Macroscopic to nanoscopic in situ investigation on yielding mechanisms in ultrafine grained medium Mn steels: Role of the austenite-ferrite interface

Sun, Binhan; Ma, Yan; Vanderesse, Nicolas; Varanasi, Rama Srinivas; Song, Weijie; Bocher, Philippe; Ponge, Dirk; Raabe, Dierk

doi:10.1016/j.actamat.2019.07.043

Cited by 106 publications

(75 citation statements)

References 64 publications

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“…With respect to the grain size effect on the TRIP effect, contradictory observations have been reported in the literature. While most studies show that smaller grain size suppresses the TRIP effect (i.e., increases austenite's mechanical stability), [129,143,144] the non-effective or even decreasing role of grain refinement on austenite's mechanical stability has been documented. [135,145] These inconsistent results are in part due to the difficulty of deconvoluting the direct effect of austenite grain size from other microstructural and micromechanical factors (e.g., phase constituents, composition, grain morphology, defect density, and stress/ strain partitioning).…”

Section: Thermodynamics Of Segregation At Lattice Defectsmentioning

confidence: 99%

“…[129,144] For the case of strain-induced martensite, some observations show that its nucleation is preferably occurring at various interacting shear systems consisting of e-martensite, stacking fault bundles, or mechanical twins. [143,146] In this context, the number of these intersection sites among crossing shear systems might be reduced by grain refinement, thus the nucleation sites for martensite are decreased. On the other hand, Matsuoka et al [145] found that deformation-induced martensite formation tended to result in the most advantageous martensite variants (near single-variant transformation), in order to release the unidirectional tensile strain.…”

Section: Thermodynamics Of Segregation At Lattice Defectsmentioning

confidence: 99%

“…[147] Among all the AHSS grades, discontinuous yielding is most frequently reported in medium-Mn steels which are cold rolled and intercritically annealed. [143,194] The typical microstructure of these steels consists of ultrafine grained austenite and ferrite with a globular grain morphology. Sun et al [143] have recently shown that the austenite-ferrite interfaces acted as preferential nucleation sites for dislocations in both ferrite and austenite, which suggests that the ultrafine grain size should play a significant role in the occurrence of discontinuous yielding in these types of steels.…”

Section: E Yielding Mechanisms and Serrated Flow In Advanced High-stmentioning

confidence: 99%

“…The unpinned mobile dislocations in ferrite can thus provide the initial plastic flow, which is considered as one important reason for the continuous yielding and initial high work-hardening rate in DP steels. [97] The other example derives from some recent observations by Sun et al, [143] who investigated the initiation of plastic flow in an ultrafine grained medium-Mn steel with an almost fully recrystallized austenite and ferrite microstructure. They observed that under loading, phase boundaries acted as preferable nucleation sites for both, new partial dislocations in austenite, and full dislocations in ferrite.…”

Section: F the Role Of Phase Boundaries In Advanced High-strength Stmentioning

confidence: 99%

“…15-(a) EBSD image quality (IQ) map and calculated distribution of GNDs in a ferrite-martensite dual-phase (DP) steel [97] ; (b) in situ three-point bending tests combined with ECCI, showing dislocation emission at austenite-ferrite phase boundaries in an ultrafine grained duplex medium-Mn steel, reconstructed with permission from Ref. [143] (D2, D3: deformation stage 2 and 3; SFs: stacking faults).…”

Section: Effects Of Boron On Phase Transformationmentioning

confidence: 99%

See 4 more Smart Citations

Current Challenges and Opportunities in Microstructure-Related Properties of Advanced High-Strength Steels

Raabe

Sun

Silva

et al. 2020

Metall Mater Trans A

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125

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This is a viewpoint paper on recent progress in the understanding of the microstructure–property relations of advanced high-strength steels (AHSS). These alloys constitute a class of high-strength, formable steels that are designed mainly as sheet products for the transportation sector. AHSS have often very complex and hierarchical microstructures consisting of ferrite, austenite, bainite, or martensite matrix or of duplex or even multiphase mixtures of these constituents, sometimes enriched with precipitates. This complexity makes it challenging to establish reliable and mechanism-based microstructure–property relationships. A number of excellent studies already exist about the different types of AHSS (such as dual-phase steels, complex phase steels, transformation-induced plasticity steels, twinning-induced plasticity steels, bainitic steels, quenching and partitioning steels, press hardening steels, etc.) and several overviews appeared in which their engineering features related to mechanical properties and forming were discussed. This article reviews recent progress in the understanding of microstructures and alloy design in this field, placing particular attention on the deformation and strain hardening mechanisms of Mn-containing steels that utilize complex dislocation substructures, nanoscale precipitation patterns, deformation-driven transformation, and twinning effects. Recent developments on microalloyed nanoprecipitation hardened and press hardening steels are also reviewed. Besides providing a critical discussion of their microstructures and properties, vital features such as their resistance to hydrogen embrittlement and damage formation are also evaluated. We also present latest progress in advanced characterization and modeling techniques applied to AHSS. Finally, emerging topics such as machine learning, through-process simulation, and additive manufacturing of AHSS are discussed. The aim of this viewpoint is to identify similarities in the deformation and damage mechanisms among these various types of advanced steels and to use these observations for their further development and maturation.

