掲載種別：研究論文（学術雑誌）   出版者・発行元：Materials Today Communications  

The investigation of heterogeneous deformation mechanisms in materials is important for understanding fracture mechanisms. In this study, uniaxial tensile deformation of polycrystalline α-titanium was numerically reproduced by three-dimensional crystal plasticity finite element analysis, and the following were revealed for the first time: (i) plate-like high-strain regions form inside the specimen, which are typically observed as band-like high-strain regions (high-strain bands: HSBs) on the surface of and cross-sections in α-titanium specimen, and (ii) the formation of HSBs also affects the work-hardening rate near the yielding point. The reasons for the difference in the formation mechanism of HSBs between the surface and inside were also discussed. The results obtained showed that active slip systems that contribute to the formation of HSBs may differ between the surface and inside of specimen, and strain in HSBs on the specimen surface is higher than that inside. The distributions of HSBs at the surface of and inside the specimen are determined by distributions of resolved shear stress. These results are important for understanding the differences in the fracture mechanisms between the surface and interior of materials.

DOI： 10.1016/j.mtcomm.2024.109230

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Water Practice and Technology  

This study converted slag from the steelmaking industry into an Fe2O3-rich nanocomposite using solvothermal technique for photodegradation of pharmaceutical wastewater in an immobilized mode. The nanocomposite was characterized using XRF, SEM, EDX, TEM, FTIR, XRD, and UV–Vis spectrometer. The XRF analysis result reveals a significant increase in the weight percent of Fe2O3 and SiO2, with a decrease in CaO content. The SEM images revealed the spherical and heterogeneous nature of the nanocomposite in shape and structure, while the FTIR confirms the increase in the vibration band of Si–O–Si and Fe–O with a reduction in the wide stretch mode of Ca–O. The XRD result illustrated the crystalline peak of Fe2O3 with a nanoparticle crystal size of 15.17 nm. The slag nanocomposite was used for the photodegradation of paracetamol. The optimum operating parameters were obtained using response surface methodology at an R2 value of 0.99 and p-value, 0.05. The degradation efficiency obtained at the optimum value was 96.96%. The degradation efficiency of the fifth repeated cycle of the immobilized nanocomposite was 77.89%. The degradation mechanism revealed that OH• radical was the major species of the degradation process. This work showed that slag nanocomposite might be effectively used for pharmaceutical wastewater treatment.

DOI： 10.2166/wpt.2023.152

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記述言語：英語   出版者・発行元：公益社団法人 日本金属学会  

Early-stage dislocation structures inside dislocation channels of rapid-cooled and tensile-deformed aluminum single crystals were investigated by using the bright field imaging mode in a scanning transmission electron microscope (STEM-BF). Inside dislocation channels, arrays of the prismatic dislocation loops originated from dislocations of the primary slip system, i.e., (1 1 1)[1̄ 0 1], were mainly formed. Dislocations of the primary coplanar slip systems such as (1 1 1)[0 1 1̄] and (1 1 1)[1̄ 1 0] were activated owing to internal stresses caused by the primary dislocations pile-up inside the cleared channels. The activated primary coplanar dislocations left the dislocation loops elongating along the edge dislocation directions behind them. Inter-dislocation-loop interactions occur especially at the arrays of the prismatic dislocation loops originated from dislocations of the primary slip systems and produce “butterfly shape” dislocation loops. As the “butterfly shape” dislocation loops have “sessile” junctions, they should act as “obstacles” against the following multiplications and glides of the dislocations. When the interactions proceed, “tangled structures” would be formed around the arrays of the prismatic dislocation loops originated from dislocations of the primary slip system.

DOI： 10.2320/matertrans.mt-m2023032

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

Mg–Zn–Y alloys that contain an Mg-based long-period stacking ordered (LPSO) phase exhibit excellent mechanical properties because of the kink bands formed by plastic deformation. Such “kink-band strengthening” has attracted significant attention. Herein, we conducted deformation tests on directionally solidified single-phase LPSO Mg85Zn6Y9 alloys to investigate the kink-band strengthening mechanism. High-angular resolution electron backscatter diffraction was performed to detect misorientation between the matrices on either side of the kink bands. The misorientations corresponded to the magnitudes of the Frank vectors of the disclinations around the kink, and closely matched the estimations from geometric analysis, which supported the existence of disclinations. Moreover, the Frank vector of the kink bands increased after shear deformation, which indicates that shear deformation introduced new disclinations around the kinks. Scanning electron microscopy demonstrated that the kinks clearly obstructed basal ⟨a⟩ slip. Furthermore, scanning transmission electron microscopy of a sheared kink band revealed dislocation pile-ups on both sides of the kink/matrix interface, as well as the formation of secondary kinks that stabilized the structure against shear deformation (i.e., self-accommodation) and bend contours caused by elastic stress fields. The results suggest that disclinations behave as long-range obstacles to dislocation motion (e.g., by reducing the increase in kink-band self-energy or by the elastic stress field of disclinations). We believe that this study will play a key role in identifying the factors responsible for kink-band strengthening in LPSO-phase Mg alloys and in understanding the phenomena underlying the strengthening mechanism.

DOI： 10.1016/j.actamat.2023.118785

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Nuclear Science and Technology  

The Japan Atomic Energy Agency (JAEA) has been developing 9Cr-oxide dispersion strengthened (ODS) tempered martensitic steel (TMS) as a candidate material for use in the fuel cladding tubes of sodium-cooled fast reactors (SFRs). The creep property is essential for the fuel cladding tube of SFR; the reliable prediction of in-reactor creep-rupture strength is critical for implementing the 9Cr-ODS TMS cladding tube in the SFR. This study investigated the quantitative correlation between the creep properties of 9Cr-ODS TMS at 700°C and the dispersions of nanosized oxides by analyzing the creep data and the material’s nanostructure. The possibility of deriving a formula for estimating the in-reactor creep properties of 9Cr-ODS TMSs based on an analysis of the nanostructure of neutron-irradiated 9Cr-ODS TMSs was also discussed. The creep properties of 9Cr-ODS TMS at 700°C closely correlated with the dispersion of nanosized oxide particles. The correlation between creep-rupture lives and nanosized oxide particle dispersion in 9Cr-ODS TMS was determined using existing creep models. The elucidation of correlation between the stress exponent of secondary creep rate and the nanostructure is essential to enhance future modeling reliability and formulation.

