Hydrogen Embrittlement of Commercially Produced Advanced High Strength Sheet Steels

Ronevich, Joseph Allen; Speer, John G.; Matlock, David K.

doi:10.4271/2010-01-0447

Cited by 76 publications

(30 citation statements)

References 11 publications

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“…However, in this case, dimple fracture at the PAG boundaries has also been observed [58], as opposed to the fragile failure at the nucleation stage observed in nanostructured bainite. In TRIP-assisted steels, on the other hand, it is known that the mechanical stability of the austenite is a critical factor on crack propagation, since the brittle martensite increases the susceptibility to hydrogen embrittlement [59][60][61][62] Figure 6. The straight line in Figure 6 represents the Considere´s equation, p = n; i.e., when the curves cross the straight line, the localization of the yielding starts and thus plastic deformation leaves the uniform region.…”

Section: Ductility: Work-hardening and Fracture Mechanisms In Nanostrmentioning

confidence: 99%

“…to the fragile failure at the nucleation stage observed in nanostructured bainite. In TRIP-assisted steels, on the other hand, it is known that the mechanical stability of the austenite is a critical factor on crack propagation, since the brittle martensite increases the susceptibility to hydrogen embrittlement [59][60][61][62].…”

Section: Ductility: Work-hardening and Fracture Mechanisms In Nanostrmentioning

confidence: 99%

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Ductility of Nanostructured Bainite

Morales-Rivas

García‐Mateo

Sourmail³

et al. 2016

Metals

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Nanostructured bainite is a novel ultra-high-strength steel-concept under intensive current research, in which the optimization of its mechanical properties can only come from a clear understanding of the parameters that control its ductility. This work reviews first the nature of this composite-like material as a product of heat treatment conditions. Subsequently, the premises of ductility behavior are presented, taking as a reference related microstructures: conventional bainitic steels, and TRIP-aided steels. The ductility of nanostructured bainite is then discussed in terms of work-hardening and fracture mechanisms, leading to an analysis of the three-fold correlation between ductility, mechanically-induced martensitic transformation, and mechanical partitioning between the phases. Results suggest that a highly stable/hard retained austenite, with mechanical properties close to the matrix of bainitic ferrite, is advantageous in order to enhance ductility.Keywords: nanostructured bainite; ductility; microstructure; mechanical properties Nanostructured Bainite: Heat-Treatments and MicrostructureThere is an increasing interest in nanocrystalline steels because of their unique mechanical properties, achieving ultra-high strength while maintaining good values of ductility [1,2]. However, the manufacture of nanocrystalline steels is frequently very cost-consuming, involving the addition of expensive alloying elements, severe plastic deformation or complex thermomechanical routes in order to obtain the desired refinement of the microstructure during the material processing. A new generation of steels, nanostructured bainitic steels, is one promising solution because of the simplicity in terms of alloy design and processing. On the one hand, they are low-alloyed steels, with a typical chemical composition range being: (0.6-1)C-(≥1.5)Si-(0.7-2)Mn-(0.4-1.7)Cr-(0-0.2)Mo wt % [3]. On the other hand, the heat treatment consists of complete austenitization followed by isothermal holding at temperature T as low as T/T m < 0.25, where T m is the absolute melting temperature. The transformation itself leads to the nanocrystalline structure without further technological efforts, and has received much attention in recent years [4][5][6][7]. These novel microstructures have achieved the highest strength-toughness combinations ever recorded in bainitic steels (2.2 GPa-30 MPa·m 1/2 ) [8][9][10][11].The microstructure of nanostructured bainite consists basically of two phases: a hard matrix of bainitic ferrite and a carbon-enriched retained austenite, the second dispersed phase. It is characterized by the lack of coarse precipitates of cementite, due to the addition of Si with resulting content of near

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Section: Ductility: Work-hardening and Fracture Mechanisms In Nanostrmentioning

confidence: 99%

Section: Ductility: Work-hardening and Fracture Mechanisms In Nanostrmentioning

confidence: 99%

Ductility of Nanostructured Bainite

Morales-Rivas

García‐Mateo

Sourmail³

et al. 2016

Metals

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“…Lacroix et al [23] investigated the fracture behavior of TRIP steels in an inert environment and found that crack initiation was always related to the presence of martensite. Ronevich et al [24] observed that crack initiation occurs at martensitic regions and further propagation into ferrite takes place in TRIP steel charged with hydrogen, while in uncharged TRIP steel microcracks were found in martensite without further propagation into the ferrite. Similar observations were made by Koyama et al [25] for dualphase steel.…”

Section: Introductionmentioning

confidence: 98%

Characterization of hydrogen induced cracking in TRIP-assisted steels

Laureys

Depover

Petrov

et al. 2015

International Journal of Hydrogen Energy

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“…Some of the initial momentum towards exploitation in the automotive industry was jeopardized by reports of delayed fracture in formed components, an effect often attributed to hydrogen [3,4]. Given that austenitic steels do not generally suffer from hydrogen embrittlement [5][6][7][8], one interpretation is that the formation of α martensite during forming operations is necessary for the onset of delayed fracture in Fe-16Mn-0.6C wt% [3]. However, an alloy much more resistant to martensitic transformation, with composition Fe-22Mn-0.6C wt% also exhibited static fracture after cup forming and exposure to air for 7 days; in this case, the failure was attributed to localized deformation and twinning [4].…”

Section: Introductionmentioning

confidence: 99%

Effect of aluminium on hydrogen-induced fracture behaviour in austenitic Fe–Mn–C steel

et al. 2013

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It is known empirically that the addition of aluminium as a solute in high-Mn austenitic steels dramatically improves their resistance to hydrogen-induced embrittlement. A variety of experimental techniques, including the characterization of trapping sites and high-resolution observation of fracture facets, have been used to reveal the mechanism by which aluminium induces this effect. It is found that transgranular fracture is promoted by the segregation of hydrogen to mechanical twin interfaces and to any -martensite that is induced during deformation. Because aluminium increases the stacking fault energy of austenite, the tendency for mechanical twinning is reduced, and the formation of deformationinduced martensite eliminated. These two effects contribute to the resistance of the aluminium-alloyed steel to hydrogen embrittlement.

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Hydrogen Embrittlement of Commercially Produced Advanced High Strength Sheet Steels

Cited by 76 publications

References 11 publications

Ductility of Nanostructured Bainite

Ductility of Nanostructured Bainite

Characterization of hydrogen induced cracking in TRIP-assisted steels

Effect of aluminium on hydrogen-induced fracture behaviour in austenitic Fe–Mn–C steel

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