A high-strength heterogeneous structural dual-phase steel

Gao, Bo; Chen, Xuefei; Pan, Zhiyi; Li, Jiansheng; Ma, Ying; Cao, Yang; Liu, Manping; Lai, Qingquan; Xiao, Lirong; Zhou, Hao

doi:10.1007/s10853-019-03785-1

Cited by 58 publications

(17 citation statements)

References 59 publications

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“…After holding at 740, 760, 780, and 800 • C for a long time, 36%, 48%, 65%, and 85% reverse austenite was obtained, respectively. Heterogeneous microstructure with hard and soft phases is characterized by microstructural heterogeneity and/or compositional heterogeneity, which lead to a dramatic difference in strength between different structures [4,[6][7][8]. The strength mismatch between different structures will cause the inhomogeneous deformation in local areas, by which a strain gradient around the interfaces could be triggered, and geometrically necessary dislocations (GNDs) could build up.…”

Section: Methodsmentioning

confidence: 99%

“…Accordingly, the steels with higher martensite fraction (IA780 and IA800) showed higher back stress. The effective stress is closely related to the forest hardening in intercritical ferrite [7]. The plastic strain will be more concentrated in the intercritical ferrite during the tensile test, and more dislocations are thus generated in this microconstituent.…”

Section: Analysis Of Mechanical Behavior 421 Strength and Work Harden...mentioning

confidence: 99%

“…As a result, the b value increased and the N value decreased, resulting in the increase in the ln(b/N 2 ) value and yield ratio. It can be inferred that the reduction of the yield ratio can be achieved through modifying the fraction of martensite in the heterogeneous microstructure by decreasing the value of b or increasing the value of N. With the increase in annealing temperature, the fraction of martensite in the matrix gradually increased, and the combination of strength and ductility was significantly improved, which is related to the simultaneous enhancement of back stress and effective stress [7]. The back stress originates from the stress partitioning due to the strength mismatch between intercritical ferrite and martensite [22,37], and the deformation heterogeneity will be enhanced with the increase in martensite fraction in the matrix.…”

Section: Yield Ratiomentioning

confidence: 99%

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Tailoring Heterogeneous Microstructure in a High-Strength Low-Alloy Steel for Enhanced Strength-Toughness Balance

Gao

et al. 2021

Metals

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The attainment of both strength and toughness is of vital importance to most structural materials, although unfortunately they are generally mutually exclusive. Here, we report that simultaneous increases in strength and toughness in a high-strength low-alloy (HSLA) steel were achieved by tailoring the heterogeneous microstructure consisting of soft intercritical ferrite and hard martensite via intercritical heat treatment. The heterogeneous microstructure features were studied from the perspective of morphology and crystallography to uncover the effect on mechanical properties. Specifically, the volume fraction of martensite increased with increasing annealing temperature, which resulted in increased back stress and effective stress, and thereby an improved strength-ductility combination. The enrichment of carbon and alloying elements in the martensite was lowered with the increase in annealing temperature. As a result, the hardness difference between the intercritical ferrite and martensite was reduced. In addition, the globular reversed austenite preferentially grew into the adjacent austenite grain that held no Kurdjumov-Sachs (K-S) orientation relationship with it, which effectively refined the coarse prior austenite grains and increased the density of high angle grain boundaries. The synergy of these two factors contributed to the improved low-temperature toughness. This work demonstrates a strategy for designing heterostructured HSLA steels with superior mechanical properties.

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Section: Methodsmentioning

confidence: 99%

Section: Analysis Of Mechanical Behavior 421 Strength and Work Harden...mentioning

confidence: 99%

Section: Yield Ratiomentioning

confidence: 99%

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Tailoring Heterogeneous Microstructure in a High-Strength Low-Alloy Steel for Enhanced Strength-Toughness Balance

Gao

et al. 2021

Metals

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“…In contrary to the observed deformation behaviour as homogeneous in a macroscopic viewpoint, multiphase material actually experiences deformation inhomogeneity through strain partitioning among the constituent phases. 34–36 Stanford et al 37 also show the strain partitioning behaviour in multiphase steel under cyclic loading, where it was observed that the plastic strain accumulation is predominant in ferrite instead of bainite. Besides strain partitioning between constituent phases, a variation in crystallographic misorientation, GND and slip occur while having an exposure at different degrees of cyclic plastic strain in individual grain.…”

