Effects of grain size and deformation temperature on hydrogen-enhanced vacancy formation in Ni alloys

Samantha K. Lawrence*, Yuriy Yagodzinskyy, Hannu Hänninen, Esa Korhonen, Filip Tuomisto, Zachary D. Harris, Brian P. Somerday

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

46 Citations (Scopus)

Abstract

Positron annihilation spectroscopy and thermal desorption spectroscopy experiments were combined to ascertain the role of hydrogen on generation of vacancies and vacancy clusters in Ni alloys. The effects of grain size and deformation temperature are emphasized for pure Ni single crystals and polycrystalline Ni-201 alloy samples with two grain sizes that were thermally pre-charged with 3000 appm hydrogen. Variation in positron lifetime and intensity suggests that hydrogen enhances and stabilizes vacancies and vacancy clusters. Additionally, grain boundaries and the regions adjacent to them are preferential sites for vacancy and cluster formation. Hydrogen-altered vacancies and vacancy clusters are manifest in yield behavior differences: uniform vacancy distributions augment strength increases after hydrogen charging; enhanced yield strength during cryogenic deformation is ascribed to an ‘Orowan type’ strengthening mechanism while cross-slip restriction dominates hardening behavior at room temperature.

Original languageEnglish
Pages (from-to)218-226
Number of pages9
JournalActa Materialia
Volume128
DOIs
Publication statusPublished - 15 Apr 2017
MoE publication typeA1 Journal article-refereed

Keywords

  • Hydrogen embrittlement
  • Nickel alloys
  • Positron annihilation spectroscopy
  • Vacancies

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