Prof. Dr. Robert Schwarzer
D-71083 Herrenberg Germany
E-mail: mail at crystaltexture.com
Revised on 30 May 2018
The crystallographic texture of the solid, hereinafter briefly crystal texture or texture, is understood to mean the statistical entity of the crystallite orientations in a polycrystal. In the narrower sense, however, one often means the deviations from the statistical randomness of orientations, or in other words, the presence of preferred orientations. In bulk multi-crystalline materials, preferred orientations are in general regularly linked to the
process of structure
formation, such as solidification, nucleation, grain growth, recrystallization, phase transformation, sintering, plastic deformation. For powders, ceramic green compacts and sediments, preferred orientations often arise as a consequence of form anisotropy from (needle or platelet-shaped) crystallites in the starting material.
Texture analysis was originally based on the interpretation of pole figures, which in most cases were measured by X-ray diffraction. In further development, X-ray diffraction was supplemented by neutron diffraction for the highest relevance of the measurement and electron diffraction for highest spatial resolution. The measurement of pole figures is carried out by means of a texture goniometer. The texture goniometer makes it possible to adjust the Bragg
angle and thus
select the diffractive type of lattice planes (hkl), as well as to rotate the sample through the entire Ewald reference sphere, so that all directions of the sample can be brought into reflection position. A comprehensive account of the initial period until 1962 can be found in the German monograph "Texturen metallischer Werkstoffe (Textures of Metallic Materials)" by G. Wassermann and J. Grewen.
By using an X-ray Scanning Apparatus (XSA) or, recently, by individual grain orientation measurement in electron microscopes (e.g. EBSD and TKP), the information from texture analysis can be combined with the microstructure map of the material in real space to a comprehensive understanding known as Orientation Microscopy and finally Orientation Stereology. A promising future technique may be enabled by Ion Blocking Patterns (IBP) in the Ion Scanning Microscope.
This website crystaltexture.com provides a survey of the development of
• Pole figure measurement by selected area electron diffraction in the TEM (SAD)
• Individual grain orientation measurement by evaluating transmission Kikuchi patterns (TKP)
• Measurement and mapping of local texture with an X-Ray Scanning Apparatus (XSA)
• Outlook to orientation microscopy by using IBP.