DOI： 10.1080/00223131.2022.2096147

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Materials Science and Engineering: A  

In textured α-Ti, band-like high-strain regions at approximately 45° to the loading direction are commonly observed under tensile deformation. Herein, such high-strain regions were called high-strain bands (HSB), and the reasons for the formation mechanism of HSBs were investigated by a uniaxial tensile test and crystal plasticity finite element (CPFE) analyses. First, we conducted a uniaxial tensile test of commercially pure titanium (CP–Ti) with a TD-split texture, where aggregates of (0001) split and incline in the transverse direction, and changes in strain distributions with deformation were observed by digital image correlation. The strain distributions showed that HSBs of approximately 45° to the loading direction were formed from the initial stage of deformation. Second, a geometric model including crystal orientation information was constructed from the crystal orientation map of the CP-Ti specimen obtained by electron back-scattered diffraction, and the cause of the formation of HSBs was investigated by CPFE analysis. The stress–strain relationship and strain distributions obtained by CPFE analysis correlated well with those obtained experimentally, and the HSBs were successfully reproduced. Finally, CPFE analyses were conducted when the loading conditions, critical resolved shear stress (CRSS), or elastic constants were changed. These results show that the HSBs formed from the initial stage of deformation and the distributions formed by elastic deformation changed depending on the elastic anisotropy. However, the distribution of HSBs after plastic deformation was unchanged by elastic anisotropy. This may be because the directions of easy deformation by elastic and plastic deformation coincided. Elastic anisotropy did not affect the distributions of HSBs formed by plastic deformation, and elastic and plastic deformations were predominantly determined by elastic constants and CRSS, respectively. Curved HSBs were also observed when plastic deformation-resistant regions occupied a large area in the specimen. In this case, the distributions of HSBs, caused by elastic deformation did not coincide with those of the plastic deformation.

DOI： 10.1016/j.msea.2023.144670

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Nature  

Abstract

Interstitial oxygen embrittles titanium, particularly at cryogenic temperatures, which necessitates a stringent control of oxygen content in fabricating titanium and its alloys. Here, we propose a structural strategy, via grain refinement, to alleviate this problem. Compared to a coarse-grained counterpart that is extremely brittle at 77 K, the uniform elongation of an ultrafine-grained (UFG) microstructure (grain size ~ 2.0 µm) in Ti-0.3wt.%O is successfully increased by an order of magnitude, maintaining an ultrahigh yield strength inherent to the UFG microstructure. This unique strength-ductility synergy in UFG Ti-0.3wt.%O is achieved via the combined effects of diluted grain boundary segregation of oxygen that helps to improve the grain boundary cohesive energy and enhanced <c + a> dislocation activities that contribute to the excellent strain hardening ability. The present strategy will not only boost the potential applications of high strength Ti-O alloys at low temperatures, but can also be applied to other alloy systems, where interstitial solution hardening results into an undesirable loss of ductility.

DOI： 10.1038/s41467-023-36030-0

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その他リンク： https://www.nature.com/articles/s41467-023-36030-0

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.62.14

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

In this study, pure titanium equivalent to Grade 1 was subjected to tensile tests at strain rates ranging from 10−6 to 100 s−1 to investigate the relationship between its mechanical properties and its twinning and slip. Deformation properties and microstructures of samples having average grain sizes of 210 μm (Ti-210), 30 μm (Ti-30), and 5 μm (Ti-5) were evaluated. With increasing strain rates, the 0.2% proof stress and ultimate tensile strength increased for all samples; the fracture strain increased for Ti-210, decreased for Ti-5, and changed negligibly for Ti-30. Comparing high (100 s−1) and low (10−6 s−1) strain rates, twinning occurred more frequently in Ti-30 and Ti-210 at high strain rates, but the frequency did not change in Ti-5. The frequency of 1st order pyramidal slip tended to be higher in Ti-30 and Ti-5 at low strain rates. The higher ductility exhibited by Ti-210 at high strain rates was attributed to the high frequency of twinning. In contrast, the higher ductility of Ti-5 at low strain rates was attributed to the activity of the 1st order pyramidal slip.

DOI： 10.3390/ma16020529

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

Systematic experiments were performed to determine where and when dislocations are induced during the thermal cycling of Ti–Ni shape memory alloys. The decrease in transformation temperatures upon thermal cycling became less pronounced with increasing Ni concentration, which was supported by the dislocation densities estimated from scanning transmission electron microscopy observations. The arrangement of transformation-induced dislocations after the 1st thermal cycle reproduced the self-accommodation structure of B19ʹ martensite. Three-dimensional visualization revealed that the complex spiral appearance of the dislocations after the 1st thermal cycle was attributable to the duplicated projection of relatively simple elongated dislocation loops aligned in the depth direction parallel to 〈111〉B2 along {110}B2. No dislocations were observed along the twin boundary in the initially transformed martensite, whereas there were numerous dislocations parallel to the trace of the {110}B2 planes in the martensite formed upon the 2nd thermal cycle. The results suggest that the transformation-induced dislocation loops were generated during the reverse transformation rather than the forward transformation. The possible source site of the transformation-induced dislocations is also discussed.

DOI： 10.1016/j.actamat.2022.118588

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担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 日本鉄鋼協会  

Oxide Dispersion Strengthened (ODS) ferritic steel, a candidate material for fast reactor fuel cladding, has low thermal expansion, good thermal conductivity, and excellent resistance to irradiation damage and high temperature strength. The origin of the excellent high-temperature strength lies in the dispersion of fine oxides. In this study, creep tests at 700°C or 750°C, which are close to the operating temperatures of fast reactors, and high-temperature tensile tests at 900°C to 1350°C, which simulate accident conditions, were conducted on 9Cr ODS ferritic steels, M11 and MP23, and 12Cr ODS ferritic steel, F14, to confirm the growth behavior of oxides. In the M11 and F14 creep test samples, there was little oxide growth or decrease in number density from the initial state, indicating that dispersion strengthening by oxides was effective during deformation. After creep deformation of F14, the development of dislocation substructures such as dislocation walls and subgrain boundaries was hardly observed, and mobile dislocations were homogeneously distributed in the grains. The dislocation density increased with increasing stress during the creep test. In the high-temperature ring tensile tests of MP23 and F14, the strength of both steels decreased at higher temperatures. In MP23, elongation decreased with increasing test temperature from 900°C to 1100°C, but increased at 1200°C, decreased drastically at 1250°C, and increased again at 1300°C. In F14, elongation decreased with increasing temperature. It was inferred that the formation of the δ-ferrite phase was responsible for this complex change in mechanical properties of MP23 from 1200 to 1300°C.

DOI： 10.2355/tetsutohagane.tetsu-2022-080

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 日本鉄鋼協会  

The creep deformation behavior and microstructure of a N-containing steel expected to exhibit high creep strength and excellent oxidation resistance were investigated. Even for steel with a high W content, it was possible to form a martensitic microstructure by adding a sufficient amount of N. Comparison of the microstructures of the N-containing steel and a C-containing steel confirmed that the two steels have the same crystal orientation relationship. The N-containing steel precipitated with the Laves phase as a strengthening phase displayed a higher creep strength than conventional steel under relatively high stress. However, the superiority of the creep strength of the N-containing steel relative to the conventional steel decreased under low stress. The stress exponent of the N-containing steel was different from those of the C-containing steel and the conventional steel. This deference considered to be ascribed to the difference of variation behavior of dislocation density during creep deformation.

