「鉄と鋼」に掲載された前1か年の論文を審査し、学術上、技術上最も有益な論文を寄稿した会員に授与

理工学特に金属及びその周辺材料に関連する研究を行い、優れた研究成果、または、発明を行った者で、将来の発展を期待できる若い研究者に贈呈される.

田中 將己氏の研究は、建造物や運輸機器、原子炉などに使用される構造材料の破壊起点であるミクロな亀裂先端の挙動を、高分解能電子顕微鏡を用いて原子尺度で解明しようとするものです。
金属などの構造材料が外部から力を受けて変形し、限界に達すると原子結合が切断され亀裂が発生します。この亀裂の先端が進展する事によって破壊に至ります。破壊は必ずしも一気には進まず、亀裂先端近傍での応力緩和により一定の遅れを示します。この緩和の度合いが、材料の強度を大きく左右し、構造物の最終的な強度をも決めると言っても過言でありません。しかし、これほど重要な課題であるにもかかわらず亀裂先端における応力緩和機構は今日に至るまで完全には解明されておりません。亀裂先端の挙動に関わる領域は、その周囲を含めても原子尺度で測れる程度の広がりに留まるので、問題解決には原子尺度での構造情報が必要です。しかしながら、亀裂先端近傍の格子転位を媒介にした歪み場を、高分解能電子顕微鏡によって原子レベルで構造解析はこれまで困難でした。このことが問題解決を妨げる大きな要因でした。
田中将己氏は、計算機との連携による電子顕微鏡の応用技術の向上により、これまで困難とされてきた格子転位を含む歪み場の高分解能電子顕微鏡による原子尺度の評価が可能になってきたことを踏まえて、亀裂先端の歪み場を原子尺度で実験的に解析して、材料物理学、材料強度学における長年の懸案である、亀裂先端における応力緩和機構を、これまで培われてきた弾性論との整合性をふくめ、解明する事を目指しており、その成果が大いに注目されます。

鉄鋼及びその関連領域において優れた研究業績を挙げている若手研究・技術者に授与

日本金属学会会報「まてりあ」に論文または記事を掲載して，金属及びその周辺材料の学術及び科学技術の振興に顕著な貢献をした者に贈られるものである。

2011年10月に行われたInternational Federation for Heat Treatment and Surface Engineering主催の国際会議において発表時に35歳以下の優れた若手研究者を1名表彰する．総勢50名以上の応募者から事前の論文審査を経て6名が最終選考にかけられた．これら6名を国際会議における発表で審査し，1名を表彰した．

日本金属学会と米国TMSにおける若手研究者の交流を図るために，毎年１～２名程度の若手研究者を相互に推薦・派遣し表彰及び招待講演を行う．

会誌、Materials Transactionsに掲載された学術上または技術上特に優秀な論文で、年齢35歳未満の春秋一般講演発表者を対象とする

Language：English   Publisher：The Japan Institute of Metals and Materials  

<p>The strain-rate dependence of slip persistence in TiZrNbHfTa was investigated using microcantilever bending tests instead of conventional single-crystal tensile tests. These tests were performed using micrometre-sized cantilevers fabricated within a grain of the polycrystalline material, and the ψ–χ relationship was obtained in detail. Bending tests were conducted in two strain rates to determine the ψ–χ relationship. The results showed that the slip plane macroscopically persisted on the {112} plane in the high-strain-rate test, while in the low-strain-rate test, the apparent slip plane roughly coincided with the plane where the maximum shear stress was applied. Detailed tracing of the slip bands, using atomic force microscopy, on the specimen surface showed that the slip plane was microscopically persisted on the {112} plane in high-strain-rate tests, while in low-strain-rate tests, the slip plane often cross-slipped between the {112} and {110} planes.</p>

DOI： 10.2320/matertrans.mt-ma2024010

CiNii Research

Language：Japanese   Publisher：The Japan Institute of Titanium  

<p>The methodology for deriving microscopic stress-strain curves through stress evaluation using HR-EBSD technique and strain evaluation by SEM-DIC method during in situ tensile tests is outlined. A georeferencing operation was used to assign crystallographic and stress information measured by (HR-)EBSD to the corresponding DIC subsets. Based on georeferenced strain and crystallographic information, it is shown that strain evolution trends can be distinguished depending on the phases, the magnitude of the Schmid factor, and the distance from the grain boundary. The microscopic and local stress-strain behavior observed in the Ti-6Al-4V alloy showed considerable variation depending on the location within the microstructure. The local work-hardening rate was calculated from the stress-strain information of each subset and presented as a work-hardening rate map.</p>

