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

Abstract

The basic processes of microstructure formation, e.g. plastic deformation, nucleation, and grain boundary movement are anisotropic. They depend on the crystallographic orientation of a considered grain as well as on the orientations of its neighbours with which it interacts. Hence, plastic deformation and recrystallization both give rise to the formation of textures, some of which have achieved considerable technological interest. The classical texture i.e. the orientation distribution function (ODF) of the crystallites does not distinguish individual grains, i.e. their sizes, shape and arrangement in the polycrystalline aggregate [1]. Hence, the classical texture is not sufficient in order to understand the formation mechanism of recrystallization textures, particularly the difficult interaction processes during dynamic recrystallization. In order to understand these processes it is necessary to know the complete orientation stereology as well as its changes with the time during recrystallization. The orientation stereology can be measured with the technique of orientation imaging microscopy [2,3]. This technique is well established and automated in the reflection scanning electron microscope. It yields, however, only a two-dimensional section of the function g(x) at the sample surface which has also been called orientation topology. It is not suited to measure the kinetics g(x,t) of the three-dimensional function during recrystallization processes, particularly not in the interior of the material.The six-dimensional orientation-location space must be imaged with the highest possible orientation-and location resolution. 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]. 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. 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].

Determination of the Orientation Relations between the Low- and High-Temperature Phases of NiS

“…In the present experiments, a single crystal of natural millerite from Wissen/Sieg (Germany) with a length of about 7 mm and a diameter of about 350 µm was clamped into a special holder and brought into a vacuum oven (Fig. 3) that was operated by a Lakeshore 340 controller at the beam-line BW5 at HASYLAB/DESY [17].…”

Oriented Grain Growth Analyses With In Situ Annealing Experiments Using High Energy Synchrotron Radiation

“…The measurements were performed from room temperature to 500 8C (below the local temperature minimum at which the eutectic and peritectoid mixture starts to crystallize from molten liquid solution) in a vacuum oven [11] (Figure 2), with a constant heating rate of 19.92 8C min À1 and a toggle angle of Dv ¼ 18, holding the last 3.95 min at 500 8C. Through the Bragg angle slits the 111 reflection was chosen, measuring at fixed orientation angles v ¼ {08, 328, 458, 708}.…”