DOI： 10.2355/tetsutohagane.tetsu-2022-065

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記述言語：日本語   出版者・発行元：一般社団法人 日本鉄鋼協会  

DOI： 10.2355/tetsutohagane.109.149

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出版者・発行元：28th IFHTSE 2023 Congress  

Lath martensitic steel is expected to be applied to automobile body structures. It is necessary to balance the strength and ductility to clarify the relation between microstructural factors and mechanical properties. Manganese is known to increase the work-hardening rate of lath martensitic steels. However, the reason for this has not been clarified yet. In this study, low-carbon lath martensitic steels with different manganese concentrations were observed by microscopy, served tensile tests, and strain distribution observations by the microscale digital image correlation analysis. The work-hardening rate of martensitic steel containing 8 mass% manganese was higher than that of martensitic steels containing 3 and 5 mass% manganese. When the macroscopic nominal strain was 0.01, in-lath slips were activated in martensitic steel containing 5 mass% manganese. On the other hand, out-of-lath slips as well as the in-lath slips were activated in martensitic steel containing 8 mass% manganese. Twins, called long twins, whose longitudes are the same as the longitude of laths exist in both martensitic steels containing 5 and 8 mass% manganese. Short twins that partially cross the lath were only observed in martensitic steel containing 8 mass% manganese. Because twin boundaries are high-angle boundaries, the short twins are supposed to prevent the development of in-lath slip deformation and promote out-of-lath slip deformation. This seems to be the mechanism of the higher work-hardening behavior observed in martensitic steel containing 8 mass% manganese.

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出版者・発行元：Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals  

Early–stage dislocation structures inside dislocation channels of rapid–cooled and tensile–deformed aluminum single crystals were investigated by using the bright field imaging mode in a scanning transmission electron microscope (STEM–BF). Inside dislocation channels, arrays of the prismatic dislocation loops originated from dislocations of the primary slip system, i.e., ð1 1 1Þ½1- 0 1], were mainly formed. Dislocations of the primary coplanar slip systems such as ð1 1 1Þ½0 1 1-] and ð1 1 1Þ½1- 1 0] were activated owing to internal stresses caused by the primary dislocations pile–up inside the cleared channels. The activated primary coplanar dislocations left the dislocation loops elongating along the edge dislocation directions behind them. Inter–dislocation–loop interactions occur especially at the arrays of the prismatic dislocation loops originated from dislocations of the primary slip systems and produce “butterfly shape” dislocation loops. As the “butterfly shape” dislocation loops have “sessile” junctions, they should act as “obstacles” against the following multiplications and glides of the dislocations. When the interactions proceed, “tangled structures” would be formed around the arrays of the prismatic dislocation loops originated from dislocations of the primary slip system.

DOI： 10.2320/jinstmet.J2022030

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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 Science and Engineering: A  

In this study, the criteria for {112‾2} compression twinning in commercially pure titanium (CP–Ti) were investigated by uniaxial tensile tests, crystal plasticity finite element (CPFE) analyses, and slip operation factor (SOF) calculations. First, the aggregates of the [0001] axes of CP-Ti were inclined in the rolling direction (RD), implying its RD-split texture. The development of the crystal orientation distribution with deformation was observed by electron back-scattered diffraction (EBSD). Active slip systems were identified by kernel average misorientation (KAM) and intergranular misorientation axis (IGMA) analyses. The dominant slip system was prismatic <a>, whereas the non-prismatic <a> slip systems were activated near the grain boundary. Active twin systems were also identified by the rotation angles of the [0001] axes between the twin and matrix. The dominant active twin system was the {112‾2} compression twin, although a uniaxial tensile load was applied. Second, the positions of {112‾2} twinning were predicted by CPFE analysis using the resolved shear stress (RSS) criterion while considering plastic deformation. SOF analysis was also employed for the prediction. The CPFE and SOF analyses yielded almost the same level of prediction accuracy. However, these calculations do not completely predict the twinning positions. Finally, the criteria for {112‾2} twinning were discussed, and it was revealed that hydrostatic pressure and RSS are possible criteria for {112‾2} twinning in the continuum model.

DOI： 10.1016/j.msea.2022.143302

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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：ISIJ International  

The effects of the neodymium content on the creep properties and microstructures of 9Cr-3Co-3W-Nd-B steel were investigated. Neodymium had a mild effect on the creep rupture strength at contents up to 0.056 mass%. This suggested that the effects of neodymium compounds and solid-dissolved neodymium were minimal in the microstructures and uniformly creep-deformed parts after normalizing and tempering heat treatment. On the other hand, the reduction of area after creep rupture was improved by the addition of neodymium. Creep rupture occurred at the prior austenite grain boundaries on steel without neodymium. Therefore, neodymium conclusively adhered to the segregated sulfur at the prior austenite grain boundaries to suppress the formation of creep cracks.

DOI： 10.2355/isijinternational.isijint-2022-057

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記述言語：日本語   出版者・発行元：一般社団法人 軽金属学会  

The mechanical properties of JISAC8A alloys (Al-12%Si-1%Mg-1%Ni-1%Cu alloy) fabricated by laser-based powder bed fusion (LB) or electron-based powder bed fusion (EB) or gravity casting (CAST) were studied by means of tensile tests at room temperature and 300°C. These alloys were under two types of heat-treatment sequences. One was a T6 treatment, which was corresponding to the heat treatment at 500°C for 2h and 170°C for 4 h, followed by the annealing at 300°C for 10 h. Another was directly annealed at 300°C for 10 h after the fabrication. In the annealed specimens without T6 treatment, the LB alloy showed the highest strength and best elongation at room temperature and 300°C, because eutectic Si particles and Al-Ni-Cu-Fe compounds formed very fine network structure in Al matrix. In the annealed specimens with T6 treatment, the tensile strength at room temperature did not depend on the fabrication methods but the LB alloy showed the best elongation because of finer and isotropic shape of secondary phase particles. The annealed CAST alloy showed the highest strength at 300°C, and the annealed LB alloy showed the lowest strength at 300°C.

DOI： 10.2464/jilm.72.206

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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 Science and Engineering: A  

It is possible that strain localization in polycrystalline α-Ti leads to the fracture, and it is crucial to evaluate the local slip activities for individual slip systems depending on their textures and loading conditions. In this study, the effects of textures and strain rates on local slip activities were investigated using the crystal plasticity finite element method. For the analysis, microstructural models of α-Ti with the following three textures were employed: aggregates of (0001) axes are (i) splitting in rolling direction (RD-split texture), (ii) splitting in transverse direction (TD-split texture), and (iii) aligned in normal direction (basal texture). For each texture model, two variations in the crystal orientation distributions were considered, namely, small and large scatterings of crystal orientations in the (0001) axes by normal random numbers. The differences in the strain rate sensitivities of the critical resolved shear stresses (CRSSs) among slip systems were also considered. Tensile loading was applied by a forced displacement in the RD with two strain rate conditions of 1.0 × 10−4 s−1 and 1.0 × 10−1 s−1. Local non-prismatic slips were easier to operate in the models with basal and RD-split textures than with the TD-split texture. The slip strains for non-prismatic slip systems were higher at higher strain rates, while activities in the prismatic slips decreased with an increase in strain rates. The mechanism of the exchange of slip system activities can be explained by strain redistribution between hard and soft regions and changes in CRSS as a function of strain rates.

