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Texture and pole figures

Texture and pole figures

Distribution of crystallographic orientations

In many cases, crystallographic texture (preferred orientation) can be introduced into a material during the fabrication process. For example, when steel sheets are rolled in the manufacturing process, a sheet texture is often produced. Since texture can affect a material's properties by introducing structural anisotropy, it is desirable to measure a material's texture.

The typical measurement to determine texture is called a pole figure. Traditional pole figure measurements are made by recording the intensity of a given Bragg reflection as a function of rotation and tilt of the sample. In an in-plane pole figure, the incident beam, sample rotation, and detector angle are all moved, eliminating the necessity to tilt the sample. The in-plane pole figure also allows a greater range of texture to be recorded, as it now contains the in-plane (sample surface) texture of the sample.

The top two diagrams (at right) show an in-plane pole figure of the reflection for a rolled steel sheet sample. The central dark red portion indicates texture along the [211] direction. The figure shows the pole figure in both in stereographic projection (contour map) and 3D display. The bottom two diagrams (at right)show the (002) pole figure of a 50 micron thick Cu foil. The strong (002) peak at the center of the pole figure indicates that the foil is preferably (001)-oriented along the surface normal. The four peaks seen at the rim are Cu (200), (200), (020), and (020), respectively, due to the cubic structure of the copper lattices.