Research ArticleMATERIALS SCIENCE

Hydrogen embrittlement through the formation of low-energy dislocation nanostructures in nanoprecipitation-strengthened steels

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Science Advances  11 Nov 2020:
Vol. 6, no. 46, eabb6152
DOI: 10.1126/sciadv.abb6152
  • Fig. 1 Multiscale depiction of HE.

    (Left) Accepted theories of HELP (hydrogen-enhanced localized plasticity), with strong interaction with dislocations at crack tips; HESIV (hydrogen-enhanced strain-induced vacancy formation), forming clusters of vacancies (voids) at the tips; and HEDE (hydrogen-enhanced decohesion), promoting decohesion. (Right) New mechanism proposed in this work. Hydrogen diffuses to crack tips, where its concentration increases, promoting dislocation cell formation, which, upon reaching a critical level, causes failure.

  • Fig. 2 SEM and TEM micrographs showing the microstructure before charging and dislocation and precipitate structures after charging.

    Ti-Mo and V-Mo (A) before and (B) after charging, and (C) after tensile testing with no and (D) with hydrogen charging.

  • Fig. 3 Ti-Mo mechanical response in the fractured region in hydrogen-free and -charged specimens.

    (A) FIB lamella taken from dislocation nanostructure, highlighting regions 1 and 2, respectively shown in (B) and (C). (D) Region 3 showing TiC/dislocation interaction. (E) Misorientation map around regions 1 and 2, with the corresponding misorientaiton values of line 1 in (F).

  • Fig. 4 V-Mo mechanical response in the fractured region in hydrogen-free and -charged specimens.

    (A) FIB lamella taken from the dislocation nanostructure showing heavily deformed regions 1 and 2 around the crack source, respectively, shown in (B-1) and (C-2). (D-2) shows the heavy misorientation mapped in (C-2). The twin martensite induced by hydrogen is shown in (E). Regions away from the crack source are shown in (F), in (G) and (H) where modest misorientation serrations are shown in the cleavage region.

  • Table 1 Chemical composition of the experimental steels (wt %).

    MaterialCSiMnAlVTiNMo
    Ti-Mo0.10.21.60.0450.2≤10 ppm0.5
    V-Mo0.10.21.60.0450.2≤10 ppm0.5
  • Table 2 Quantitative metallography.

    MaterialDislocation
    density (1013 m−2)
    Precipitate density
    (μm−2)
    Precipitate radius
    (nm)
    Dislocation cell
    size (nm)
    Dislocation
    misorientation (°)
    Residual stress
    (MPa)
    Ti-Mo uncharged5.025505.81201–5−343
    Ti-Mo charged23.917715–35−602
    V-Mo uncharged3.964207.91441–7−347
    V-Mo charged11.619340–60−470
  • Table 3 Computation results.

    MaterialDislocation cell size
    (nm)
    Dislocation
    misorientation (°)
    Ti-Mo uncharged1331.2
    Ti-Mo charged30015.2
    V-Mo uncharged1534.5
    V-Mo charged29154.5

Supplementary Materials

  • Supplementary Materials

    Hydrogen embrittlement through the formation of low-energy dislocation nanostructures in nanoprecipitation-strengthened steels

    P. Gong, J. Nutter, P. E. J. Rivera-Diaz-Del-Castillo, W. M. Rainforth

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