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

Shuang Cui, Zezhou Li, Shiteng Zhao, Bingfeng Wang, Renkun Chen, Ruslan Valiev, Marc Meyers

Research output: Contribution to journalArticlepeer-review

32 Scopus Citations

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 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.
Original languageAmerican English
Pages (from-to)408-422
Number of pages15
JournalActa Materialia
Volume181
DOIs
StatePublished - 2019

NREL Publication Number

  • NREL/JA-5500-75304

Keywords

  • adiabatic shear localization at cryogenic temperatures
  • coarse-grained titanium
  • dynamic response
  • nanograins
  • ultrafine-grained titanium

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