Papers by Keyword: 3D-EBSD

Abstract: A focused ion beam (FIB) coupled with high resolution electron backscatter diffraction (EBSD) has emerged as a useful tool for generating crystallographic information in reasonably large volumes of microstructure. In principle, data generation is reasonably straightforward whereby the FIB is used as a high precision serial sectioning device for generating consecutive milled surfaces suitable for mapping by EBSD. The successive EBSD maps generated by serial sectioning are combined using various post-processing methods to generate crystallographic volumes of the microstructure. This paper provides an overview of the use of 3D-EBSD in the study of various phenomena associated with thermomechanical processing of both crystalline and semi-crystalline alloys and includes investigations on the crystallographic nature of microbands, void formation at particles, phase redistribution during plastic forming, and nucleation of recrystallization within various regions of the deformation microstructure.

Abstract: A focused ion beam (FIB) coupled with high resolution electron backscatter diffraction (EBSD) has emerged as a useful tool for generating crystallographic information in reasonably large volumes of microstructure. In principle, data generation is reasonably straightforward whereby the FIB is used as a high precision serial sectioning device for generating consecutive milled surfaces suitable for mapping by EBSD. However, there are several challenges facing the technique including the need for accurate reconstruction of the EBSD slice data and the development of methods for representing the myriad microstructural features of interest including, for example, orientation gradients arising from plastic deformation through to the structure of grains and their interfaces in both single-phase and multi-phase materials. This paper provides an overview of the use of 3D-EBSD in the study of texture development in alloys during deformation and annealing and includes an update on current research on the crystallographic nature of microbands in some body centred and face centred cubic alloys and the nucleation and growth of grains in an extra low carbon steel.

Abstract: We report the recent development of a 3D orientation data post-processing software, which we refer to as QUBE. Amongst other functionalities, it offers the possibility to specify the spatial and orientational distribution of boundary normals. We describe a method to reconstruct a voxel-accurate and smooth 3D boundary triangle mesh by algorithmic means. A proof of concept is given by a benchmark on a generic dataset and we demonstrate a first result with the description of selected grain boundaries in an Fe-28%Ni sample.

Abstract: This study highlites deformation behavior of austenitic and pearlitic steels by in-situ neutron diffraction and 3D/4D EBSD measurement with a particular attention to their hierarchy.In particular stress partitioning in these microstructures is examined from macroscopic as well as microscopic scale length levels, and they are correlated to each other.

Abstract: Obtaining knowledge on the grain boundary topology in three dimensions is of great importance as it controls the mechanical properties of polycrystalline materials. In this study, the three dimensional texture and grain topology of as-deformed ultra fine grained Cu-0.17wt%Zr have been investigated using three-dimensional orientation microscopy (3D electron backscattering diffraction, EBSD) measurements in ultra fine grained Cu-0.17wt%Zr. Equal channel angular pressing was used to produce the ultra fine grained structure. The experiments were conducted using a dual-beam system for 3D-EBSD. The approach is realized by a combination of a focused ion beam (FIB) unit for serial sectioning with high-resolution field emission scanning electron microscopy equipped with EBSD. The work demonstrates that the new 3D EBSD-FIB technique provides a new level of microstructure information that cannot be achieved by conventional 2D-EBSD analysis.

Abstract: The variations of in plane Charpy toughness anisotropy as a function of the microstructure and texture of an industrial grade of API –X80 pipeline steel was studied. Standard size Charpy samples with a long axis orientated at 0, 22.5, 45, 67.5 and 90° with respect to the rolling direction of the plate were tested at different temperatures varying from -196°C to 20°C. Microstructure and texture of the plates were investigated by means of electron backscattering diffraction (EBSD), XRD and the recently developed 3D EBSD technique. The spatial grain shape orientation distribution was examined on samples which were cut from the middle thickness of an industrial rolled plate by means of 3D EBSD and following grain shape reconstruction and approximation of the grain shape with ellipsoids. It was found that the experimentally observed 3D microstructures could well be correlated to the anisotropy of the measured Charpy impact toughness of the steel for the Charpy samples. The Charpy toughness anisotropy of the plates in the transition region where both ductile and brittle fractures take place can be related to the microstructural anisotropy characterized by the grain shape orientation and the spatial distribution of the 2nd phase.

