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Title: The Effects of Ultra-Fine-Grained Structure and Cryogenic Temperature on Adiabatic Shear Localization in Titanium

Abstract

The deformation at low temperatures (173 K and 77 K) in ultrafine-grained (100 and 500 nm) titanium is investigated and its effect on adiabatic shear localization is established. In comparison with coarse-grained titanium, the strength of ultrafine-grained titanium is higher due to the classic Hall-Petch effect while the strain hardening approaches zero. Our results show that shear localization in dynamic deformation is also altered. The width of the shear band of coarse-grained titanium decreases from 30 to 18 um (by 40%) with decreasing the initial deformation temperature to 77 K. In contrast, for 100 nm titanium, the width of shear band decreases more significantly, from 4 um at room temperature to 1 um (a 75% decrease) at 77 K. This difference is attributed to the combined effects of the decrease in the thermal conductivity and specific heat capacity, and the increase in thermal softening rate. These changes in the width are consistent with the predictions of the Grady and Bai-Dodd theories. Ultrafine- and nano- recrystallized grains are observed inside the bands which are dependent on initial grain size and initial deformation temperature. The dislocation evolution is evaluated for the different conditions using a Kocks-Mecking formulation; the rotational dynamic recrystallization mechanismmore » responsible for forming the ultrafine/nanosized grains (40-250 nm) is successfully modeled incorporating the differences in initial temperature and grain size. Our results and analysis are important in enhancing the understanding of the structural evolution processes under high strain-rates and cryogenic temperatures.« less

Authors:
 [1];  [2];  [3]; ORCiD logo [4];  [1];  [5];  [1]
  1. University of California, San Diego
  2. University of California, Berkeley
  3. Central South University
  4. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
  5. Ufa State Aviation Technical University
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Security (NA-70)
OSTI Identifier:
1573200
Report Number(s):
NREL/JA-5500-75304
DOE Contract Number:  
AC36-08GO28308
Resource Type:
Journal Article
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 181
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; coarse-grained titanium; ultrafine-grained titanium; dynamic response; adiabatic shear localization at cryogenic temperatures; nanograins

Citation Formats

Li, Zezhou, Zhao, Shiteng, Wang, Bingfeng, Cui, Shuang, Chen, Renkun, Valiev, Ruslan Z., and Meyers, Marc A. The Effects of Ultra-Fine-Grained Structure and Cryogenic Temperature on Adiabatic Shear Localization in Titanium. United States: N. p., 2019. Web. doi:10.1016/j.actamat.2019.09.011.
Li, Zezhou, Zhao, Shiteng, Wang, Bingfeng, Cui, Shuang, Chen, Renkun, Valiev, Ruslan Z., & Meyers, Marc A. The Effects of Ultra-Fine-Grained Structure and Cryogenic Temperature on Adiabatic Shear Localization in Titanium. United States. doi:10.1016/j.actamat.2019.09.011.
Li, Zezhou, Zhao, Shiteng, Wang, Bingfeng, Cui, Shuang, Chen, Renkun, Valiev, Ruslan Z., and Meyers, Marc A. Wed . "The Effects of Ultra-Fine-Grained Structure and Cryogenic Temperature on Adiabatic Shear Localization in Titanium". United States. doi:10.1016/j.actamat.2019.09.011.
@article{osti_1573200,
title = {The Effects of Ultra-Fine-Grained Structure and Cryogenic Temperature on Adiabatic Shear Localization in Titanium},
author = {Li, Zezhou and Zhao, Shiteng and Wang, Bingfeng and Cui, Shuang and Chen, Renkun and Valiev, Ruslan Z. and Meyers, Marc A.},
abstractNote = {The deformation at low temperatures (173 K and 77 K) in ultrafine-grained (100 and 500 nm) titanium is investigated and its effect on adiabatic shear localization is established. In comparison with coarse-grained titanium, the strength of ultrafine-grained titanium is higher due to the classic Hall-Petch effect while the strain hardening approaches zero. Our results show that shear localization in dynamic deformation is also altered. The width of the shear band of coarse-grained titanium decreases from 30 to 18 um (by 40%) with decreasing the initial deformation temperature to 77 K. In contrast, for 100 nm titanium, the width of shear band decreases more significantly, from 4 um at room temperature to 1 um (a 75% decrease) at 77 K. This difference is attributed to the combined effects of the decrease in the thermal conductivity and specific heat capacity, and the increase in thermal softening rate. These changes in the width are consistent with the predictions of the Grady and Bai-Dodd theories. Ultrafine- and nano- recrystallized grains are observed inside the bands which are dependent on initial grain size and initial deformation temperature. The dislocation evolution is evaluated for the different conditions using a Kocks-Mecking formulation; the rotational dynamic recrystallization mechanism responsible for forming the ultrafine/nanosized grains (40-250 nm) is successfully modeled incorporating the differences in initial temperature and grain size. Our results and analysis are important in enhancing the understanding of the structural evolution processes under high strain-rates and cryogenic temperatures.},
doi = {10.1016/j.actamat.2019.09.011},
journal = {Acta Materialia},
number = ,
volume = 181,
place = {United States},
year = {2019},
month = {9}
}