Enhanced ductility and toughness in an ultrahigh-strength Mn–Si–Cr–C steel: The great potential of ultrafine filmy retained austenite

Gao, Guhui; Zhang, Han; Gui, Xuchun; Luo, Peng; Tan, Zhunli; Bai, Bin

doi:10.1016/j.actamat.2014.05.055

Cited by 280 publications

(122 citation statements)

References 36 publications

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“…2c taken from Ref. [29]. The same concept can be applied to martensitic steels to produce duplex microstructures.…”

Section: Bulk Ultrafine Grained and Nanocrystalline Metalsmentioning

confidence: 97%

“…We have added in Fig. 6c the results on UFG-DP steels obtained in [30] for two annealing temperatures and the results on medium C steel [29], see descriptions in Section 2.1.1 The BQ&P treatment applied to the medium C steel and the short anneal applied at 610°C on the low C steel lead to extremely attractive properties. Fig.…”

Section: Fracture Of Bulk Ufg and Nanostructured Metalsmentioning

confidence: 98%

“…Their microstructure may also be met in inter-critically heat-affected zones of multi-pass welds [27]. The process named Q&P, in which Q stands for ''Quench'' and P for ''Partitioning'', involves an initial cooling step to a quenching temperature, T q , such as M f < T q < M S (M S and M f mean the ''start'' and the ''end'' of martensitic transformation, respectively), followed by an isothermal holding at T q or at higher [17]; (b) bimodal structure produced after heat treatment from the microstructure shown in (a); (c) TEM micrographs of the submicron thick film type retained austenite in BAT (see definition on the text) from [29]; (d) High Mn steel with very fine-grained austenite-ferrite (<400 nm) duplex microstructure obtained by combining rolling and intercritical annealing, from [30]; (e) nanotwinned Cu produced by electrodeposition, from [42]; (f) TEM bright field micrograph of a FIB cross section of a 300 nm thick Pd film with 30 nm elongated columnar grains exhibiting a h1 1 1i texture parallel to the normal of the film [51]; (g) TEM bright field micrograph of a 40 nm Cu/40 nm Nb multilayer showing {1 1 1}Cu||{1 1 0}Nb fiber texture [228]. temperature with the purpose of promoting C (and other c stabilizing elements, such as Ni and Mn) transfer from martensite into the austenite.…”

Section: Bulk Ultrafine Grained and Nanocrystalline Metalsmentioning

confidence: 99%

“…The second concept involves only a quenching followed by inter-critical tempering. Gao and co-workers [29] studied three heat treatment routes incorporating bainite formation during quenching, namely bainite-based quenching plus tempering (BQ&T), bainite austempering (BAT) and bainite-based quenching plus partitioning (BQ&P). These heat-treatments were applied to a medium C-Mn-Si-Cr alloyed steel.…”

Section: Bulk Ultrafine Grained and Nanocrystalline Metalsmentioning

confidence: 99%

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Failure of metals III: Fracture and fatigue of nanostructured metallic materials

2016

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a b s t r a c tPushing the internal or external dimensions of metallic alloys down to the nanometer scale gives rise to strong materials, though most often at the expense of a low ductility and a low resistance to cracking, with negative impact on the transfer to engineering applications. These characteristics are observed, with some exceptions, in bulk ultra-fine grained and nanocrystalline metals, nano-twinned metals, thin metallic coatings on substrates and freestanding thin metallic films and nanowires. This overview encompasses all these systems to reveal commonalities in the origins of the lack of ductility and fracture resistance, in factors governing fatigue resistance, and in ways to improve properties. After surveying the various processing methods and key deformation mechanisms, we systematically address the current state of the art in terms of plastic localization, damage, static and fatigue cracking, for three classes of systems: (1) bulk ultra-fine grained and nanocrystalline metals, (2) thin metallic films on substrates, and (3) 1D and 2D freestanding micro and nanoscale systems. In doing so, we aim to favour cross-fertilization between progress made in the fields of mechanics of thin films, nanomechanics, fundamental researches in bulk nanocrystalline metals and metallurgy to impart enhanced resistance to fracture and fatigue in high-strength nanostructured systems. This involves exploiting intrinsic mechanisms, e.g. to enhance hardening and rate-sensitivity so as to delay necking, or improve grain-boundary cohesion to resist intergranular cracks or voids. Extrinsic methods can also be utilized such as by hybridizing the metal with another material to delocalize the deformation -as practiced in stretchable electronics. Fatigue crack initiation is in principle improved by a fine structure, but at the expense of larger fatigue crack growth rates. Extrinsic toughening through hybridization allows arresting or bridging cracks. The content and discussions are based on experimental, theoretical and simulation results from the recent literature, and focus is laid on linking microstructure and physical mechanisms to the overall mechanical behavior.

