Investigation on the deformation mechanisms and size-dependent hardening effect of He bubbles in 84 dpa neutron irradiated Inconel X-750

Wang, Qiang; Judge, C. D.; Howard, C.; Mattucci, Mitchell; Rajakumar, Heygaan; Hoendermis, Seanna; Dixon, C.E.; Daymond, Mark R.; Bickel, G. A.

doi:10.1016/j.nme.2021.101025

Cited by 5 publications

(15 citation statements)

References 30 publications

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“…Based on observations of bands of sheared cavities such as those shown in Figure 19, Howard et al state that the "mechanism of crack initiation via dislocation channel formation and subsequent bubble elongation and shear" is responsible for transgranular fracture. However, the cracking reported by Howard et al [73], and also by Wang et al [93] working on the same material, is not parallel to {111}. The conditions for channeling also did not apply as there was no evidence shown for a high density of prismatic dislocation loops that would promote channeling [93].…”

Section: Transgranular Fracturementioning

confidence: 90%

“…However, the cracking reported by Howard et al [73], and also by Wang et al [93] working on the same material, is not parallel to {111}. The conditions for channeling also did not apply as there was no evidence shown for a high density of prismatic dislocation loops that would promote channeling [93]. Howard et al concluded, without evidence, that "The currently proposed mechanism of crack initiation is linked with grain interior strain localization (also known as channel fracture), in which helium bubbles become elongated, coalesce, and fracture along linear facets.…”

Section: Transgranular Fracturementioning

confidence: 93%

“…They seemed to imply that planar cracks are created by the overlap of cavities in one direction, but exactly how that creates a planar crack is not clear. An elongated bubble may be considered to be a pencil crack but there is no spatial link between the sheared cavities and the cracks that are actually observed [73,93]. The observations of sheared cavities cited by Howard et al and others [73,[87][88][89][90][91] do not support a crack formation mechanism.…”

Section: Transgranular Fracturementioning

confidence: 98%

“…While one can imagine many different scenarios, proof of the mechanism for crack formation in the plane of a slip band proposed by Howard et al and others [73,[87][88][89][90][91] is lacking. It is noteworthy that channeling was never mentioned in a follow-up publication by the same group [93] describing a detailed TEM examination of the same sample that was deemed to have failed by channel fracture by Howard et al [73 ].…”

Section: Transgranular Fracturementioning

confidence: 99%

“…Because the two studies [73,93] were conducted on the same material, it is possible to make a link between the two. The feature along which cracking was observed and identified as a "slip band or channel" in [73] is shown in Figure 20a.…”

Section: Transgranular Fracturementioning

confidence: 99%

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Strain Localisation and Fracture of Nuclear Reactor Core Materials

Griffiths

2023

JNE

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The production of prismatic dislocation loops in nuclear reactor core materials results in hardening because the loops impede dislocation motion. Yielding often occurs by a localised clearing of the loops through interactions with gliding dislocations called channeling. The cleared channels represent a softer material within which most of the subsequent deformation is localized. Channeling is often associated with hypothetical dislocation pileup and intergranular cracking in reactor components although the channels themselves do not amplify stress as one would expect from a pileup. The channels are often similar in appearance to twins leading to the possibility that twins are sometimes mistakenly identified as channels. Neither twins nor dislocation channels, which are bulk shears, produce the same stress conditions as a pileup on a single plane. At high doses, when cavities are produced (either He-stabilised bubbles at low temperatures or voids at high temperatures), there can be reduced ductility because the material is already in an equivalent advanced stage of microscopic necking. He-stabilised cavities form preferentially on grain boundaries and at precipitate or incoherent twin/ε-martensite interfaces. The higher planar density of the cavities, coupled with the incompatibility at the interface, results in a preferential failure known as He embrittlement. Strain localisation and inter- or intragranular failure are dependent on many factors that are ultimately microstructural in nature. The mechanisms are described and discussed in relation to reactor core materials.

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Section: Transgranular Fracturementioning

confidence: 90%