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Title: Transition of dislocation glide to shear transformation in shocked tantalum

Abstract

A TEM study of pure tantalum and tantalum-tungsten alloys explosively shocked at a peak pressure of 30 GPa (strain rate: ~1 x 10 4 sec -1) is presented. While no ω (hexagonal) phase was found in shock-recovered pure Ta and Ta-5W that contain mainly a low-energy cellular dislocation structure, shock-induced ω phase was found to form in Ta-10W that contains evenly distributed dislocations with a stored dislocation density higher than 1 x 10 12 cm -2. The TEM results clearly reveal that shock-induced α (bcc) → ω (hexagonal) shear transformation occurs when dynamic recovery reactions which lead the formation low-energy cellular dislocation structure become largely suppressed in Ta-10W shocked under dynamic (i.e., high strain-rate and high-pressure) conditions. A novel dislocation-based mechanism is proposed to rationalize the transition of dislocation glide to twinning and/or shear transformation in shock-deformed tantalum. Lastly, twinning and/or shear transformation take place as an alternative deformation mechanism to accommodate high-strain-rate straining when the shear stress required for dislocation multiplication exceeds the threshold shear stresses for twinning and/or shear transformation.

Authors:
 [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1347662
Report Number(s):
LLNL-JRNL-710038
Journal ID: ISSN 2059-8521; applab
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
MRS Advances
Additional Journal Information:
Journal Volume: 2; Journal Issue: 27; Journal ID: ISSN 2059-8521
Publisher:
Materials Research Society (MRS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Hsiung, Luke L., and Campbell, Geoffrey H. Transition of dislocation glide to shear transformation in shocked tantalum. United States: N. p., 2017. Web. doi:10.1557/adv.2017.236.
Hsiung, Luke L., & Campbell, Geoffrey H. Transition of dislocation glide to shear transformation in shocked tantalum. United States. doi:10.1557/adv.2017.236.
Hsiung, Luke L., and Campbell, Geoffrey H. Tue . "Transition of dislocation glide to shear transformation in shocked tantalum". United States. doi:10.1557/adv.2017.236. https://www.osti.gov/servlets/purl/1347662.
@article{osti_1347662,
title = {Transition of dislocation glide to shear transformation in shocked tantalum},
author = {Hsiung, Luke L. and Campbell, Geoffrey H.},
abstractNote = {A TEM study of pure tantalum and tantalum-tungsten alloys explosively shocked at a peak pressure of 30 GPa (strain rate: ~1 x 104 sec-1) is presented. While no ω (hexagonal) phase was found in shock-recovered pure Ta and Ta-5W that contain mainly a low-energy cellular dislocation structure, shock-induced ω phase was found to form in Ta-10W that contains evenly distributed dislocations with a stored dislocation density higher than 1 x 1012 cm-2. The TEM results clearly reveal that shock-induced α (bcc) → ω (hexagonal) shear transformation occurs when dynamic recovery reactions which lead the formation low-energy cellular dislocation structure become largely suppressed in Ta-10W shocked under dynamic (i.e., high strain-rate and high-pressure) conditions. A novel dislocation-based mechanism is proposed to rationalize the transition of dislocation glide to twinning and/or shear transformation in shock-deformed tantalum. Lastly, twinning and/or shear transformation take place as an alternative deformation mechanism to accommodate high-strain-rate straining when the shear stress required for dislocation multiplication exceeds the threshold shear stresses for twinning and/or shear transformation.},
doi = {10.1557/adv.2017.236},
journal = {MRS Advances},
issn = {2059-8521},
number = 27,
volume = 2,
place = {United States},
year = {2017},
month = {2}
}

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Works referenced in this record:

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