Do voids nucleate at grain boundaries during ductile rupture? [Do voids initiate at grain boundaries during ductile rupture?]

doi:10.1016/j.actamat.2017.07.004

Title: Do voids nucleate at grain boundaries during ductile rupture? [Do voids initiate at grain boundaries during ductile rupture?]

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Abstract

In the absence of pre-existing failure-critical defects, the fracture or tearing process in deformable metals loaded in tension begins with the nucleation of internal cavities or voids in regions of elevated triaxial stress. While ductile rupture processes initiate at inclusions or precipitates in many alloys, nucleation in pure metals is often assumed to be associated with grain boundaries or triple junctions. This study presents ex situ observations of incipient, subsurface void nucleation in pure tantalum during interrupted uniaxial tensile tests using electron channeling contrast (ECC) imaging, electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM). Instead of forming at grain boundaries, voids initiated at and grew along dislocation cell and cell block boundaries created by plastic deformation. Most of the voids were associated with extended, lamellar deformation-induced boundaries that run along the traces of the {110} or {112} planes, though a few voids initiated at low-angle dislocation subgrain boundaries. In general, a high density of deformation-induced boundaries was observed near the voids. TEM and TKD demonstrate that voids initiate at and grow along cell block boundaries. Two mechanisms for void nucleation in pure metals, vacancy condensation and stored energy dissipation, are discussed in light of thesemore »« less

Authors:

Noell, Philip ^[1]; Carroll, Jay ^[1]; Hattar, Khalid ^[1]; Clark, Blythe ^[1]; Boyce, Brad ^[1]

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Publication Date:: 2017-07-12

Research Org.:: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:: USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:: 1465810

Report Number(s):: SAND-2017-4790J
Journal ID: ISSN 1359-6454; 666530

Grant/Contract Number:: AC04-94AL85000

Resource Type:: Journal Article: Accepted Manuscript

Journal Name:: Acta Materialia

Additional Journal Information:: Journal Volume: 137; Journal Issue: C; Journal ID: ISSN 1359-6454

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; Ductile fracture; Cavity nucleation; Deformation structure; Fracture mechanisms; Void growth

Citation Formats


                    Noell, Philip, Carroll, Jay, Hattar, Khalid, Clark, Blythe, and Boyce, Brad. Do voids nucleate at grain boundaries during ductile rupture? [Do voids initiate at grain boundaries during ductile rupture?].  United States: N. p., 2017. 
        Web.  doi:10.1016/j.actamat.2017.07.004.

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                    Noell, Philip, Carroll, Jay, Hattar, Khalid, Clark, Blythe, & Boyce, Brad. Do voids nucleate at grain boundaries during ductile rupture? [Do voids initiate at grain boundaries during ductile rupture?].  United States.  doi:10.1016/j.actamat.2017.07.004.

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                    Noell, Philip, Carroll, Jay, Hattar, Khalid, Clark, Blythe, and Boyce, Brad. Wed .  
        "Do voids nucleate at grain boundaries during ductile rupture? [Do voids initiate at grain boundaries during ductile rupture?]".  United States.  doi:10.1016/j.actamat.2017.07.004.  https://www.osti.gov/servlets/purl/1465810.

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@article{osti_1465810,

  title        = {Do voids nucleate at grain boundaries during ductile rupture? [Do voids initiate at grain boundaries during ductile rupture?]},

  author       = {Noell, Philip and Carroll, Jay and Hattar, Khalid and Clark, Blythe and Boyce, Brad},

  abstractNote = {In the absence of pre-existing failure-critical defects, the fracture or tearing process in deformable metals loaded in tension begins with the nucleation of internal cavities or voids in regions of elevated triaxial stress. While ductile rupture processes initiate at inclusions or precipitates in many alloys, nucleation in pure metals is often assumed to be associated with grain boundaries or triple junctions. This study presents ex situ observations of incipient, subsurface void nucleation in pure tantalum during interrupted uniaxial tensile tests using electron channeling contrast (ECC) imaging, electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM). Instead of forming at grain boundaries, voids initiated at and grew along dislocation cell and cell block boundaries created by plastic deformation. Most of the voids were associated with extended, lamellar deformation-induced boundaries that run along the traces of the {110} or {112} planes, though a few voids initiated at low-angle dislocation subgrain boundaries. In general, a high density of deformation-induced boundaries was observed near the voids. TEM and TKD demonstrate that voids initiate at and grow along cell block boundaries. Two mechanisms for void nucleation in pure metals, vacancy condensation and stored energy dissipation, are discussed in light of these results. In conclusion, the observations of the present investigation suggest that voids in pure materials nucleate by vacancy condensation and subsequently grow by consuming dislocations.},

  doi          = {10.1016/j.actamat.2017.07.004},

  journal      = {Acta Materialia},

  issn         = {1359-6454},

  number       = C,

  volume       = 137,

  place        = {United States},

  year         = {2017},

  month        = {7}

}

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DOI: 10.1016/j.actamat.2017.07.004

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