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Abstract We present two new methods of processing data from backscattered electron signals in a scanning electron microscope to image grains and subgrains. The first combines data from multiple backscattered electron images acquired at different specimen geometries to (1) better reveal grain boundaries in recrystallized microstructures and (2) distinguish between recrystallized and unrecrystallized regions in partially recrystallized microstructures. The second utilizes spherical harmonic transform indexing of electron backscatter diffraction patterns to produce high angular resolution orientation data that enable the characterization of subgrains. Subgrains are produced during high-temperature plastic deformation and have boundary misorientation angles ranging from a few degrees down to a few hundredths of a degree. We also present an algorithm to automatically segment grains from combined backscattered electron image data or grains and subgrains from high angular resolution electron backscatter diffraction data. Together, these new techniques enable rapid measurements of individual grains and subgrains from large populations.
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Electron Backscatter Diffraction Patterns from Titanium-added Interstitial-free Steel Containing Subgrains
Associated Publications Bennett IV, T.J. and Taleff, E.M. Dynamic Grain Growth Driven by Subgrain Boundaries in an Interstitial-Free Steel During Deformation at 850 °C. Metall Mater Trans A 55, 429–446 (2024). https://doi.org/10.1007/s11661-023-07256-w. Bennett IV, T.J. and Taleff, E.M. Imaging and Segmenting Grains and Subgrains using Backscattered Electron Techniques. Under review (2024). Data Description These data were collected by Thomas J. Bennett IV on July 28, 2022. The electron backscatter diffraction (EBSD) data and associated electron backscatter diffraction patterns (EBSPs) contained herein were acquired from a titanium-added interstitial-free (Ti-IF) steel sheet material containing numerous subgrains. The Ti-IF steel specimen that provided these data was ramped to 850 degrees Celsius over 30 minutes, held at this temperature for one hour, and then deformed at a constant true-strain rate of 10^-4 s^-1. Upon reaching a final true strain of 0.225, the specimen was air quenched while maintaining a constant stress to preserve subgrains formed during high-temperature deformation. The tensile specimen was cut from a Ti-IF steel sheet received in a hard as-rolled condition with the tensile axis parallel to the sheet rolling direction. EBSPs were acquired from a section cut from the center of the deformed gage region using a JEOL JSM-IT300HR SEM equipped with an EDAX Velodity EBSD camera at the Center for Integrated Nanotechnologies. The following conditions were used for EBSD data acquisition: Accelerating Voltage: 20 kV Beam Current: 80% Working Distance: 20.0 mm Magnification: 200× Dynamic Focus: 44 (out of 255, arbitrary units) Specimen Tilt: 70 degrees Scanning Grid Type: Square Step Size (x and y): 0.5 μm Scan Size: 520 (across) × 340 (down) pixels EBSD Camera Resolution: 446 × 446 pixels EBSD Camera Binning: 1 × 1 EBSD Camera Exposure Time: 10 ms Frame Averaging: None Specimen Tensile Direction: Horizontal Specimen Rolling Direction: Horizontal Specimen Long Transverse Direction: Vertical Specimen Short Transverse Direction: Normal to plane Pattern Center (EMSphInx Convention): (x_pc, y_pc, L) = (-0.2 pixels, 112.76 pixels, 21736.4 μm) EBSD Camera Elevation Angle: 3 degrees EBSD Camera Screen Width: 32 mm Pixel size on EBSD Camera Screen: 71.749 μm/pixel ( = 32000 μm / 446 pixels) Note: Conversions between different pattern center conventions may be found in the journal article below or at the following link: https://github.com/EMsoft-org/EMsoft/wiki/DItutorial. Jackson, M.A., Pascal, E., and De Graef, M. Dictionary Indexing of Electron Back-Scatter Diffraction Patterns: a Hands-On Tutorial. Integr Mater Manuf Innov 8, 226–246 (2019). https://doi.org/10.1007/s40192-019-00137-4. File Descriptions Specimen_orientation.pdf - A schematic showing specimen reference directions and the orientation used for EBSD data acquisition. Patterns.zip - A compressed archive containing Patterns.up2. This file contains 16-bit EBSPs and is 70,336,697,616 bytes (70.3 GB) uncompressed. SHT_Indexed.ang - A file containing orientation data produced by indexing Patterns.up2 using EMSphInx. Orientations are represented by Euler angles (Bunge convention) and are to be interpreted using the EDAX Setting 2 convention (see MTEX documentation at https://mtex-toolbox.github.io/EBSDReferenceFrame.html). SHT_Indexed.h5 - A file in HDF5 format containing orientation data and other relevant information produced by indexing Patterns.up2 using EMSphInx. SHT_Indexed_IPFmap.png - An image of an inverse pole figure map colored with respect to the short transverse direction showing the data from SHT_Indexed.ang. Note: The basic format of "up2" files is the following. The first 4 bytes provide the version number. The second 4 bytes are the width of the patterns. The third 4 bytes are the height of the patterns. The fourth 4 bytes are the starting position of the pattern image data. Acknowledgments The authors gratefully acknowledge support from the National Science Foundation under Grant DMR-2003312 and instrumentation under Grant DMR-9974476. The authors also gratefully acknowledge support from the U.S. Department of Energy, Office of High Energy Physics under Grant DE-SC0009960. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Los Alamos National Laboratory (Contract 89233218CNA000001) and Sandia National Laboratories (Contract DE-NA-0003525). The authors thank Mr. Thomas Cayia (Arcelor Mittal) for providing the interstitial-free steel material used for this study.
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- Award ID(s):
- 2003312
- PAR ID:
- 10570310
- Publisher / Repository:
- Zenodo
- Date Published:
- Format(s):
- Medium: X
- Location:
- https://zenodo.org/records/11403783
- Right(s):
- Creative Commons Attribution 4.0 International
- Institution:
- The University of Texas at Austin
- Sponsoring Org:
- National Science Foundation
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