Texture and microstructure imaging in six dimensions with high-energy synchrotron radiation

Abstract

The texture of a material can be calculated from several pole ®gures, which, in turn, are usually measured by one of several`step-scan' techniques. In these techniques, the ®nite step width limits the attainable orientation resolving power. In the present paper, the discontinuous step-scan technique is replaced by a continuous`sweeping' technique based on the continuous movement of an area detector during exposure. In this way, continuous two-dimensional`images' of pole ®gures are obtained, without the necessity of interpolation. Similar sweeping techniques are also being used to obtain continuous images of other sections and projections of the six-dimensional`orientation±location' space which characterizes a polycrystalline structure completely. The high potential orientation and/or location resolving power of these imaging techniques can only be reached with synchrotron radiation. In the present paper, the measurements were made at the high-energy (short-wavelength) beamline BW5 at HASYLAB/DESY in Hamburg. The high orientation and location resolving power implies the necessity to distinguish`grain-resolved' textures and microstructures (mainly in recrystallized materials) from`continuous' ones (mainly in deformed materials). Under certain conditions, it is thus possible to obtain the complete six-dimensional`orientation stereology' of grain-resolved microstructures. The new methods are illustrated with several examples, including technological applications.

High‐Resolution Imaging of Texture and Microstructure by the Moving Detector Method

“…This allows to separate the orientation dependences of nucleation and grain growth during the whole recrystallization process (to be published elsewhere). Figure 14 shows the (200) pole figure of an Al-sample hot rolled 62% at 490-460 C. The texture is similar to the recrystallization texture of nickel as shown by Bunge et al (2003a), i.e. it is essentially the cube texture.…”

“…However, they determine the imaging scale in this direction onto the detector. In order to reach a good scaling factor and hence a good location resolution the scanning range in y-direction must be adapted to the detector diameter in y-direction (Bunge et al, 2003a).…”

Measurement of High-Resolution Recrystallization Textures in Nickel Sheets Using High-Energy Synchrotron Radiation

“…This can be done by location-resolved diffraction of highenergy synchrotron radiation [4,5,6]. In order to fully exploit the high resolving power of this radiation, the conventional step-scan technique had to be replaced by a continuous "sweeping" technique with a moving detector [5,6,7].…”

“…During exposure the detector is being shifted continuously while, at the same time, the sample is being rotated or translated, continuously, too. This technique allows to measure different types of two-dimensional images which are sections and projections of the sixdimensional orientation-location space [5,6,7]. …”

“…In order to fully exploit the high resolving power of this radiation, the conventional step-scan technique had to be replaced by a continuous "sweeping" technique with a moving detector [5,6,7]. For this purpose either a diffraction angle slit or a diffraction plane slit was introduced additionally between sample and detector in the diffractometer at the high-energy beam-line BW5 at HASYLAB [6,7]. During exposure the detector is being shifted continuously while, at the same time, the sample is being rotated or translated, continuously, too.…”