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Quantitative texture analysis in the Texture plugin of SmartLab Studio II

Summer 2019, Volume 35, No. 2
01-07
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Keigo Nagao and Akito Sasaki

The presence of crystallographic texture (preferred orientation) in polycrystalline materials has a significant effect on the anisotropy of the properties of these materials. That means that quantitative description of the orientation distribution of crystallites, or the orientation distribution function (ODF), is an important task for materials characterization and prediction of their properties. Direct measurement of the ODF is not possible; instead, pole figures (PF) can be measured to determination the ODF. Reconstruction of the ODF from measured PFs is a main goal of quantitative texture analysis. Thus, two problems should be solved to obtain an ODF: measurement and processing of experimental PFs and ODF reconstruction from PFs.

In the X-ray diffraction technique, there are two basic modes for PFs measurement: the conventional mode with a 0D detector and a more advanced mode using a 2D detector(1). While measurement of PFs with 2D detectors is more advanced, it requires additional tools for conversion of the detector’s data into PFs.

When the PFs are prepared, it is possible to start the ODF reconstruction process. Currently, three methods are used for ODF reconstruction: the series expansion method(3), the component method, and direct methods like WIMV or ADC. Each method has advantages and disadvantages. The series expansion method is more general, but it requires a large number of measured PFs and has some problems with numerical calculations. The components method represents the ODF as a set of model functions (components) that have clear physical meaning. This method is most convenient for interpretation and representation of the results, but can require a lot of time for selection of components and fitting their parameters. Direct methods use a numerical calculation of the ODF on a discrete grid in rotation space. They are the most simple and convenient to use but do not provide an interpretation of the ODF.

In the next sections we will describe the Texture plugin of SmartLab Studio II, which is intended for data processing and quantitative texture analysis. This plugin implements two of the above-mentioned methods of ODF reconstruction: WIMV and the components methods. Both can be used for all types of crystal systems and two types of sample symmetry—triclinic and orthorhombic. Also, the plugin can use three of the most popular definitions of Eulerian angles in the texture community: Bunge notation (φ1,Φ,φ2), Roe notation (Ψ,Θ,Φ) and Matthiers notation (α, β, γ). Roe and Matthiers notation are physically equivalent, with the only difference being the letters used in the notation.

 

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