Modern diffraction techniques for texture analysis

Automated Crystal Orientation Measurement (ACOM) enables individual grain orieritations to be determined with high speed and accuracy by interpreting backscatter or transmission Kikuchi patterns (SEM or TEM, respectively). The measurement of pole figures in the TEM is an alternative technique with deformed or extremely fine grained materials. In addition, deformation systems can be determined conveniently in the TEM with the assistance of an on-line computer program. Crystal orientation maps are obtained from, ACOM data by assigning colours to the image points, which are specific, e.g., for the grain orientation, the misorientation or the grain boundary character. The data sets are further used to calculate the Schmid factors of the individual grains, and, as a statistical average of texture over the sampled specimen area, the orientation distribution function and the misorientation distribution function. As a compliment to electron diffraction and conventional X-ray diffraction, an X-ray scanning apparatus has been developed for pole-figure measurement on selected small areas as well as for mapping the spatial distributions of crystal texture, residual lattice strain and element composition on bulk surfaces. The apparatus is based on energy dispersive X-ray diffraction. Spatial resolution of pole-figure measurement and residual lattice strain mapping is presently 0.1 mm, whilst resolution of texture and micro X-ray fluorescence element maps is about 0.05 mm. Residual lattice strain down to Deltaa/a = 4.10(-4) is analyzed by evaluating the shifts and profiles of diffraction peaks in the spectrum.