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Title: Modeling of grain size strengthening in tantalum at high pressures and strain rates

Laser-driven ramp wave compression experiments have been used to investigate the strength (flow stress) of tantalum and other metals at high pressures and high strain rates. Recently this kind of experiment has been used to assess the dependence of the strength on the average grain size of the material, finding no detectable variation with grain size. The insensitivity to grain size has been understood theoretically to result from the dominant effect of the high dislocation density generated at the extremely high strain rates of the experiment. Here we review the experiments and describe in detail the multiscale strength model used to simulate them. The multiscale strength model has been extended to include the effect of geometrically necessary dislocations generated at the grain boundaries during compatible plastic flow in the polycrystalline metal. Lastly, we use the extended model to make predictions of the threshold strain rates and grain sizes below which grain size strengthening would be observed in the laser-driven Rayleigh-Taylor experiments.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-675719
Journal ID: ISSN 0094-243X; TRN: US1701053
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
AIP Conference Proceedings
Additional Journal Information:
Journal Volume: 1793; Journal ID: ISSN 0094-243X
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
OSTI Identifier:
1345315