記述言語：英語   出版者・発行元：Springer  

Combined addition of interstitial-substitutional elements has been acknowledged to contribute to the increase in the strengths of steels. For further improvements in mechanical properties, their atomic-scale interaction mechanisms with dislocations are required to be examined. In this study, both high-resolution transmission electron microscopy and atom-probe tomography were used to correlate interstitial-substitutional elements with dislocation characteristics in austenitic stainless steels. Three types of dislocation core structures are identified and associated with their strain fields as well as N and Cr atoms in the N-added steels. It is revealed that N atoms interact elastically with the dislocations, followed by the segregation of Cr atoms via the chemical interaction between N and Cr atoms. This insight significantly improves the understanding of the multiple alloying mechanism in metallic materials such as interstitial alloys and high-entropy alloys.

CiNii Research

記述言語：日本語   出版者・発行元：公益社団法人 日本金属学会  

DOI： 10.2320/materia.63.69

CiNii Research

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記述言語：英語   出版者・発行元：一般社団法人 日本鉄鋼協会  

<p>The structures of carbon clusters and carbides in a low-carbon ferritic steel were investigated at atomic-scale by annular dark-field scanning transmission electron microscopy. In the low-carbon ferritic steel aged at 473 K for 1 h, some homogeneously dispersed ε-carbides were formed within the matrix as closely spaced granules aligned to <001> of the ferrite matrix, and others were heterogeneously formed on AlN precipitates. The ε-carbides formed on AlN precipitates were coexisted with carbon clusters with c/a ratio of 1.1, possibly formed via Zener-ordering. In-situ heating experiments showed that ε-carbides acted as precursors for θ-carbides via dissolution of ε-carbides. The microstructural evidence showed that the precipitation sequence of the low-carbon ferritic steels aged at 473 K is proposed as: supersaturated solid-solution → carbon clusters → ε-carbides → θ-carbides, suggesting that Zener-ordering should be the most fundamental step for the carbide precipitation sequence.</p>

DOI： 10.2355/isijisss.2024.0_88

CiNii Research

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada  

DOI： 10.1093/micmic/ozad067.141

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PubMed

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Acta Materialia  

Carbon redistribution is one of the fundamental issues in quenched and aged carbon steels, which results in carbon clustering and carbide precipitation. Carbon clusters and carbides act as obstacles for dislocations, which have been known closely correlated with strengths of steels. In this study, conventional TEM, atomically-resolved TEM and In-situ heating TEM observations were carried out to understand carbon redistribution in a low-carbon ferritic steel aged at 473 K. Some ε-carbides were uniformly precipitated in the matrix, and the others were heterogeneously precipitated along dislocations. These ε-carbides were coexisted with carbon clusters with c/a ratio of 1.1, assumed to be the formation of Zener-ordered Fe8C. Moreover, θ-carbides were found precipitated from ε-carbides via dissolution of ε-carbides, confirmed by In-situ heating TEM experiments. These results suggested that Zener ordering should be the fundamental step for the following carbide precipitation sequences in the steel aged at 473 K.

DOI： 10.1016/j.actamat.2023.118919

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Materials Characterization  

Low-temperature aging treatment at 323 K results in the dramatical increase in hardness in low-carbon ferritic steels quenched from 983 K, possibly caused by carbon clusters and/or fine ε-carbides. In this study, transmission electron microscopy (TEM) analysis was carried out to characterize the change of the microstructure during the low-temperature aging treatment. Until the early stage of the peak hardness, the carbon clusters were formed homogeneously with zig-zag structures. At the latter stage of the peak hardness, it was found that the ε-carbides were partially precipitated within the carbon clusters, which suggested that the carbon clusters might have acted as the precursors of ε-carbides. In-situ tensile TEM observations showed that dislocation motions were free-glide type, and carbon clusters and fine-carbides interacted with dislocations via cutting-type. Dislocation interaction force was also evaluated, which suggested that the lattice misfit played as important role of the interaction mechanism.