DOI： 10.1016/j.msea.2022.143133

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記述言語：日本語  

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本金属学会  

Tangled dislocation structures inside the dislocation channels of rapid-cooled and tensile deformed aluminum single crystals were investigated by using BF-STEM. Inside the dislocation channels, arrays of the prismatic dislocation loops belonging to the primary slip system, i.e., (1 1 1)[1 0 1], were mainly formed. Dislocations of the primary coplanar slip systems such as (1 1 1)[0 1 1] and (1 1 1)[1 1 0] were activated due to the internal stresses caused by the primary dislocations pile-up inside the cleared channels. The activated primary coplanar dislocations leave the dislocation loops elongated along the edge dislocation directions behind them. Inter-dislocation-loop interactions take place especially at the arrays of the prismatic dislocation loops of the primary slip systems and produce “butterfly shape” dislocation loops. Since the “butterfly shape” dislocation loops have “sessile” junctions, they should act as “obstacles” against the following multiplications and glides of the dislocations. As the interactions proceed, the arrays are stabilized and grow as “tangles”.

DOI： 10.2320/matertrans.mt-m2021230

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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 Science and Engineering: A  

To clarify the effect of twinning deformation on the work-hardening behavior of commercially pure titanium, the changes in the grain size and texture due to twinning deformation were investigated, along with the grain-size dependence of the work-hardening behavior. In specimens with an average grain size of 10 μm or less, twinning deformation was inactive, and the instantaneous work-hardening exponent (n = d(lnσ)/d (lnε)) was constant at approximately 0.2. For specimens in which twinning deformation occurred, the average grain size decreased and the texture changed with increasing strain due to twinning deformation, which resulted in an increase in the instantaneous n value. In the grain-size range at which twinning deformation did not occur, the smaller the grain size, the higher the rate of increase in the dislocation density and the greater the activity of ⟨c + a⟩-type dislocations, resulting in an increased strain hardening rate. Furthermore, the flow stress could be approximated using only the Bailey–Hirsh equation. The promotion of work hardening by twinning deformation can be mostly explained by the increase in the dislocation density increment rate, increase in the fraction of ⟨c + a⟩ dislocation due to grain refinement, and change in the Taylor factor due to the change in the texture.

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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.61.84

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その他リンク： https://www.jstage.jst.go.jp/article/materia/61/2/61_84/_pdf

記述言語：日本語   出版者・発行元：九州大学大学院総合理工学府  

Active twinning systems during compression deformation at temperatures from 25°C to 700°C were investigated using SEM/EBSD techniques in order to clarify the effects of oxygen and aluminum addition on twinning deformation in titanium. Four twinning systems have been confirmed in commercially pure titanium, Ti-0.2mass%O and Ti-2mass%Al under compression at 10% strain. The addition of oxygen suppresses the activity of all the twin systems at 25°C, but only slightly above 200°C. On the other hand, the addition of aluminum suppressed the activity of only the {112̅2} twin. It is supposed that the suppressive effect of the oxygen addition is mediated by thermal activation processes such as diffusion and lattice vibration, while that of the aluminum addition is brought about by the suppression of <c^+a> slip.

DOI： 10.15017/4763153

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記述言語：日本語   出版者・発行元：一般社団法人 日本鉄鋼協会  

The effects of the neodymium content on the creep properties and metallographic structure of 9Cr-3Co-3W-Nd-B steel were investigated. Neodymium had a mild effect on the creep rupture strength at contents up to 0.056 mass%. This suggested that the effects of neodymium compounds and solid-dissolved neodymium were minimal in the microstructures and uniformly creep-deformed parts after normalizing and tempering heat treatment. On the other hand, the reduction of area after creep rupture was improved by the addition of neodymium. Creep rupture occurred at the prior austenite grain boundaries on steel without neodymium. Therefore, neodymium conclusively adhered to the segregated sulfur at the prior austenite grain boundaries to suppress the formation of creep cracks.

DOI： 10.2355/tetsutohagane.tetsu-2021-103

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.jallcom.2021.161154

記述言語：その他   掲載種別：研究論文（学術雑誌）  

Scanning transmission electron microscopy (STEM) is suitable for visualizing the inside of a relatively thick specimen than the conventional transmission electron microscopy, whose resolution is limited by the chromatic aberration of image forming lenses, and thus, the STEM mode has been employed frequently for computed electron tomography based three-dimensional (3D) structural characterization and combined with analytical methods such as annular dark field imaging or spectroscopies. However, the image quality of STEM is severely suffered by noise or artifacts especially when rapid imaging, in the order of millisecond per frame or faster, is pursued. Here we demonstrate a deep-learning-assisted rapid STEM tomography, which visualizes 3D dislocation arrangement only within five-second acquisition of all the tilt-series images even in a 300 nm thick steel specimen. The developed method offers a new platform for various in situ or operando 3D microanalyses in which dealing with relatively thick specimens or covering media like liquid cells are required.

DOI： 10.1038/s41598-021-99914-5

記述言語：日本語  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Time evolution of precipitates related to age-hardening in Ti–2.3 wt pct Cu alloys was investigated by electron microscopy. In isothermal aging at 723 K, the hardness increases continuously owing to precipitation strengthening, whereas in two-step aging where the aging temperature is switched from 673 K to 873 K after 100 hours, the hardness is found to drastically drop after the aging temperature switches. In isothermal aging, metastable and stable precipitates are independently nucleated, whereas characteristic V-shaped clusters of precipitates are observed during the two-step aging. It is revealed by atomic-scale observations that the V-shaped clusters are composed of metastable and stable precipitates and each type of precipitate has a different orientation relationship with the α phase: (10 3 ¯) //(0001) and [0 1 ¯ 0] //[11 2 ¯ 0] for the metastable, and (201)//(1 1 ¯ 03) and [0 1 ¯ 0] //[11 2 ¯ 0] for the stable precipitates, respectively. The drop in hardness during two-step aging can be explained by a synergistic effect of decreased precipitation strengthening and solid solution strengthening. α α α α

DOI： 10.1007/s11661-021-06265-x

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A 3-μm-thick film of Magnéli Ti O was successfully fabricated on the surface of Ti metal foil by a stepwise oxidation process involving annealing at 973 K in air followed by heating to 1173 K under a low oxygen partial pressure. Transmission electron microscopy and high-angle annular dark-field scanning transmission electron microscopy showed that the Magnéli Ti O phase consisted of a period of four layers of equiaxial grains several hundreds of nanometers in size. The black Magnéli Ti O thin film formed by our process absorbed light in the visible and near-infrared regions. 4 7 4 7 4 7

DOI： 10.1016/j.scriptamat.2021.113829

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A quantitative evaluation method of a serration deformation behavior by a dead-weight tensile test combined with a strain measurement by a DIC method is proposed. This method applies to binary solid solution aluminum alloys and a ternary cluster strengthened aluminum alloy. In the dead-weight tensile test, the serrated flow was measured as a stress-strain curve with a stepped-shape divided into two stages of a stress rising phase and a strain burst phase. By adopting this tensile test, the serration deformation behavior can be measured with an extremely reproducibility. It was confirmed that an elastic deformation occurs predominantly in the stress rising phase, and this deformation behavior is discussed in relation to the concentration of solid solution elements. Propagation of PLC bands has occurred in the strain burst phase. An activation volume obtained from the strain rate in the PLC bands was in good agreement with a calculated value based on a distribution interval assuming a regular square distribution of solute elements. For the ternary alloy strengthened by clusters, it is also shown that this method can be applied to the qualitative estimation of the change in the residual amount of the solid solution element in the matrix during natural aging.

