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Title: Helium bubble formation in ultrafine and nanocrystalline tungsten under different extreme conditions

We investigated the effects of helium ion irradiation energy and sample temperature on the performance of grain boundaries as helium sinks in ultrafine grained and nanocrystalline tungsten. Irradiations were performed at displacement and non-displacement energies and at temperatures above and below that required for vacancy migration. Microstructural investigations were performed using Transmission Electron Microscopy (TEM) combined with either in-situ or ex-situ ion irradiation. Under helium irradiation at an energy which does not cause atomic displacements in tungsten (70 eV), regardless of temperature and thus vacancy migration conditions, bubbles were uniformly distributed with no preferential bubble formation on grain boundaries. Moreover, at energies that can cause displacements, bubbles were observed to be preferentially formed on the grain boundaries only at high temperatures where vacancy migration occurs. Under these conditions, the decoration of grain boundaries with large facetted bubbles occurred on nanocrystalline grains with dimensions less than 60 nm. Finally, we discuss the importance of vacancy supply and the formation and migration of radiation-induced defects on the performance of grain boundaries as helium sinks and the resulting irradiation tolerance of ultrafine grained and nanocrystalline tungsten to bubble formation.
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [4] ;  [5]
  1. Purdue Univ., Birck Nanotechnology Center, and Center for Material Under Extreme Environment, West Lafayette, IN (United States)
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  3. Univ. of Huddersfield (United Kingdom)
  4. Purdue Univ., West Lafayette, IN (United States); Center for Materials Uncer Extreme Environment, West Lafayette, IN (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  5. Purdue Univ., West Lafayette, IN (United States); Center for Materials Uncer Extreme Environment, West Lafayette, IN (United States)
Publication Date:
OSTI Identifier:
1183004
Report Number(s):
SAND2014--15238J
Journal ID: ISSN 0022-3115; 534153
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 458; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Research Org:
Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY