Texture (crystalline)

Sub-texture is understood in crystallography the totality of the orientations of the crystallites of a much crystalline solid.

From it, in particular, the anisotropy of the mechanical deformability of many metallic materials, an often -cited example of this is the earing during deep drawing of sheet metal, as well as the anisotropy of the magnetic properties of some soft magnetic (eg, grain-oriented dynamo sheet ) and hard magnetic materials (results for B. anisotropic Alnico magnets, samarium -cobalt alloys, anisotropic neodymium-iron- boron alloys, hard magnetic ferrites).

If the crystallites are distributed completely randomly, the material has isotropic properties, i.e., the same properties in all directions. In solidification processes often leads to a directed growth of the crystallites in the limit even for single crystallization. Also, by forming a material such as cold rolling or drawing textures are generated in hard magnetic materials powdered crystallites are oriented by magnetic fields during the sintering process. In deep-drawing steels the cubic crystal lattice is possible aligned so that a space diagonal direction of the cube shows in the rolling direction. Grain-oriented dynamo sheet has a misorientation angle of less than 3 ° a very sharp texture, named after its inventor Goss texture {110 } < 100 >. This shows the magnetic easy direction, a cube edge, in the rolling direction. A surface diagonal of the cube is in the transverse direction.

History

Although in the 19th century, the texture character of many rocks was known (eg when slate), learned their precise analysis a significant boost by the discovery of X-ray diffraction by Laue 1912. The film method allowed first the image of pole figures from which the preferred orientations (so-called ideal positions ) were estimated. By developing Zählrohrdetektoren and the use of neutron sources in research reactors, the pole figures could be determined much more accurately. Newer methods use 2D detectors, Synchrotron Much detectors - flight mass spectrometer and electron diffraction in scanning electron microscopes.

In the 1960s, the quantitative description of the texture by the so-called orientation density distribution function (ODF ) was developed.