Three-dimensional atom probe analysis of boron segregation at austenite grain boundary in a low carbon steel - Effects of boundary misorientation and quenching temperature

Miyamoto, Gorō; Goto, Ai; Takayama, Naoki; Furuhara, Tadashi

doi:10.1016/j.scriptamat.2018.05.046

Cited by 59 publications

(32 citation statements)

References 19 publications

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“…Recently, Myamoto et al [59] using a similar approach as used in this work, also observed that B segregation at γ GBs increases with increasing soaking temperature from 900 to 1050 °C and to 1200 °C. The authors suggest that NES occurs during cooling.…”

Section: Temperature Dependence Of the Boron Distributionsupporting

confidence: 64%

Grain-boundary segregation of boron in high-strength steel studied by nano-SIMS and atom probe tomography

et al. 2020

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High resolution imaging by secondary ion mass spectrometry and atom probe tomography have been employed to investigate boron segregation at austenite grain boundaries (γ GBs) after soaking in a highstrength low-carbon steel. The combined use of these two analytical techniques is shown to be powerful for quantifying solute and segregated boron levels. Quenching was performed after soaking aiming to clarify the temperature effect on boron distribution under thermal equilibrium. Boron depletion in the γ GBs vicinity was observed in the as-quenched states from high temperatures, suggesting that the cooling rate was not fast enough to limit boron diffusion during cooling. We found that boron segregation at γ GBs increases with temperature. This is due to the increase of solute boron concentration in the grains, resulting from boride precipitate dissolution. It appears that the segregation magnitude still follows the equilibrium laws as a function of temperature. From our investigations, it was possible to determine the boron equilibrium segregation enthalpy. These results have important practical consequences for controlling the levels of segregated boron in steels.

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Section: Temperature Dependence Of the Boron Distributionsupporting

confidence: 64%

Grain-boundary segregation of boron in high-strength steel studied by nano-SIMS and atom probe tomography

et al. 2020

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“…[219] Non-equilibrium segregation occurs when a complex of vacancy and segregating atom is formed and diffuse to the vacancy sinks. [220][221][222][223][224][225][226][227] Such type of segregation appears normally when it is quenched from high temperature to low temperature which leads to high oversaturation of vacancies. More recent observations obtained by APT have revealed that segregation is controlled by equilibrium mode with diffusion limitation at lower austenitization temperatures, [220] however, when cooled from higher austenitization temperatures, non-equilibrium segregation dominates.…”

Section: Effects Of Boron On Phase Transformationmentioning

confidence: 99%

“…More recent observations obtained by APT have revealed that segregation is controlled by equilibrium mode with diffusion limitation at lower austenitization temperatures, [220] however, when cooled from higher austenitization temperatures, non-equilibrium segregation dominates. [221] Though it is clear that B segregation to austenite grain boundaries delays ferrite nucleation, the mechanism leading to such a state is not clear yet. One proposed mechanism explains the delay of nucleation as follows.…”

Section: Effects Of Boron On Phase Transformationmentioning

confidence: 99%

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

Raabe

Sun

Silva

et al. 2020

Metall Mater Trans A

134

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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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“…The effect of the Cottrell atmosphere around boundaries may be responsible for this change. Carbon atoms segregate around boundaries and dislocations to reduce distortion energy, leading to the formation of the Cottrell atmosphere [36][37][38]. During the slipping process, the dislocations are forced to move along with the Cottrell atmospheres, resulting in the so-called "drag effect", which can effectively increase the resistance of the dislocation movement and pin the dislocation.…”

Section: Effect Of Carbon Content On the Effective Grain Size Of Strementioning

confidence: 99%

The Effect of Lath Martensite Microstructures on the Strength of Medium-Carbon Low-Alloy Steel

Sun

Liu

et al. 2020

Crystals

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Different austenitizing temperatures were used to obtain medium-carbon low-alloy (MCLA) martensitic steels with different lath martensite microstructures. The hierarchical microstructures of lath martensite were investigated by optical microscopy (OM), electron backscattering diffraction (EBSD), and transmission electron microscopy (TEM). The results show that with increasing the austenitizing temperature, the prior austenite grain size and block size increased, while the lath width decreased. Further, the yield strength and tensile strength increased due to the enhancement of the grain boundary strengthening. The fitting results reveal that only the relationship between lath width and strength followed the Hall–Petch formula of. Hence, we propose that lath width acts as the effective grain size (EGS) of strength in MCLA steel. In addition, the carbon content had a significant effect on the EGS of martensitic strength. In steels with lower carbon content, block size acted as the EGS, while, in steels with higher carbon content, the EGS changed to lath width. The effect of the Cottrell atmosphere around boundaries may be responsible for this change.

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Three-dimensional atom probe analysis of boron segregation at austenite grain boundary in a low carbon steel - Effects of boundary misorientation and quenching temperature

Cited by 59 publications

References 19 publications

Grain-boundary segregation of boron in high-strength steel studied by nano-SIMS and atom probe tomography

Grain-boundary segregation of boron in high-strength steel studied by nano-SIMS and atom probe tomography

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

The Effect of Lath Martensite Microstructures on the Strength of Medium-Carbon Low-Alloy Steel

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