Precision determination of lattice spacings d_hkl of each individual net plane (hkl), with high accuracy in the analysis of residual stresses (especially the character and orientation) of the tensor of stress in a single grain

*Determination of the orientation of neighboured, crystalline grains visual in the microscope and subgrains with high precision (tilt angle < 0,1deg.)

*Determination of tetragonal distortions of cubic lattices

*Phase identification in microvolumina by means of the topology of KOSSEL lines (qualitative phase analysis)

*In situ observation of phase transformations in environmental devices

*Measurement of the phase differences of scattered X-ray waves of polar net planes

We thank the HASYLAB staff for technical help and the Deutschen Forschungsgemeinschaft (DFG registration number UI 138/1-1 ) for financial support.