New concepts of texture ananlysis and their contirbution to our understanding of materials properties

摘要

The texture of a polycrystalline material, in the classical sense, is defined by the orientation distribution function f(g) of the crystallites irrespective of their local arrangement. The new concept of texture considers crystal orientation g(x) as a function of location x in the material. Additionally, also the substructure (lattice defects) may be considered as a function s(x) of location. Several integrals over the aggregate function called generalized textural quantities have also been used. The classical texture function f(g) can be obtained from pole figures measured with a texture goniometer and followed by mathematical pole figure inversion. More advanced experimental equipment uses one-dimensional position sensitive detectors, area detectors, parallel beam technique or location resolved texture measurement. The greatest step forward was, however, achieved by automated orientation-location scanning on the basis of Kikuchi diagrams. This technique yields a two-dimensional section of the aggregate function g(x). Model calculations of physical properties of polycrystalline materials show that the classical texture f(g) defines only the Voigt and Reuss bounds which deviate up to 25percent from each other. In order to reach a higher accuracy the aggregate function g(x) must be used. This can be done in terms of the "Cluster Model" containing approx 1000 crystals. Using this model it was shown that grain shape, grain packing, and orientation correlation have a definite influence on the properties of polycrystals. By particular choices of g(x) the whole range between the Voigt-Reuss bounds can be reached.