Texture and anisotropy of polycrystalline materials. Kiluchi diffraction patterns and orientation microscopy

Many technological materials and natural solids have a polycrystalline, or, at least, a partially crystalline structure. Their properties depend on both the structure of the polycrystalline aggregate and the properties of the individual crystals. The failure of a material is often caused by a heterogeneous microstructure and local defects, in which case knowledge of the overall texture is of very limited use. On the contrary, it is very useful to have high spatial resolution to determine local orientations, to know about orientation gradients within grains and disorientations between grains, and also to have access to some characteristic parameters of grain boundaries.

Developments in electron diffraction are detailed, with emphasis on current methods particularly relevant to texture analysis in materials science. Since 2000, numerous applications have been published in fields such as metallurgy and materials science, structural geology and biomineralization, which cannot be presented in detail in this article. Experimental set-ups are briefly discussed. Limitations due to spatial resolution and grain size are discussed. The crystal volume that contributes to a Kikuchi pattern is only 0.1 μm ³ . The preparation of clean, reasonably flat surfaces, free of foreign coatings, by metallographic polishing and ion milling is therefore particularly important, but often difficult.