Section: Introductionmentioning

confidence: 98%

Effect of microstructural constituents and morphological characteristics on low cycle fatigue behaviour of inter-critically annealed 20MnMoNi55 steel

Basu

Acharyya

Sahoo

2021

Proceedings of the Institution of Mechanical Engineers, Part L:

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The effect of varying microstructural parameters on the cyclic behaviour of dual-phase steels was studied on the basis of experimental and micromechanical finite-element simulated results. The initial bainitic morphology of as-received 20MnMoNi55 steel was transformed into ferrite and martensite through proper inter-critical heat treatment procedures. Strain-controlled low cycle fatigue tests were conducted at room temperature with different strain amplitudes at a specific strain rate of 10−3/s. The cyclic stress–strain curve, obtained through joining the peak stresses of hysteresis loops corresponding to different strain amplitude, shows an increase in strain hardening with an increase in volume fraction of martensite. Whereas the rate of cyclic softening, considering the decrease in stress amplitude with respect to elapsed cycles, increases with increasing strain amplitude. Inclusive of all affecting microstructural parameters, an original microstructure-based representative volume element associated with a crystal plasticity-based material model was adopted for conducting micromechanical finite-element simulation. In addition to several parameters associated with a crystal plasticity model, consideration of initial geometrically necessary dislocation density in constituent phases resulted in the accurate prediction of a hysteresis loop at low strain amplitude as compared with the experimental results. A variation of stress triaxiality built up in ferrite matrix with martensite fraction along with deformation inhomogeneity between ferrite and martensite was also observed through a strain partitioning phenomenon obtained from finite-element simulated results.

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“…Creating a heterogeneous microstructure in HSLA steels has proven to be a new method of addressing the above problem [8][9][10][11]. Heterogeneous microstructure has a significant difference in strength among different domains, generally containing a hard martensite phase embedded in the soft austenite and/or ferrite matrix [12][13], which can be fabricated by intercritical annealing [14][15]. Compared with conventional Q&T processing, intercritical annealing can markedly increase the ductility and toughness and lower the YR of low carbon low alloy steels.…”

Section: Introductionmentioning

confidence: 99%

Determining role of heterogeneous microstructure in lowering yield ratio and enhancing impact toughness in high-strength low-alloy steel

Gao

et al. 2021

Int J Miner Metall Mater

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Here we present a novel approach of intercritical heat treatment for microstructure tailoring, in which intercritical annealing is introduced between conventional quenching and tempering. This induced a heterogeneous microstructure consisting of soft intercritical ferrite and hard tempered martensite, resulting in a low yield ratio (YR) and high impact toughness in a high-strength low-alloy steel. The initial yielding and subsequent work hardening behavior of the steel during tensile deformation were modified by the presence of soft intercritical ferrite after intercritical annealing, in comparison to the steel with full martensitic microstructure. The increase in YR was related to the reduction in hardness difference between the soft and hard phases due to the precipitation of nano-carbides and the recovery of dislocations during tempering. The excellent low-temperature toughness was ascribed not only to the decrease in probability of microcrack initiation for the reduction of hardness difference between two phases, but also to the increase in resistance of microcrack propagation caused by the high density of high angle grain boundaries.

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A high-strength heterogeneous structural dual-phase steel

Cited by 58 publications

References 59 publications

Tailoring Heterogeneous Microstructure in a High-Strength Low-Alloy Steel for Enhanced Strength-Toughness Balance

Tailoring Heterogeneous Microstructure in a High-Strength Low-Alloy Steel for Enhanced Strength-Toughness Balance

Effect of microstructural constituents and morphological characteristics on low cycle fatigue behaviour of inter-critically annealed 20MnMoNi55 steel

Determining role of heterogeneous microstructure in lowering yield ratio and enhancing impact toughness in high-strength low-alloy steel

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