DOI： 10.1016/j.matchar.2021.111579

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記述言語：その他   掲載種別：研究論文（学術雑誌）  

Microstructures of both as-quenched and intercritical-annealed medium-Mn steel were investigated by transmission electron microscopy to acquire a better understanding of γ–ɛ and γ–α′ martensitic transformations. The orientation relationships among each phases were determined as (1¯10)α′//(0001)ε,[111]α′//[112¯0]ε for the case of as-quenched sample, and (1¯10)α′//(1¯11)γ//(0001)ε,[111]α′//[110]γ//[112¯0]ε for the case of intercritical-annealed sample, respectively. In addition, the presences of core-shell type microstructures with the gradient of Mn concentration were confirmed with ɛ–martensite being surrounded by retained γ. Mn concentration of each phase was found dependent on the growth of reversed γ controlled by Mn diffusion during intercritical annealing. It was strongly suggested that the gradient of Mn concentration occurred during intercritical annealing affected the phase stability, which resulted in the formation of ε/γ core-shell microstructures.

DOI： 10.1016/j.scriptamat.2020.10.044

記述言語：その他   掲載種別：研究論文（学術雑誌）  

Austenitic stainless steels have superior room temperature and high temperature strengths, strongly influenced by stacking-faults in the steel microstructure. Nitrogen addition makes substantial contribution to room temperature and high temperature strengths, so it is essential to consider the effect of nitrogen on the stacking-fault energies (SFE) to understand strength mechanism of the steel and to enhance the strength. In this study, SFE were measured by weak-beam TEM method, and deformation mechanisms of nitrogen-added austenitic stainless steels at room temperature and at high temperature (1 173 K) were discussed in terms of SFE in Si-added austenitic stainless steel (Fe-19 wt&#37;Cr-13 wt&#37;Ni-0.05 wt&#37;C-3 wt&#37;Si-x wt&#37;N). Nitrogen addition resulted in the decrease of SFE, which changed dislocation structures at room temperature and at 1 173 K. At room temperature, nitrogen addition resulted in dislocation localization, and at 1 173 K, all samples formed the sub-grain structure, caused by the dislocation recovery. It was revealed that the increase of nitrogen content resulted in the increase of the dislocation density in the sub-boundary, which indicates that the decrease of SFE contributes to the high temperature strength.

DOI： 10.2355/ISIJINTERNATIONAL.ISIJINT-2020-609

記述言語：その他   掲載種別：研究論文（学術雑誌）  

A new characterization method is proposed to study intergranular precipitates of polycrystalline material in the planar manner. A dual beam focused ion beam (FIB) - scanning electron microscopy (SEM) was applied to fabricate thin FIB lamella with a grain boundary parallel to the lamella to investigate for transmission electron microscopy (TEM). Distributions, microstructures and compositions of intergranular precipitates of austenitic stainless steel were then examined by TEM, scanning transmission electron microscopy (STEM), and energy dispersive X-ray spectroscopy (EDS). This plan-view microstructural characterization methods would play important roles in the case of materials where the intergranular precipitates play key roles for their physical and chemical properties.

DOI： 10.1016/j.micron.2020.102927

記述言語：その他   掲載種別：研究論文（学術雑誌）  

The morphology and crystal structure of the carbon cluster in a low-temperature aged low-carbon ferritic steel were clarified by performing conventional and in-situ TEM, and atomically-resolved ADF-STEM observation. The carbon cluster grow parallel to <001> direction of the matrix, whose morphology was presumed to be either disk or plate. Lattice constant of the carbon cluster was measured by peak fitting of atomic columns observed by ADF-STEM. The result clarified that the structure of the carbon cluster was martensite-like body-centered tetragonal (bct) structure. This martensite-like bct structure suggested that the carbon cluster was supersaturated with carbon atoms occupying specific octahedral sites.

DOI： 10.1016/j.matchar.2019.110006

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Atomically resolved STEM and 3DAP analysis of the dislocation dragging mechanisms in nitrogen-added Fe-Cr-Ni austenitic stainless steels

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Dislocation analyses in Nitrogen-added Austenitic Stainless Steels

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Influence of Cu addition on the atomic structure of early-stage precipitates in 6XXX alloys

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Nucleation and Phase Development of Precipitates in age-hardenable Aluminium Alloys studied by 4DSTEM

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Influence of nitrogen addition on the temperature dependences of hardening mechanisms in austenitic stainless steels

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Influences of Cu addition on precipitation hardening mechanisms in Al-Mg-Si alloys

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J-GLOBAL

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