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Section: Thermodynamics Of Segregation At Lattice Defectsmentioning

confidence: 99%

Section: Thermodynamics Of Segregation At Lattice Defectsmentioning

confidence: 99%

Section: E Yielding Mechanisms and Serrated Flow In Advanced High-stmentioning

confidence: 99%

Section: F the Role Of Phase Boundaries In Advanced High-strength Stmentioning

confidence: 99%

Section: Effects Of Boron On Phase Transformationmentioning

confidence: 99%

See 3 more Smart Citations

Current Challenges and Opportunities in Microstructure-Related Properties of Advanced High-Strength Steels

Raabe

Sun

Silva

et al. 2020

Metall Mater Trans A

Self Cite

125

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Characterization and Analysis of Plastic Instability in an Ultrafine‐Grained Medium Mn TRIP Steel

Teng

Pramanik

et al. 2022

Adv Eng Mater

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Herein, the mechanical and magnetic behavior of an ultrafine‐grained (UFG) medium manganese (Mn) transformation‐induced plasticity (TRIP) steel is focused on in its plastic instability. The in situ methods of digital image correlation (DIC) and magnetic Barkhausen noise (MBN) are used to macroscopically characterize the propagation of the Lüders band (stretcher–strain marks) and the evolution of MBN activities during quasistatic tensile deformation. The evolution of microstructure during the plastic instability is investigated ex situ using X‐Ray diffraction (XRD) and transmission electron microscopy (TEM) for selected plastic strain states. It is showed in the results that the plastic instability of this steel is associated with an increase of hardness and enrichment of dislocation density, which can also amplify the MBN signal, while the derived coercivity behaves reversely on an overall trend due to work hardening. The different stress response of the medium Mn steel is closely related to the kinetic martensite microstructure, which in turn modifies the domain–structure response. Thus, the MBN can be used as a potential means for nondestructive evaluation (NDE) for the strengthening of the UFG medium Mn TRIP steel.

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Enhanced Mechanical Properties of a Low‐Carbon Martensitic Steel by Thermally Stable Ni‐Rich Austenite

Kan

Tuo

et al. 2021

steel research int.

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A multistep quench−lamellarization−tempering treatment (QLT) is designed for a low‐carbon high‐Ni martensitic steel to obtain extra high strength, low yield‐to‐tensile ratio, and extra high cryogenic toughness. A mixed microstructure composed of intercritical ferrite, tempered martensite, and Ni‐rich retained austenite (RA) is obtained under the QLT treatment process. The volume fraction of Ni‐rich RA is 13.6% in the QL655T sample. The QL655T sample has a yield strength of 915 MPa and tensile strength of 1080 MPa, leading to a lower yield‐to‐tensile ratio of 0.85. In addition, a total elongation to failure of 19.9% and Charpy impact toughness of 190 J at −196 °C are encouraging in comparison with the conventional counterparts. During tensile deforming, the blocky RA grains can transform easily with increasing strain, while the strain leads to rotations of the film‐like RA grains before the transformation. The RA grains with high thermal stability are attributed to the enrichment of Ni and the effect of size, which makes the ≈11.6% RA grains remain at −196 °C in the QL655T sample. During impact, the transformation‐induced plasticity (TRIP) effect of RA leads to the excellent cryogenic toughness of the QL655T sample.

show abstract

Macroscopic to nanoscopic in situ investigation on yielding mechanisms in ultrafine grained medium Mn steels: Role of the austenite-ferrite interface

Cited by 106 publications

References 64 publications

Current Challenges and Opportunities in Microstructure-Related Properties of Advanced High-Strength Steels

Current Challenges and Opportunities in Microstructure-Related Properties of Advanced High-Strength Steels

Characterization and Analysis of Plastic Instability in an Ultrafine‐Grained Medium Mn TRIP Steel

Enhanced Mechanical Properties of a Low‐Carbon Martensitic Steel by Thermally Stable Ni‐Rich Austenite

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