DOI： 10.1016/j.msea.2021.141277

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/jmicro/dfaa060

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.triboint.2020.106781

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Thermoelastic martensitic transformation (MT) plays a vital role in shape memory effects and superelasticity of various alloys. To understand the self-accommodation mechanism of the MT of Zr–Co–Pd alloys, which demonstrate typical MT from B2 to B33 structure, the configuration of the alloy’s martensite variants and their crystallographic relationship were investigated by electron backscatter diffraction, transmission electron microscopy, and high-angle annular dark-field scanning transmission electron microscopy. Results suggest that two habit plane variants (HPVs) bounded by {021} compound twinning are formed around each < 100> axes of the B2 parent phase. It is determined that the minimum self-accommodation unit, to relax the strain energy accompanying MT, is a pair of trapezoid- or triangle-shaped HPVs. No lattice invariant shear exists in the martensite variants with a trapezoid- or triangle-shape. In the latter stage of MT, each HPV pair may contact and impinge on {110} plane of B2 parent phase, which is shear and shuffling plane on MT. The combination of the four variants forms the roof-type morphology. B33 B2 B2

DOI： 10.1007/s10853-020-05599-y

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.mtcomm.2021.102041

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/matertrans.MT-M2020255

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2355/isijinternational.ISIJINT-2020-315

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2464/JILM.70.405

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.cossms.2020.100850

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.mtla.2020.100716

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.actamat.2020.04.051

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2355/isijinternational.ISIJINT-2019-707

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Uniaxial tension experiments and electron backscatter diffraction were performed on a bimodal Ti-6Al-4V alloy to study in situ the deformation behavior of primary hcp-Ti (α_p). It was found that the strain could be accommodated by the activation of slip systems and by grain rotations. The prismatic slip was the primary slip mode of the α_p. From the analysis of kernel average misorientation and geometrically necessary dislocation, it was shown that the dislocations mainly distributed in the vicinity of grain and sub-grain boundaries, and part of the dislocations distributed around slip lines. It was the dislocation activities that led to the formation of the low angle grain boundary and its transformation to the high angle grain boundary. It's important that tracking of deformation heterogeneities with significance to performance. By analyzing the rotation angle, average rotation rate, and rotation path of grains, it was shown that grain rotation heterogeneity occurred during the deformation. From the observation of the loading direction, grain rotation paths kept with the texture evolution direction of all α_p. The grains activated in the basal slip gradually rotated to the ⟨101¯1⟩ pole and enhanced the intensity of the ⟨101¯1⟩ texture. Meanwhile, the grains activated in prismatic or 1st-order pyramidal slip rotated to the ⟨101¯0⟩ pole and enhanced the intensity of the ⟨101¯0⟩ texture. Grain rotation and texture evolution are related to mechanical properties.

DOI： 10.1016/j.matchar.2020.110282

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/jmicro/dfaa002

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2355/tetsutohagane.TETSU-2019-082

記述言語：英語   掲載種別：研究論文（学術雑誌）  

An indicator to predict the slip operation at the crystal-grain level, namely slip operation factor (SOF), was established as a function of the Schmid factor (SF) and critical resolved shear stress (CRSS). Plastically "soft" and "hard" regions were estimated by the Schmid factor values normalized by the CRSS - the normalized Schmid factor (NSF). The effect of the interaction among the regions was incorporated into SOF. A microstructural map of α-titanium (α-Ti) was obtained by the electron backscatter diffraction patterns. Several spatial distributions of SOF were calculated based on the map by changing the interaction range among the regions. The distributions were compared with those of the strains obtained by the crystal plasticity finite element (CPFE) analysis. Good agreement between the distributions was found near the macroscopic yield point when the interaction range was appropriate, although some significant differences between the distributions were also noticed after the yielding point. The prediction accuracy by SOF was higher than that by SF and NSF. The reasons for the high accuracy revealed by the SOF analysis and the differences between the distributions indicated by the CPFE analysis were also investigated.

DOI： 10.1016/j.ijplas.2019.12.001

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/matertrans.MT-MJ2019002

記述言語：日本語  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/met9040468

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2355/tetsutohagane.TETSU-2018-043

記述言語：日本語  

DOI： 10.2320/materia.58.90

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Inhomogeneous deformation of a single ¡-¢ colony in a Ti6Al4V alloy under uniaxial tensile conditions was numerically simulated using a crystal plasticity finite element (CPFE) method, and we predicted density changes in geometrically necessary dislocations (GNDs) depending on the vanadium concentration in the ¢ phase (V_¢). The geometric model for the CPFE analysis was obtained by converting data from electron back-scatter diffraction patterns into data for the geometric model for CPFE analysis, using a data conversion procedure previously developed by the authors. The results of the image-based crystal plasticity analysis indicated that smaller V_¢ induced greater stress in the ¡ phase and smaller stress in the ¢ phase close to the ¡-¢ interfaces in the initial stages of deformation because of the elastically softer ¢ phase with lower V_¢. This resulted in greater strain gradients and greater GND density close to the interfaces in the initial stages of deformation within the single ¡-¢ colony when the ¢ phase plastically does not deform.

DOI： 10.2320/matertrans.M2019016

記述言語：日本語  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1080/14786435.2018.1524161

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1088/1361-6641/aae4bd

記述言語：日本語  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acsnano.8b03055

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/matertrans.M2018146

記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

DOI： 10.1299/jsmemm.2018.OS1420

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1149/2.0421712jss

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2355/isijinternational.ISIJINT-2017-758

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/jinstmet.J2017025

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2355/tetsutohagane.TETSU-2016-107

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.matchar.2017.04.010

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2355/isijinternational.ISIJINT-2016-712

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/matertrans.M2016407

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1109/TED.2016.2639363

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2355/tetsutohagane.TETSU-2016-057

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/matertrans.M2016291

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1088/1361-6528/28/2/025704

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/matertrans.M2017035

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/jinstmet.J2016069

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.actamat.2016.09.006

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.7567/APEX.9.065502

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.15282/jmes.10.1.2016.14.0182

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s11661-016-3344-7

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/matertrans.MB201505

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1080/09500839.2016.1154200

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.actamat.2015.10.017

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.4930573

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.scriptamat.2015.02.001

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1080/14786435.2015.1021400

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1080/09500839.2014.995739

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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：Journal of Tribology  

A series of coarse-grained molecular dynamics simulations were conducted to investigate the temporal evolution of frictional behaviors of lubricants between sliding nanostructured iron surfaces. Grain boundary atoms were given a stronger interaction with the lubricant molecules. We varied the surface distance and interaction strength between grain boundary atoms and lubricants. It was found that, below the critical compressive stress, the oil film detached from the surface at first and then attached to it after several nanoseconds due to the localized molecular rearrangement within lubricants and the enhancement of interaction between lubricants and iron surfaces. The transition times required for oil film formation and de-lamination both increased as it approached the critical compressive stress. Larger interaction strength increased the delamination time but barely affected the formation time.