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“…2c taken from Ref. [29]. The same concept can be applied to martensitic steels to produce duplex microstructures.…”

Section: Bulk Ultrafine Grained and Nanocrystalline Metalsmentioning

confidence: 97%

Section: Fracture Of Bulk Ufg and Nanostructured Metalsmentioning

confidence: 98%

Section: Bulk Ultrafine Grained and Nanocrystalline Metalsmentioning

confidence: 99%

Section: Bulk Ultrafine Grained and Nanocrystalline Metalsmentioning

confidence: 99%

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Failure of metals III: Fracture and fatigue of nanostructured metallic materials

2016

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“…[14,[16][17][18] Moreover, it is commonly thought that the introduction of thermally stable-retained austenite can improve toughness. [19,20] It is hence possible to develop a novel heavy steel plate with enhanced strength, ductility, and low-temperature impact toughness utilizing Mn element. However, it has been recognized that the contribution of metastable-retained austenite to strain hardening capacity and ductility is inconsistent with that to toughness in previous studies, [21,22] showing that the more stable the retained austenite, the more excellent the low-temperature impact toughness is and the poorer the strain hardening capacity and ductility are.…”

Section: Introductionmentioning

confidence: 99%

Influence of Heat Treatments on the Microstructural Evolution and Resultant Mechanical Properties in a Low Carbon Medium Mn Heavy Steel Plate

Chen

Liu

et al. 2016

Metall Mater Trans A

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In this study, the microstructural evolution and resultant mechanical properties in a low carbon medium Mn heavy steel plate were investigated in detail. The results show that the introduction of medium manganese alloy design in the heavy steel plate has been shown to achieve the outstanding combination of strength, ductility, low-temperature impact toughness, and strain hardening capacity. It has been found that the austenite phase mainly displays at martensitic lath boundaries and shows lath shape for the heat treating at 873 K (600°C) for 1 to 10 hours or 893 K (620°C) for 2 hours, and not all the austenite phase obeys the K-S or N-W orientation relationship with respect to abutting martensitic lath. Although the microstructure in the steel after heat treating at 873 K (600°C) for 1 to 10 hours is similar to each other, the resultant mechanical properties are very different because the volume fraction and stability of retained austenite vary with the heat treatments. The best low-temperature impact toughness is achieved after heat treating at 873 K (600°C) for 2 hours due to the formation of a considerable volume fraction of retained austenite with relatively high stability, but the strain hardening capacity and ductility are disappointing because of insufficient TRIP effect. Based on enhancing TRIP effect, the two methods have been suggested. One is to increase the isothermal holding temperature to 893 K (620°C), and the other one is to prolong the isothermal holding time to 10 hours at 873 K (600°C). The two methods can significantly increase strain hardening capacity and ductility nearly without harming low-temperature impact toughness. In addition, the stability of retained austenite has been discussed by the quantitative analysis and it has been demonstrated that the stability of retained austenite is related to the chemical composition, size, and morphology. Moreover, the isothermal holding temperature has a great effect on the stability of retained austenite, while the effect of the isothermal holding time is relatively poor.

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The Role of Transformation‐Induced Plasticity in the Development of Advanced High Strength Steels

Liu

Huang

2018

Adv Eng Mater

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Lightweight structural components made of advanced high-strength steels (AHSSs) in the automotive industry can substantially reduce greenhouse gas emissions. The 3rd-generation AHSSs, which consist of medium Mn steel, quenching and partitioning (Q&P) steel, and carbide-free bainitic (CFB) steel, is the current research focus of the steel community. In particular, the retained austenite grains are the intrinsic components of the 3rd-generation AHSSs. These retained austenite grains can demonstrate a transformationinduced plasticity (TRIP) effect by transforming into martensite during mechanical loading, improving the strain-hardening behavior of AHSSs. Consequently, intensive research has been carried out over the past 30 years to understand the role of the TRIP effect on the development of AHSSs. Therefore, this review article is aimed to provide a state-of-the-art summary of recent progress on AHSSs with the TRIP effect. Specifically, the processing, the relationship between microstructure and mechanical properties, and the potential industrial applications of TRIP-enabled AHSSs will be addressed in this review. More importantly, the mechanical stability of the retained austenite grains, which determines the overall performance of the TRIP effect in AHSSs, will be discussed by considering several governing factors.

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Enhanced ductility and toughness in an ultrahigh-strength Mn–Si–Cr–C steel: The great potential of ultrafine filmy retained austenite

Cited by 280 publications

References 36 publications

Failure of metals III: Fracture and fatigue of nanostructured metallic materials

Failure of metals III: Fracture and fatigue of nanostructured metallic materials

Influence of Heat Treatments on the Microstructural Evolution and Resultant Mechanical Properties in a Low Carbon Medium Mn Heavy Steel Plate

The Role of Transformation‐Induced Plasticity in the Development of Advanced High Strength Steels

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