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Title: Investigation of the shear response and geometrically necessary dislocation densities in shear localization in high-purity titanium

The influence of microstructural anisotropy on shear response of high-purity titanium was studied using the compact forced-simple-shear specimen (CFSS) loaded under quasi-static loading conditions. Post-mortem characterization reveals significant difference in shear response of different directions in the same material due to material crystallographic texture anisotropy. Shear bands are narrower in specimens in which the shear zone is aligned along the direction with a strong {0001} basal texture. Twinning was identified as an active mechanism to accommodate strains in the shear region in both orientations. This paper confirms the applicability of the CFSS design for the investigation of differences in the shear response of materials as a function of process-induced crystallographic texture. A detailed, systematic approach to quantifying shear band evolution by evaluating geometrically necessary dislocations (GND) associated with crystallographic anisotropy is presented. Finally, the results show that: i) line average GND density profiles, for Ti samples that possess a uniform equiaxed-grain structure, but with strong crystallographic anisotropy, exhibit significant differences in GND density close to the shear band center; ii) GND profiles decrease steadily away from the shear band as the plastic strain diminishes, in agreement with Ashby's theory of work hardening, where the higher GND density in the through-thicknessmore » (TT) orientation is a result of restricted < a > type slip in the shear band compared with in-plane (IP) samples; iii) the anisotropy in deformation response is derived from initial crystallographic texture of the materials, where GND density of < a > GNDs are higher adjacent to the shear band in the through-thickness sample oriented away from easy slip, but the density of < c+a > type GNDs are very similar in these two samples; and iv) the increase in grain average GND density was determined to have strong correlation to an increase in the Euler Φ angle of the grain average orientation, indicating an increased misorientation angle evolution.« less
Authors:
ORCiD logo [1] ;  [2] ;  [1] ;  [2] ;  [2] ; ORCiD logo [1]
  1. Univ. of California, San Diego, CA (United States). Dept. of NanoEngineering
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-16-22158
Journal ID: ISSN 0749-6419
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
International Journal of Plasticity
Additional Journal Information:
Journal Volume: 92; Journal ID: ISSN 0749-6419
Publisher:
Elsevier
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); USDOD
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Shear banding; Geometrically necessary dislocations; CFSS sample; Crystallographic anisotropy
OSTI Identifier:
1360700
Alternate Identifier(s):
OSTI ID: 1416626

Zhu, Chaoyi, Livescu, Veronica, Harrington, Tyler, Dippo, Olivia, Gray, George T., and Vecchio, Kenneth S.. Investigation of the shear response and geometrically necessary dislocation densities in shear localization in high-purity titanium. United States: N. p., Web. doi:10.1016/j.ijplas.2017.03.009.
Zhu, Chaoyi, Livescu, Veronica, Harrington, Tyler, Dippo, Olivia, Gray, George T., & Vecchio, Kenneth S.. Investigation of the shear response and geometrically necessary dislocation densities in shear localization in high-purity titanium. United States. doi:10.1016/j.ijplas.2017.03.009.
Zhu, Chaoyi, Livescu, Veronica, Harrington, Tyler, Dippo, Olivia, Gray, George T., and Vecchio, Kenneth S.. 2017. "Investigation of the shear response and geometrically necessary dislocation densities in shear localization in high-purity titanium". United States. doi:10.1016/j.ijplas.2017.03.009. https://www.osti.gov/servlets/purl/1360700.
@article{osti_1360700,
title = {Investigation of the shear response and geometrically necessary dislocation densities in shear localization in high-purity titanium},
author = {Zhu, Chaoyi and Livescu, Veronica and Harrington, Tyler and Dippo, Olivia and Gray, George T. and Vecchio, Kenneth S.},
abstractNote = {The influence of microstructural anisotropy on shear response of high-purity titanium was studied using the compact forced-simple-shear specimen (CFSS) loaded under quasi-static loading conditions. Post-mortem characterization reveals significant difference in shear response of different directions in the same material due to material crystallographic texture anisotropy. Shear bands are narrower in specimens in which the shear zone is aligned along the direction with a strong {0001} basal texture. Twinning was identified as an active mechanism to accommodate strains in the shear region in both orientations. This paper confirms the applicability of the CFSS design for the investigation of differences in the shear response of materials as a function of process-induced crystallographic texture. A detailed, systematic approach to quantifying shear band evolution by evaluating geometrically necessary dislocations (GND) associated with crystallographic anisotropy is presented. Finally, the results show that: i) line average GND density profiles, for Ti samples that possess a uniform equiaxed-grain structure, but with strong crystallographic anisotropy, exhibit significant differences in GND density close to the shear band center; ii) GND profiles decrease steadily away from the shear band as the plastic strain diminishes, in agreement with Ashby's theory of work hardening, where the higher GND density in the through-thickness (TT) orientation is a result of restricted < a > type slip in the shear band compared with in-plane (IP) samples; iii) the anisotropy in deformation response is derived from initial crystallographic texture of the materials, where GND density of < a > GNDs are higher adjacent to the shear band in the through-thickness sample oriented away from easy slip, but the density of < c+a > type GNDs are very similar in these two samples; and iv) the increase in grain average GND density was determined to have strong correlation to an increase in the Euler Φ angle of the grain average orientation, indicating an increased misorientation angle evolution.},
doi = {10.1016/j.ijplas.2017.03.009},
journal = {International Journal of Plasticity},
number = ,
volume = 92,
place = {United States},
year = {2017},
month = {3}
}