DOI： 10.1115/1.4064860

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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：Journal of Alloys and Compounds  

The addition of Mn in Al–Fe alloys stabilizes the Al6Fe metastable phase (orthorhombic structure, oC28) owing to the partial occupation of Fe sublattice sites by Mn atoms (formation of Al6(Fe, Mn) phase), thereby achieving superior high-temperature strength of Al–Fe–Mn ternary alloys that are manufactured via laser powder bed fusion (L-PBF) process. This study aimed to fundamentally understand the thermal stability of the refined Al6(Fe, Mn) phase formed in the L-PBF fabricated Al–2.5%Fe–2%Mn alloy in terms of a thermodynamic approach and the kinetics of morphological changes in the Al6(Fe, Mn) phase at elevated temperatures ranging from 200 to 500 ℃. The L-PBF processed samples showed a high hardness of approximately 125 HV due to the formation of numerous dispersoids of the Al6(Fe, Mn) phase with sizes of several tens of nanometers in the α-Al matrix containing concentrated solute elements of Fe and Mn. The hardness and microstructure were almost unchanged even after exposure to a high temperature of 200 ℃ for an extended period of 1000 h. Upon exposure to 300 ℃, nucleation and growth of the Al6(Fe, Mn) phase occurred locally, particularly at grain boundaries in the α-Al matrix. Such a local growth contributed to a reduction in hardness upon thermal exposure. Simultaneously, numerous nanoscale precipitates were formed in the α-Al matrix, resulting in a suppressed reduction in hardness. Contrary to the result of the thermodynamic calculations, the θ-Al13Fe4 phase was scarcely found even after long-term exposure to 500 ℃. The θ-phase formation was accompanied by the dissolution of the refined Al6Fe metastable phase for strengthening, which significantly reduced the hardness during thermal exposure. The suppressed θ-phase formation could be associated with the thermodynamically stable Al6(Fe, Mn) phase developed during the L-PBF process, which predominantly contributed to the high microstructural stability of the L-PBF fabricated Al–Fe–Mn alloy at elevated temperatures.

DOI： 10.1016/j.jallcom.2024.174593

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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 Science and Engineering: A  

Plastic anisotropy in the yield stress of pearlitic steels evolved by drawing was studied. The tension and compression tests were performed in parallel and perpendicular directions to the drawing direction. The yield stress in the parallel tension and vertical compression tests increased with the increase in drawing strain. On the other hand, in the parallel compression, the yield stress decreased significantly at the small drawing strain and then increased at the larger strain. The difference between the yield stress at the tension and at the compression did not change largely after the start of the drawing. The observation of microstructure indicated no significant heterogeneity of the deformation microstructure and texture at the different locations in the radial direction of the drawn samples, meaning that the plastic anisotropy was brought by reasons other than the non-uniformity of the deformation condition. The measurement of the distribution of the local misorientation in ferrite suggested the large plastic deformation even at smaller strain by drawing. This result indicates that the residual stress in plastically deformed ferrite brings back stress, which can be the source of the plastic anisotropy.

DOI： 10.1016/j.msea.2024.146380

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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：一般社団法人 日本鉄鋼協会  

Microstructures of lath martensite have been studied intensively to understand their effect on the mechanical properties of steels. It is, however, said that the relation between microstructural factors and mechanical properties has not been clarified yet. The plastic deformation behavior of fully lath martensitic steels has become important because they are applied to automobile body structures such as bumper reinforcement. It is, therefore, important to understand the microstructural factors that control the work-hardening behavior of fully martensitic steels. Although we could not clarify differences in microstructural factors when manganese (Mn) concentrations of steels are altered, the work-hardening of 8 mass%Mn martensitic steel is much higher than that of 5 mass%Mn martensitic steel. It was found using the digital image correlation (DIC) method, that the strain concentration due to the in-lath-plane slip deformation is more developed in 5 mass%Mn martensitic steel than 8 mass%Mn martensitic steel. Transmission electron microscope (TEM) observations revealed the existence of two types of fine twins inside laths. Long twins that are parallel to the longitude of the lath are observed both in 5 mass%Mn and 8 mass%Mn martensitic steels. Short twins that partially cross the laths, on the other hand, can only be found in 8 mass%Mn martensitic steel. Since twin boundaries are high angle boundaries, the short twins are supposed to prevent the development of in-lath-plane slip deformation. This seems to be the mechanism of higher work-hardening behavior observed in 8 mass%Mn martensitic steel.

DOI： 10.2355/tetsutohagane.tetsu-2023-068

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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：Scripta Materialia  

Ferromagnetism can be induced by introducing oxygen vacancies into metallic oxides. The oxygen deficiencies introduced into ZrO2 samples thus far have been present in unquantifiable concentrations and randomly scattered near the surface. We successfully produced room-temperature-ferromagnetic 9 μm-thick ZrO2−x films via a stepwise oxidation process consisting of annealing metallic Zr foil in air and under a controlled oxygen partial pressure. The ZrO2−x films are composed of a periodic structure with a spacing of 3–4 nm; this structure originated from the presence and absence of oxygen deficiencies. The unique structure in the ZrO2−x phase consisting of the periodic arrangements of oxygen deficiencies can be produced by the stepwise oxidation using Zr metal. Our proposed process should open the door for new applications of defect-driven ferromagnetic films of undoped magnetic oxides with a periodic oxygen-defective structure.

DOI： 10.1016/j.scriptamat.2023.115944

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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：Journal of Nuclear Materials  

This paper discusses the applicability of Straalsund et al.’s technique for combining the Larson–Miller parameter (LMP) and life-fraction rule to form a single high-temperature strength equation for 9Cr-oxide-dispersion-strengthened (ODS) tempered martensitic steels (TMS). It uses the extensive dataset on creep rupture, tensile, and temperature-transient-to-burst tests of 9Cr-ODS TMS cladding tubes in the α-phase, α/γ-duplex, γ-phase matrices, which are accumulated by the Japan Atomic Energy Agency so far. The technique is adequately applicable to 9Cr-ODS TMS cladding tubes. A single high-temperature strength equation expressing the mechanical strength in different deformation and rupture modes (creep, tensile, temperature-transient-to-burst) is derived for 9Cr-ODS TMS cladding tubes. This equation can predict the rupture life of the cladding tubes under various stresses and temperatures over time. The applicable range of the high-temperature strength equation is specified in this study and the upper limit temperature for the equation is found to be 1200 °C. At temperatures higher than 1200 °C, the coarsening and aggregation of nanosized oxide particles and the γ to δ phase transformation are reported in previous studies. The high-temperature strength equation can be well applied to the creep and tensile strength in the α-phase matrix, the creep strength in the γ-phase matrix and the temperature-transient-to-burst strength in both phases except for the low equivalent stress (43 MPa) at temperatures exceeding 1050 °C. The mechanism of the notable consistency between creep and tensile strength in the α-phase matrix is discussed by analyzing the high-temperature deformation data in the light of existing deformation models. The study suggested the thermal activation process is dominant even for the high-temperature deformation modes exceeding yield stress in the 9Cr-ODS TMS with the fine-grained matrix.