Abstract: An extra low carbon steel was cold rolled to 85% reduction and annealed at 680 °C to generate a microstructure containing ~2 % recrystallized grains. A partly recrystallized volume was analyzed using 3-D FIB-EBSD tomography. The results show that nucleation and subsequent growth of recrystallizing grains is more complex processes than that revealed using 2-D metallographic techniques. In the present steel, it was found that subgrains were found to be the origin of nucleation and these grains exhibit an internal structure similar to the surrounding deformation substructure. However, a certain subgrain keeps expanding to a stage where some part or parts of the boundary reach(es) and consume(s) a high stored energy deformation zone(s) to form (a) local dislocation free zone(s) having an orientation similar to the subgrain. After this stage, the residual dislocations in the original subgrain are annihilated and nuclei enter a well-defined growth stage. The overall growth of recrystallization nuclei was found to be controlled by the variation in both the stored energy and orientation of the surrounding deformation substructure that results in heterogeneous growth by so-called orientation pinning.

Abstract: The microstructural anisotropy together with the crystallographic texture of an industrial grade of X70 pipeline steel is studied by means of the 3D-EBSD technique known also as EBS3 which was recently developed by FEI. Samples of size 8x10x3mm³ were cut from the middle thickness of an industrial rolled plate and after special sample preparation have been studied in a Nova 600 dual beam scanning electron microscope equipped with a field emission gun and HKL Channel 6 EBSD data collection software for crystallographic orientation, which allows multiple sectioning of the sample in automatic mode and, afterwards reconstruction of both the 3D microstructure and texture of the examined volume. Three scanned zones of different volumes that varied between 15x10x27 4m³ and 16x14x6 4m³ have been examined and the results for the crystallographic orientation, grain shape and grain shape orientation are discussed together with the data for the anisotropy of the Charpy impact toughness of the material.

Abstract: This work studies the rotations of a (111) Cu single crystal due to the application of a conical nanoindent. With the aid of a joint high-resolution field emission SEM-EBSD set-up coupled with serial sectioning in a focused ion beam (FIB) system in the form of a cross-beam 3D crystal orientation microscope (3D EBSD) a 3D rotation map underneath the indent could be extracted. When analyzing the rotation directions in the cross section planes (11-2) perpendicular to the (111) surface plane below the indenter tip we observe multiple transition regimes with steep orientation gradients and changes in rotation direction. A phenomenological and a physically-based 3D elastic-viscoplastic crystal plasticity model are implemented in two finite element simulations adopting the geometry and boundary conditions of the experiment. While the phenomenological model predicts the general rotation trend it fails to describe the fine details of the rotation patterning with the frequent changes in sign observed in the experiment. The physically-based model, which is a dislocation density based constitutive model, succeeded to precisely predict the crystal rotation map compared with the experiment. Both simulations over-emphasize the magnitude of the rotation field near the indenter relative to that measured directly below the indenter tip. However, out of the two models the physically-based model reveals better crystal rotation angles

Abstract: Orientation microscopy in TEM and SEM is a particularly well suited tool to study recrystallisation processes because these are always associated with orientation and microstructure changes. The present work discusses the possibilities and limits of the TEM and SEM based techniques and illustrates their use by means of 3 different examples. The examples include studies on nucleation mechanisms of primary recrystallisation where the techniques meet their limits in spatial resolution. The problem of in-situ observations of annealing processes is discussed and it is shown how recrystallisation simulation techniques based on experimental data may be used. Furthermore the new technique of 3-dimensional EBSD in a focused-ion-beam (FIB) SEM is presented with one example. Finally, the statistical analysis of very large orientation data sets is discussed by an example of secondary recrystallisation in electrical steels.