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Title: Effect of strain rate and dislocation density on the twinning behavior in Tantalum

The conditions which affect twinning in tantalum have been investigated across a range of strain rates and initial dislocation densities. Tantalum samples were subjected to a range of strain rates, from 10–4/s to 103/s under uniaxial stress conditions, and under laser-induced shock-loading conditions. In this study, twinning was observed at 77K at strain rates from 1/s to 103/s, and during laser-induced shock experiments. The effect of the initial dislocation density, which was imparted by deforming the material to different amounts of pre-strain, was also studied, and it was shown that twinning is suppressed after a given amount of pre-strain, even as the global stress continues to increase. These results indicate that the conditions for twinning cannot be represented solely by a critical global stress value, but are also dependent on the evolution of the dislocation density. Additionally, the analysis shows that if twinning is initiated, the nucleated twins may continue to grow as a function of strain, even as the dislocation density continues to increase.
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [1] ;  [1] ;  [4] ;  [4] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. TerraPower LLC, Bellevue, WA (United States)
  3. Univ. of Illinois at Urbana Champaign, Urbana, IL (United States)
  4. John Hopkins Univ., Baltimore, MD (United States)
Publication Date:
OSTI Identifier:
1249830
Report Number(s):
LLNL-JRNL-687200
Journal ID: ISSN 2158-3226; AAIDBI
Grant/Contract Number:
AC52-07NA27344; AC52-06NA25396
Type:
Published Article
Journal Name:
AIP Advances
Additional Journal Information:
Journal Volume: 6; Journal Issue: 4; Journal ID: ISSN 2158-3226
Publisher:
American Institute of Physics (AIP)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; stress strain relations; Tantalum; testing procedures; polycrystals; transmission electron microscopy