Pre-strain effects on critical stress and hydrogen content for hydrogen-induced quasi-cleavage fracture in a TRIP-aided bainitic ferrite steel: Martensitic transformation, matrix damage, and strain aging

Kumai, Bakuya; Hojo, Tomohiko; Koyama, Motomichi; Akiyama, Eiji; Waki, Hiroyuki; Nagasaka, Akihiko

doi:10.1016/j.ijhydene.2020.07.036

Cited by 19 publications

(24 citation statements)

References 35 publications

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“…A recent concern with respect to TBF steels is the susceptibility to hydrogen embrittlement, similar to other high-strength metals, such as martensitic and dual phase steels. 8) According to a previous study, 9) the hydrogen embrittlement of TBF steels occurs via transgranular cracking in fresh martensite formed from retained austenite. The cause of cracking is the supersaturation of hydrogen in the fresh martensite owing to the difference in hydrogen solubility between the face-centered cubic and body-centered cubic structures.…”

Section: Introductionmentioning

confidence: 94%

“…9,12) The hydrogen content of the pre-strained specimen was higher than that without pre-strain even under identical hydrogen-charging conditions. 9) In the pre-strained steel, the increase in dislocation density results in trapping more hydrogen and increasing the hydrogen content, 14,15) which can assist transgranular cracking. Moreover, when a large plastic strain was provided, the retained austenite almost disappeared.…”

Section: Introductionmentioning

confidence: 97%

“…Specifically, pre-strain, which induces martensitic transformation before the test, can suppress the occurrence of hydrogen embrittlement. 9,12,13) However, it is also noteworthy that hydrogen embrittlement in TBF steel occurred even after large pre-straining when the diffusible hydrogen content increased. 9,12) The hydrogen content of the pre-strained specimen was higher than that without pre-strain even under identical hydrogen-charging conditions.…”

Section: Introductionmentioning

confidence: 99%

“…9,12,13) However, it is also noteworthy that hydrogen embrittlement in TBF steel occurred even after large pre-straining when the diffusible hydrogen content increased. 9,12) The hydrogen content of the pre-strained specimen was higher than that without pre-strain even under identical hydrogen-charging conditions. 9) In the pre-strained steel, the increase in dislocation density results in trapping more hydrogen and increasing the hydrogen content, 14,15) which can assist transgranular cracking.…”

Section: Introductionmentioning

confidence: 99%

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Roles of Hydrogen Content and Pre-strain on Damage Evolution of TRIP-aided Bainitic Ferrite Steel

et al. 2021

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From the aspect of crack/void initiation and growth characteristics, the effects of pre-strain on the hydrogen embrittlement resistance of a transformation-induced plasticity-aided bainitic ferrite steel were examined. The hydrogen uptake in the specimens without pre-strain caused degradation of crack growth resistance, but the crack initiation probability did not change significantly. It is noteworthy that the degree of degradation was independent of the hydrogen content in the present hydrogen charging condition. Pre-straining to 3% and 6% improved the crack growth resistance of the hydrogen-charged specimens because of a reduction in the probability of austenite presence at the crack tip. Furthermore, a high level of pre-strain provided high hydrogen concentration and resulted in strain-age-hardening, which caused an acceleration of quasi-cleavage fracture, an increase in yield strength, and a stress/strain concentration associated with Lüders deformation. These factors diminished the crack initiation resistance and crack growth resistance.

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Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Roles of Hydrogen Content and Pre-strain on Damage Evolution of TRIP-aided Bainitic Ferrite Steel

et al. 2021

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“…It has been reported that the increase of dislocation density due to the introduction of plastic strain leads to the increase of hydrogen content because the dislocations act as hydrogen trapping sites. 23,25) Therefore, it is considered that the difference of the diffusible hydrogen contents depending on the position was caused by the difference in the degree of plastic strain in the stretch-forming, namely, the density of hydrogen trapping sites. The distribution of the equivalent plastic strain obtained by means of FEM will be discussed later.…”

Section: Hydrogen Embrittlement Crack Initiation Andmentioning

confidence: 99%

Effects of Residual Stress on Hydrogen Embrittlement of a Stretch-Formed Tempered Martensitic Steel Sheet

et al. 2021

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The effects of residual stress on the hydrogen embrittlement behavior of a tempered martensitic steel sheet with 1-GPa-class tensile strength stretch-formed by a hemisphere punch simulating press-formed automotive structural parts were investigated. Cracking on the stretch-formed specimen induced by potentiostatic hydrogen charging was initiated in the foot of the impression of the specimen and propagated to the radial direction both toward the hillside and the plain. The mixture of quasi cleavage and intergranular fractures were observed whole through the fracture surface. Residual stress in the stretch-formed specimens was analyzed by using energy-dispersive X-ray diffraction method utilizing the synchrotron X-ray radiation at SPring-8. In addition, stress and plastic strain distributions in the specimen were analyzed by using Finite Element Method (FEM). These analyses depicted that the high tensile stress in the circumferential direction was in the foot of the impression, corresponding to the direction of the crack growth. The FEM analysis revealed that the high triaxial stress was in the foot suggesting accumulation of hydrogen. It was considered that the preferential crack initiation at the foot was promoted by the high residual stress in the circumferential direction and the hydrogen accumulation due to stress-induced diffusion.

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Experimental and Fractographic Study of the Hydrogen‐Induced Cracking of 45CrNiMoVA Martensitic Advanced High‐Strength Steel

Li,

Liu

2024

steel research int.

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Hydrogen‐induced cracking (HIC) in high‐strength 45CrNiMoVA steel is investigated using smooth and notched cylindrical specimens by performing uniaxial tensile tests. Specimens with different notch geometries are used to analyze the interacting effects of the stress concentration factor and HIC micromechanism. The results show that hydrogen charging reduces the elongation at fracture and the ultimate tensile strength of smooth tensile specimens. The microscopic fracture mode changes from ductile dimples with some quasicleavage fracture without hydrogen to a mixture of brittle quasicleavage and intergranular cracking with hydrogen. For notched specimens with a lower notch root radius, significant stress concentration occurs at the notch root, which enriches hydrogen in these highly stressed regions. This causes a lower notch tensile strength and greater susceptibility to hydrogen embrittlement. Microfracture observations show that the area fraction of the intergranular cracking surface increases gradually, and the brittle zone moves farther away from the notch root upon decreasing the notch root radius, causing the embrittlement index to remain high. These results will help determine the applicability of existing steel for hydrogen service and also provide guidance for developing new high‐strength martensitic steels that can resist hydrogen embrittlement.

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Pre-strain effects on critical stress and hydrogen content for hydrogen-induced quasi-cleavage fracture in a TRIP-aided bainitic ferrite steel: Martensitic transformation, matrix damage, and strain aging

Cited by 19 publications

References 35 publications

Roles of Hydrogen Content and Pre-strain on Damage Evolution of TRIP-aided Bainitic Ferrite Steel

Roles of Hydrogen Content and Pre-strain on Damage Evolution of TRIP-aided Bainitic Ferrite Steel

Effects of Residual Stress on Hydrogen Embrittlement of a Stretch-Formed Tempered Martensitic Steel Sheet

Experimental and Fractographic Study of the Hydrogen‐Induced Cracking of 45CrNiMoVA Martensitic Advanced High‐Strength Steel

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