Papers by Author: Stuart I. Wright

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Authors: Stuart I. Wright, John Bingert, Thomas A. Mason, Ryan J. Larsen
Authors: Stuart I. Wright, Jay A. Basinger, Matthew M. Nowell
Abstract: Electron backscatter diffraction (EBSD) has become the preferred technique for characterizing the crystallographic orientation of individual grains in polycrystalline microstructures due to its ability to rapidly measure orientations at specific points in the microstructure at resolutions of approximately 20-50nm depending on the capabilities of the scanning electron microscope (SEM) and on the material being characterized. Various authors have studied the angular resolution of the orientations measured using automated EBSD. These studies have stated values ranging from approximately 0.1° to 2° [1-6]. Various factors influence the angular resolution achievable. The two primary factors are the accuracy of the detection of the bands in the EBSD patterns and the accuracy of the pattern center (PC) calibration. The band detection is commonly done using the Hough transform. The effect of varying the Hough transform parameters in order to optimize speed has been explored in a previous work [6]. The present work builds upon the earlier work but with the focus towards achieving the best angular resolution possible regardless of speed. This work first details the methodology used to characterize the angular precision then reports on various approaches to optimizing parameters to improve precision.
Authors: Richard Penelle, Thierry Baudin, David J. Dingley, M. Tiner, Stuart I. Wright
Authors: Stuart I. Wright, Matthew M. Nowell
Abstract: Automated Electron Backscatter Diffraction (EBSD) or Orientation Imaging Microscopy (OIM) has proven to be a viable technique for investigating microtexture in polycrystalline materials. It is particularly useful for investigating orientation relationships between phases in multiphase materials. However, when phases do not significantly vary in crystallographic structure, OIM is limited in its capability to reliably differentiate between phases. Through simultaneous collection of EBSD data and chemical data via X-Ray Energy Dispersive Spectroscopy (EDS) it is possible to dramatically improve upon the phase differentiation capabilities of either technique individually. This presentation will introduce a methodology for combining the two techniques as well as show a few example applications.
Authors: Christopher A. Michaluk, David P. Field, Kevin A. Nibur, Stuart I. Wright, Ronald A. Witt
Authors: Stuart I. Wright, David P. Field, Matthew M. Nowell
Abstract: While electron backscatter diffraction (EBSD) has become an established technique within materials characterization labs around the world, the technique is still relatively young and new applications are continuing to emerge. Automated EBSD or Orientation Imaging Microscopy (OIM) systems are being used in combination with other equipment within the scanning electron microscope (SEM) to perform in-situ measurements. This includes tensile stages for observing changes in local orientation during deformation and heating stages for studying orientation changes arising during recrystallization and grain growth as well as phase transformations. In addition to these temporally three-dimensional studies, spatially three-dimensional studies can be performed by in-situ serial sectioning in microscopes equipped with both electron and focused ion beams. These in-situ techniques are briefly reviewed. The review is followed by a detailed analysis of in-situ heating experiments on copper. The movement of grain boundaries during recrystallization and subsequent grain growth are tracked. The effect of orientation relationships on grain boundary mobility and nucleation are explored. No special relationship with grain boundary mobility was observed. However, twins appear to play a significant role in the nucleation process.
Authors: Matthew M. Nowell, David P. Field, Stuart I. Wright, T.M. Lillo
Authors: David P. Field, Matthew M. Nowell, P. Trivedi, Stuart I. Wright, T.M. Lillo
Abstract: The texture and grain boundary structure of recrystallized materials is dependent upon the character of the deformed matrix, and the selective nucleation and growth of crystallites from the deformation structure. Proper description of the deformed matrix includes not only local crystallite lattice orientation, but also dislocation content and gradients in structural features that contribute to the heterogeneity of the nucleation and growth processes. In-situ recrystallization experiments were performed on pure copper deformed by equal channel angular extrusion, and characterization of the structure on the surface of bulk specimens was accomplished using the EBSD technique. The character of the structure where nucleation preferentially occurs is presumed to be in heavily deformed regions as nuclei were first observed in such microstructures. Grain growth is observed to be heavily dependent upon twinning processes.
Authors: David P. Field, Stuart I. Wright, P. Trivedi
Authors: Stuart I. Wright, F. Heidelbach
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