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Title: An investigation of geometrically necessary dislocations and back stress in large grained tantalum via EBSD and CPFEM

Abstract

This study explores the evolution of GNDs and their effects on back stress through experimental and computational methods. Four large-grained tantalum tensile specimens were strained in uniaxial tension, electron backscatter diffraction (EBSD) data were collected, and geometrically necessary dislocation (GND) maps of the four specimens in the unloaded state were produced. EBSD-based GND maps revealed several types of features with high GND content which caused back stress in the specimens. Correlations between five geometrically-based grain boundary (GB) transmission factors and the GB GND content were evaluated, and statistically significant correlations were found for transmission factors based on Livingston and Chalmer’s N factor, Werner and Prantl’s slip transfer number, and GB misorientation. The sign of individual components of the Nye tensor were used to visually and quantitatively identify clustering of GNDs of the same sign, thus giving additional evidence of increasing back stress due to deformation. Deformation of one of the specimens was simulated using multiple CPFEM based modeling approaches and predicted stress-strain responses are compared. The super dislocation model (SD model) — a crystal plasticity finite element method (CPFEM) which incorporates elastic dislocation interactions — was able to isolate impact of back stress on the overall flow stress. The SDmore » model predicted correct stresses when compared with experimental data; however, when the elastic interactions in the SD model were turned off, stress predictions were 25% too low. Thus, demonstrating the importance of incorporating back stress into the model.« less

Authors:
 [1];  [1];  [1];  [2];  [3];  [3];  [2];  [2]
  1. Brigham Young Univ., Provo, UT (United States)
  2. The Ohio State Univ., Columbus, OH (United States)
  3. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Brigham Young Univ., Provo, UT (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1603227
Alternate Identifier(s):
OSTI ID: 1581661
Grant/Contract Number:  
SC0012587; SC0012483
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing
Additional Journal Information:
Journal Volume: 772; Journal Issue: C; Journal ID: ISSN 0921-5093
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; back stress; ebsd; gnd; tantalum; cpfem

Citation Formats

Hansen, Landon T., Fullwood, David T., Homer, Eric R., Wagoner, Robert H., Lim, Hojun, Carroll, Jay D., Zhou, Guowei, and Bong, Hyuk Jong. An investigation of geometrically necessary dislocations and back stress in large grained tantalum via EBSD and CPFEM. United States: N. p., 2019. Web. doi:10.1016/j.msea.2019.138704.
Hansen, Landon T., Fullwood, David T., Homer, Eric R., Wagoner, Robert H., Lim, Hojun, Carroll, Jay D., Zhou, Guowei, & Bong, Hyuk Jong. An investigation of geometrically necessary dislocations and back stress in large grained tantalum via EBSD and CPFEM. United States. https://doi.org/10.1016/j.msea.2019.138704
Hansen, Landon T., Fullwood, David T., Homer, Eric R., Wagoner, Robert H., Lim, Hojun, Carroll, Jay D., Zhou, Guowei, and Bong, Hyuk Jong. 2019. "An investigation of geometrically necessary dislocations and back stress in large grained tantalum via EBSD and CPFEM". United States. https://doi.org/10.1016/j.msea.2019.138704. https://www.osti.gov/servlets/purl/1603227.
@article{osti_1603227,
title = {An investigation of geometrically necessary dislocations and back stress in large grained tantalum via EBSD and CPFEM},
author = {Hansen, Landon T. and Fullwood, David T. and Homer, Eric R. and Wagoner, Robert H. and Lim, Hojun and Carroll, Jay D. and Zhou, Guowei and Bong, Hyuk Jong},
abstractNote = {This study explores the evolution of GNDs and their effects on back stress through experimental and computational methods. Four large-grained tantalum tensile specimens were strained in uniaxial tension, electron backscatter diffraction (EBSD) data were collected, and geometrically necessary dislocation (GND) maps of the four specimens in the unloaded state were produced. EBSD-based GND maps revealed several types of features with high GND content which caused back stress in the specimens. Correlations between five geometrically-based grain boundary (GB) transmission factors and the GB GND content were evaluated, and statistically significant correlations were found for transmission factors based on Livingston and Chalmer’s N factor, Werner and Prantl’s slip transfer number, and GB misorientation. The sign of individual components of the Nye tensor were used to visually and quantitatively identify clustering of GNDs of the same sign, thus giving additional evidence of increasing back stress due to deformation. Deformation of one of the specimens was simulated using multiple CPFEM based modeling approaches and predicted stress-strain responses are compared. The super dislocation model (SD model) — a crystal plasticity finite element method (CPFEM) which incorporates elastic dislocation interactions — was able to isolate impact of back stress on the overall flow stress. The SD model predicted correct stresses when compared with experimental data; however, when the elastic interactions in the SD model were turned off, stress predictions were 25% too low. Thus, demonstrating the importance of incorporating back stress into the model.},
doi = {10.1016/j.msea.2019.138704},
url = {https://www.osti.gov/biblio/1603227}, journal = {Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing},
issn = {0921-5093},
number = C,
volume = 772,
place = {United States},
year = {2019},
month = {11}
}

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