Description of orientation coherence in polycrystalline materials

A multivariate grain size and orientation distribution function: derivation from electron backscatter diffraction data and applications

Grain size distribution and orientation distribution functions are combined in a single multivariate continuous grain size orientation distribution function (GSODF). Several examples of practical applications to low carbon steels are presented, in which it is shown how the GSODF can be used in the analysis of 2D and 3D electron backscatter diffraction data, and as input in full-field and mean-field crystal plasticity simulations.

Two of the microstructural parameters most influential in the properties of polycrystalline materials are grain size and crystallographic texture. Although both properties have been extensively studied and there are a wide range of analysis tools available, they are generally considered independently, without taking into account the possible correlations between them. However, there are reasons to assume that grain size and orientation are correlated microstructural state variables, as they are the result of single microstructural formation mechanisms occurring during material processing. In this work, the grain size distribution and orientation distribution functions are combined in a single multivariate grain size orientation distribution function (GSODF). In addition to the derivation of the function, several examples of practical applications to low carbon steels are presented, in which it is shown how the GSODF can be used in the analysis of 2D and 3D electron backscatter diffraction data, as well as in the generation of representative volume elements for full-field models and as input in simulations using mean-field methods.

Representation of grain misorientations (mesotexture) in Rodrigues-Frank space

Use of the Rodrigues vector R for representation of rotations in Rodrigues-Frank (RF) space is illustrated for the particular case of misorientations between grains in a cubic polycrystal. A subvolume of the fundamental zone of RF space is shown to be a convenient unit for the display of preferred misorientation, which here is referred to as ‘mesotexture’. When a misorientation sample population is displayed in the subvolume low angle, coincident axial direction and particularly coincident site lattice boundaries are presented with clarity thus allowing nature of the mesotexture to be assessed. Some features and properties of RF space are illustrated with reference to an experimental sample population of grain misorientations, and comparisons are made with other representation methods.