DOI： 10.1016/j.jnucmat.2024.155008

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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：Environmental Nanotechnology, Monitoring and Management  

Electrical Furnace Steel slag (EAF) was converted into steel slag nanocomposite (SSNC) by solvothermal preparation technique and assisted by H2O2 for Fenton and photo-Fenton-like degradation of six different dyes in both suspension and spin-coated modes. The physico-chemical properties were evaluated using various characterization tools. The result reveals that the EAF-SSNC exhibited nanocomposite behaviour. As a substrate for studying the advance oxidataion processes, methylene blue (MB) was first used. The kinetic study followed the pseudo-first-order reaction kinetics. The effect of operating factors was studied using the response surface methodology. Based on the optimum parameters, five reusability test was performed for both suspension and spin-coated mode, where 92.89% of MB was degraded in the fifth cycle for suspension mode and 88.21% for spin-coated mode. The photodegradation efficiency of methylene blue, methyl red, rhodamine-B, Congo red, acid blue-25, and methyl orange were 85.84%, 74.62%, 70.53%, 58.66%, 45.21%, and 40.38%, respectively, at a neutral pH. The effect of scavenger and total organic carbon (TOC) were analyzed. Moreover, the degradation pathway was identified using an LC-mass spectrometer. This work showed that slag nanocomposite is effective for dye degradation and lowering the overall cost of the Fenton process at a neutral pH.

DOI： 10.1016/j.enmm.2023.100836

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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：Journal of Nuclear Science and Technology  

The Japan Atomic Energy Agency has been developing 9Cr-oxide dispersion strengthened (ODS) steel as a fuel cladding material for sodium-cooled fast reactors (SFRs). Previous studies have formulated the creep rupture equation for 650°C–850°C. However, little data have been obtained above 850°C, and no equation has been formulated. This study conducted creep tests to evaluate creep strength at 700°C–1000°C. Two creep test methods, the internal pressure and ring creep tests under development, were used, and the validation of the ring creep test method was conducted. The results showed that 9Cr-ODS steel undergoes almost no strength change due to the matrix’s phase transformation, and a single equation can express a creep rupture strength from 700°C to 1000°C. In validating the ring creep test method, analysis clarified the effect of stress concentration on the specimen. Plastic deformation occurs at high initial stress and may lead to early rupture. The results will be essential for future creep testing and evaluation of neutron-irradiated 9Cr-ODS steel.

DOI： 10.1080/00223131.2023.2269178

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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  

Metastable β titanium alloys possess excellent strain-hardening capability, but suffer from a low yield strength. As a result, numerous attempts have been made to strengthen this important structural material in the last decade. Here, we explore the contributions of grain refinement and interstitial additions in raising the yield strength of a Ti-12Mo (wt.%) metastable β titanium alloy. Surprisingly, rather than strengthening the material, grain refinement actually lowers the ultimate tensile strength in this alloy. This unexpected and anomalous behavior is attributed to a significant enhancement in strain-induced α’’ martensite phase transformation, where in-situ synchrotron X-ray diffraction analysis reveals that this phase is much softer than the parent β phase. Instead, a combination of both oxygen addition and grain refinement is found to realize an unprecedented strength-ductility synergy in a Ti-12Mo-0.3O (wt.%) alloy. The advantageous effect of oxygen solutes in this ternary alloy is twofold. Firstly, solute oxygen largely suppresses strain-induced transformation to the α’’ martensite phase, even in a fine-grained microstructure, thus avoiding the softening effect of excessive amounts of α’’ martensite. Secondly, oxygen solutes readily segregate to twin boundaries, as revealed by atom probe tomography. This restricts the growth of {332}<113> deformation twins, thereby promoting more extensive twin nucleation, leading to enhanced microstructural refinement. The insights from our work provide a cost-effective rationale for the design of strong yet tough metastable β titanium alloys, with significant implications for more widespread use of this high strength-to-weight structural material.

DOI： 10.1016/j.actamat.2023.119165

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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.61.543

DOI： 10.2320/matertrans.mt-md2022017_references_DOI_TuQpzV6CsZfx6a9NZMIjDoLQAJM

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その他リンク： https://kaken.nii.ac.jp/grant/KAKENHI-PLANNED-18H05481/

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/matertrans.mt-m2021021

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1299/jsmehokkaido.2017.55.29

記述言語：日本語  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.ultramic.2015.07.003

記述言語：日本語  

Three-dimensionalization, i.e., direct representation or fabrication of three-dimensional (3D) objects, is now a key technology in various science and engineering fields. Electron microscopy, a vital nanoscale characterization tool, is no exception, thus various imaging methods have been developed to extend its imaging capabilities from conventional two dimensions to three dimensions. In this article, we focus on electron tomography (ET), which is a typical 3D imaging method using transmission electron microscopy (TEM) or scanning transmission electron microscopy（STEM）, and overview the current status and future prospects of ET and an application of ET to 3D imaging of dislocations in crystalline materials as an practical example.

DOI： 10.5940/jcrsj.57.276

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.jallcom.2014.08.258

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2355/tetsutohagane.100.406

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.ijfatigue.2009.06.006

記述言語：英語  

DOI： 10.2320/matertrans.E2008002

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開催年月日： 2016年6月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東北大学   国名：日本国  

開催年月日： 2015年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：九州大学   国名：日本国  

開催年月日： 2015年9月

記述言語：英語   会議種別：口頭発表（一般）  

国名：ドイツ連邦共和国  

開催年月日： 2015年8月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：弘前市星と森のロマントピア   国名：日本国  

開催年月日： 2015年6月 - 2015年7月

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開催地：国立京都国際会館・京都  

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開催地：国立京都国際会館・京都  

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開催地：東京大学駒場キャンパス・東京  

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開催地：東京大学駒場キャンパス・東京  

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2日、口頭発表

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開催地：東北大学東京分室会議室AおよびB・東京  

開催年月日： 2014年12月

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開催地：種子島・鹿児島   国名：日本国  

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開催地：宮崎市民プラザ・宮崎   国名：日本国  

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開催地：宮崎市民プラザ・宮崎   国名：日本国  

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国名：日本国  

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開催地：名古屋大学 東山キャンパス・名古屋   国名：日本国  

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開催地：名古屋大学 東山キャンパス・名古屋   国名：日本国  

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開催地：名古屋大学 東山キャンパス・名古屋   国名：日本国  

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開催地：名古屋大学 東山キャンパス・名古屋   国名：日本国  

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開催地：北海道大学 札幌キャンパス・北海道   国名：日本国  

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国名：チェコ共和国  

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国名：チェコ共和国  

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開催地：北見工業大学 屈斜路湖研究所・北海道   国名：日本国  

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開催地：北見工業大学 屈斜路湖研究所・北海道   国名：日本国  

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開催地：北見工業大学 屈斜路湖研究所・北海道   国名：日本国  

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国名：スペイン  

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国名：スペイン  

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開催地：Euskalduna Congress Palace, Bilbao, Spain   国名：スペイン  

開催年月日： 2014年3月

記述言語：日本語  

開催地：東京工業大学・東京  

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開催地：東京工業大学・東京  

開催年月日： 2014年3月

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開催地：青山学院大学相模原キャンパス・神奈川   国名：日本国  

