An alignment algorithm using coherent twin boundaries as internal reference in 3D‐EBSD.

A three‐dimensional (3D) microstructural volume is reconstructed from a stack of two‐dimensional sections which was obtained by serial sectioning coupled with electron back scattering diffraction (EBSD) mapping of a 316L austenitic stainless steel. A new alignment algorithm named linear translation by minimising the indicator (LTMI) is proposed to reduce the translational misalignments between adjacent sections by referencing to coherent twin boundaries which are flat and lying on {111} planes. The angular difference between the measured orientation of a flat twin boundary and that of the {111} plane is used as an indicator of the accuracy of the alignment operations. This indicator is minimised through linear translations of the centroids of triangular facets, which constitute grain boundaries at a distance not restricted by the in‐plane step size of the EBSD maps. And hence the systematic trend in the translational misalignments can be effectively reduced. The LTMI alignment procedure proposed herein effectively corrects the misalignments remained by other methods on a 3D‐EBSD data prepared using serial sectioning methods. The accuracy in distinguishing between coherent and incoherent twin boundaries is significantly improved. LAY DESCRIPTION: Accurately reconstructing the three‐dimensional (3D) microscopic structure of metal materials is crucial for exploring the relationship between the structure and properties of materials. Researchers utilise electron backscatter diffraction (EBSD) technique to sequentially acquire two‐dimensional (2D) images layer by layer, which are then stacked to reconstruct the three‐dimensional (3D) microstructure of the material. However, misalignments during this stacking process can result in an incorrect alignment between the layers, leading to distortion of the entire 3D volume. Previous methods aligned layers by making adjacent layers as similar as possible, but this could introduce cumulative errors. This work has proposed a new alignment method, 'Linear translation by minimising the indicator' (LTMI), which utilises coherent twin boundaries as additional references to guide the stacking process and accurately find the correct position between layers. Coherent twin boundaries serve as references because of their characteristics: these boundaries are special structures within the material, having a flat morphology and lying on specific crystal planes. Layers are shifted repeatedly until all the coherent twin boundaries in the sample display these characteristics, signifying that the layers are properly aligned. The LTMI method offers a way to significantly enhance the accuracy of 3D microstructural analysis, which is essential for designing materials that are strong and durable, with profound implications for the materials field. [ABSTRACT FROM AUTHOR]