Effects of grain size and deformation temperature on hydrogen-enhanced vacancy formation in Ni alloys. (15th April 2017)

• Record Type: Journal Article
• Authors: Lawrence, Samantha K.; Yagodzinskyy, Yuriy; Hänninen, Hannu; Korhonen, Esa; Tuomisto, Filip; Harris, Zachary D.; Somerday, Brian P.
• Is Part Of: Acta materialia. Volume 128(2017)
• Page Start: 218
• Page End: 226
• Publication Date: 2017-04-15
• Subjects: Positron annihilation spectroscopy -- Nickel alloys -- Hydrogen embrittlement -- Vacancies; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2017.02.016
• Languages: English
• ISSNs: 1359-6454

Abstract

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. Graphical abstract: Image