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開催地：金沢大学  

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開催年月日： 2013年3月

記述言語：日本語  

開催年月日： 2012年9月

記述言語：日本語  

開催地：愛媛大学・愛媛   国名：日本国  

開催年月日： 2012年9月

記述言語：日本語  

開催地：愛媛大学・愛媛   国名：日本国  

開催年月日： 2012年9月

記述言語：日本語  

開催地：愛媛大学・愛媛   国名：日本国  

開催年月日： 2012年9月

記述言語：日本語  

開催地：愛媛大学・松山大学   国名：日本国  

開催年月日： 2012年8月 - 2012年9月

記述言語：日本語  

開催地：大山研究センター・富山   国名：日本国  

開催年月日： 2012年8月 - 2012年9月

記述言語：日本語  

開催地：大山研究センター・富山   国名：日本国  

開催年月日： 2012年8月 - 2012年9月

記述言語：日本語  

開催地：大山研究センター・富山   国名：日本国  

開催年月日： 2012年6月

記述言語：英語  

国名：日本国  

開催年月日： 2012年6月

記述言語：英語  

国名：日本国  

開催年月日： 2012年6月

記述言語：英語  

国名：日本国  

開催年月日： 2012年5月

記述言語：英語  

国名：日本国  

開催年月日： 2012年5月

記述言語：英語  

国名：日本国  

開催年月日： 2012年5月

記述言語：日本語  

開催地：つくば国際会議場・茨城   国名：日本国  

開催年月日： 2012年5月

記述言語：日本語  

開催地：つくば国際会議場・茨城   国名：日本国  

開催年月日： 2012年5月

記述言語：日本語  

開催地：つくば国際会議場・茨城   国名：日本国  

開催年月日： 2012年3月

記述言語：日本語  

開催地：横浜国立大学常盤台キャンパス・神奈川   国名：日本国  

開催年月日： 2012年3月

記述言語：日本語  

開催地：横浜国立大学常盤台キャンパス・神奈川   国名：日本国  

開催年月日： 2012年3月

記述言語：日本語  

開催地：横浜国立大学常盤台キャンパス・神奈川   国名：日本国  

開催年月日： 2012年3月

記述言語：日本語  

開催地：横浜国立大学常盤台キャンパス・神奈川   国名：日本国  

開催年月日： 2012年3月

記述言語：日本語  

開催地：横浜国立大学常盤台キャンパス・神奈川   国名：日本国  

開催年月日： 2012年3月

記述言語：日本語  

開催地：横浜国立大学常盤台キャンパス・神奈川   国名：日本国  

開催年月日： 2012年3月

記述言語：日本語  

開催地：早稲田大学早稲田キャンパス・東京   国名：日本国  

開催年月日： 2012年1月

記述言語：日本語  

開催地：日本科学未来館・東京   国名：日本国  

開催年月日： 2012年1月

記述言語：日本語  

開催地：日本科学未来館・東京   国名：日本国  

開催年月日： 2011年11月

記述言語：日本語  

開催地：かんぽの宿 那覇レクセンター・沖縄   国名：日本国  

開催年月日： 2011年11月

記述言語：日本語  

開催地：沖縄コンベンションセンター・沖縄   国名：日本国  

開催年月日： 2011年11月

記述言語：日本語  

開催地：沖縄コンベンションセンター・沖縄   国名：日本国  

開催年月日： 2011年11月

記述言語：日本語  

開催地：沖縄コンベンションセンター・沖縄   国名：日本国  

開催年月日： 2011年11月

記述言語：日本語  

開催地：沖縄コンベンションセンター・沖縄   国名：日本国  

開催年月日： 2011年11月

記述言語：日本語  

開催地：沖縄コンベンションセンター・沖縄   国名：日本国  

開催年月日： 2011年11月

記述言語：日本語  

開催地：沖縄コンベンションセンター・沖縄   国名：日本国  

開催年月日： 2011年11月

記述言語：日本語  

開催地：沖縄コンベンションセンター・沖縄   国名：日本国  

開催年月日： 2011年11月

記述言語：日本語  

開催地：沖縄コンベンションセンター・沖縄   国名：日本国  

開催年月日： 2011年9月 - 2011年10月

記述言語：日本語  

開催地：九州大学箱崎キャンパス・福岡   国名：日本国  

開催年月日： 2011年9月

記述言語：英語  

国名：日本国  

開催年月日： 2011年9月

記述言語：英語  

開催地：Senri-Hankyu Hotel, Osaka, Japan   国名：日本国  

開催年月日： 2011年9月

記述言語：英語  

開催地：Senri-Hankyu Hotel, Osaka, Japan   国名：日本国  

開催年月日： 2011年9月

記述言語：英語  

開催地：Senri-Hankyu Hotel, Osaka, Japan   国名：日本国  

開催年月日： 2011年8月

記述言語：日本語  

開催地：樺川荘　本館・香川   国名：日本国  

開催年月日： 2011年8月

記述言語：日本語  

開催地：樺川荘　本館・香川   国名：日本国  

開催年月日： 2011年7月

記述言語：英語  

国名：インド  

開催年月日： 2011年7月

記述言語：英語  

国名：インド  

記述言語：日本語  

開催地：パシフィコ横浜  

記述言語：日本語  

開催地：首都大学東京  

記述言語：日本語  

開催地：首都大学東京  

記述言語：日本語  

開催地：首都大学東京  

記述言語：日本語  

開催地：首都大学東京  

記述言語：日本語  

開催地：首都大学東京  

記述言語：日本語  

開催地：首都大学東京  

記述言語：日本語  

開催地：首都大学東京  

記述言語：日本語  

開催地：首都大学東京  

記述言語：日本語  

開催地：熊本大学  

記述言語：日本語  

開催地：熊本大学  

記述言語：日本語  

開催地：熊本大学  

記述言語：日本語  

開催地：東京工業大学  

記述言語：英語  

記述言語：英語  

記述言語：英語  

記述言語：英語  

国名：日本国  

記述言語：日本語  

開催地：福岡国際会議場  

記述言語：日本語  

開催地：北海道大学  

記述言語：日本語  

開催地：北海道大学  

記述言語：日本語  

開催地：北海道大学  

記述言語：日本語  

開催地：北海道大学  

記述言語：日本語  

開催地：北海道大学  

記述言語：英語  

記述言語：日本語  

開催地：サンヒルズ三河湾、愛知県  

記述言語：日本語  

開催地：サンヒルズ三河湾  

記述言語：日本語  

開催地：サンヒルズ三河湾  

記述言語：日本語  

開催地：サンヒルズ三河湾  

記述言語：日本語  

開催地：釧路工業高等専門学校  

記述言語：日本語  

開催地：東京大学生産技術研究所  

記述言語：日本語  

開催地：宇都宮大学  

記述言語：日本語  

開催地：東京工業大学  

記述言語：日本語  

開催地：ニューウェルシティ宮崎  

記述言語：日本語  

開催地：東京工業大学  

記述言語：日本語  

開催地：早稲田大学  

記述言語：日本語  

開催地：千葉工業大学新習志野キャンパス  

記述言語：日本語  

開催地：千葉工業大学  

記述言語：日本語  

開催地：千葉工業大学  

記述言語：日本語  

開催地：熊本大学黒髪キャンパス  

記述言語：日本語  

開催地：熊本大学  

記述言語：日本語  

開催地：久留米シティプラザ  

記述言語：日本語  

開催地：久留米シティプラザ  

記述言語：日本語  

開催地：北九州国際会議場  

記述言語：日本語  

開催地：北九州国際会議場  

記述言語：英語  

記述言語：日本語  

記述言語：日本語  

記述言語：日本語  

記述言語：日本語  

記述言語：日本語  

記述言語：日本語