Effect of low-pressure hydrogen on the room-temperature tensile ductility and fracture behavior of Ni3Al

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • J. W. Cohron
  • E. P. George
  • L. Heatherly
  • C. T. Liu
  • R. H. Zee

Detail(s)

Original languageEnglish
Pages (from-to)497-502
Journal / PublicationIntermetallics
Volume4
Issue number6
Publication statusPublished - Sep 1996
Externally publishedYes

Abstract

The effect of low-pressure (≤1.3 × 103 Pa) hydrogen gas on the ductility and fracture behavior of polycrystalline Ni3Al (23.4 at% Al) was investigated. Room-temperature tensile ductilities remained high over the entire pressure range tested: from 41% elongation to fracture at 5.7 × 10-8 Pa pressure to 31% at 1.3 × 103 Pa. Over this pressure range, the amount of transgranular fracture also remained quite high and scaled with the tensile ductility, increasing from ∼60% in the samples with 31% ductility to ∼70% in the specimen with 41% ductility. The ionization gage - used to measure hydrogen pressure - had a dramatic (deleterious) effect on the ductility of Ni3Al: at any given hydrogen pressure, the ductility measured with the ion gage on was about half to a quarter of that measured with the ion gage turned off. Accompanying this decrease in ductility was a change in fracture mode from predominantly transgranular to predominantly intergranular. The role of the ion gage is believed to be hot-filament-assisted dissociation of molecular H2 into atomic H, which is quickly absorbed and embrittles the crack-tip regions. In the absence of any H-induced embrittlement (either by filament-assisted dissociation of H2 or by Al-induced reduction of H2O), polycrystalline Ni3Al is found to be quite ductile, with tensile elongations exceeding 40% and predominantly (>70%) transgranular fracture. Since these ductilities are similar to those of the most ductile B-doped alloys, the main role of boron is to suppress environmental embrittlement. Our results indicate that, at room temperature, low-pressure H2 does not dissociate very efficiently into atomic H on the surfaces of Ni3Al and that, at comparable pressures, hydrogen is not as harmful to ductility as moisture (H2O). Copyright © 1996 Elsevier Science Ltd.

Research Area(s)

  • A. nickel aluminides, B. environmental embrittlement, Based on Ni3Al, Hydrogen embrittlement

Citation Format(s)

Effect of low-pressure hydrogen on the room-temperature tensile ductility and fracture behavior of Ni3Al. / Cohron, J. W.; George, E. P.; Heatherly, L.; Liu, C. T.; Zee, R. H.

In: Intermetallics, Vol. 4, No. 6, 09.1996, p. 497-502.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review