DOI： 10.60418/titan.2.1_7

CiNii Research

Publishing type：Research paper (scientific journal)   Publisher：International Journal of Hydrogen Energy  

Enhancement of thermally activated dislocation motion by solute hydrogen (H) has been envisaged in Fe–Cr–Ni austenitic steel through accelerated stress relaxation and a prolonged creep duration. Nevertheless, differences in the imposed stress/strain between the compared non- and H-charged samples at the starts of these mechanical transients, as well as involvements of other obstacles (e.g., alloying elements and forest dislocations), mask the essential effects of H. We performed stress relaxation and strain rate jump tests at multiple stress/strain for Type310S austenitic steel with ∼7600 at ppm H at 296 K. The measured strain rate sensitivity (SRS) was evaluated via a methodology so-called Haasen plot. By screening the latent factors above, primary role of H was revisited: they work as short-range obstacles, hindering the dislocation movement. Multiple H atoms potentially participate in each thermal activation event, giving rise to a stress-equivalent activation volume and a proportionality between H concentration and yield strength.

DOI： 10.1016/j.ijhydene.2024.06.113

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：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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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Materials  

To manufacture metallic components with high wear resistance, treatments such as nitriding and carburising followed by quenching and tempering (NQT and CQT, respectively) are applied to various types of steel to increase the hardness (H) of the friction surface. However, the wear mechanism of the resulting functionally graded materials has not been fully understood. In this study, specimens of industrial 99.82% pure iron treated with NQT at 913 and 1033 K, and CQT at 1203 K, as well as hot-rolled sheets without heat treatment were examined by performing nanoindentation tests to measure changes in their H, reduced Young’s moduli (Er), elastic deformation energies (We), and plastic deformation energies (Wp) along the depth direction. The relationship between Wp/We and the elastic strain resistance (H/Er) can be expressed for all specimens via the equation Wp/We = −1.0 + 0.16 (H/Er)−1. Furthermore, the obtained H/Er av measured at 5 µm intervals based on the specimen profile and wear volume has a good correlation depending to the sliding distance, as confirmed by the results of the ring-on-plate sliding tests conducted for the carbon-treated, nitrogen-treated, and hot-rolled specimens. This study provides a new approach, using H/Er parameters to identify the dominant factors affecting wear resistance at the initial stage of wear that may contribute to the development of wear-resistant materials.

DOI： 10.3390/ma17071567

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Language：Japanese   Publisher：The Iron and Steel Institute of Japan  

<p>Microscopic deformation and fracture behavior of a ferrite-bainite dual phase steel was investigated by the micro-grid method and FE analysis to understand the inherent conditions of plastic instability and ductile fracture. The micro-grid method, which the microscopic strain is measured by the displacement of grids with 500 nm intervals drawn on the specimen surface, clearly revealed that the shear deformation along the lath structure in the bainite phase was seen before reaching the maximum loading point. Then, voids were observed in the ferrite phase adjacent to the ferrite/bainite boundary, where showing higher strain concentration. From the FE analysis with the model simulating actual ferrite-bainite microstructure, stress distribution was seen in the bainite phase, and high stressed regions could cause the shear deformation of the bainite phase. The local shear deformation in the bainite phase decreased strain hardenability and triggered the macroscopic plastic instability. It is considered that the macroscopic plastic instability accelerates the strain localization, and promotes the void nucleation and growth. Ductile fracture path was also visualized by the micro-grids in the ferrite phase along the shear deformation bands which is connecting the high strain regions. Development of shear deformation bands inside the ferrite phase was well simulated with the FE analysis, same as the development of high stressed region in the bainite phase in the early stage. It can be stated, therefore, that plastic instability and ductile fracture of dual phase steel is a structure dependent phenomenon which is strongly controlled by the morphologies of each constituent phases.</p>

DOI： 10.2355/tetsutohagane.tetsu-2023-066

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Language：English   Publisher：The Iron and Steel Institute of Japan  

<p>The strain distribution due to martensitic transformation in a Fe–Ni alloy was investigated using high-precision markers drawn via electron-beam lithography. This study focused on the strain distribution within the lenticular martensite plate, which developed immediately below the martensite start temperature.</p><p>The strain in the central region of lenticular martensite was determined to be greater than that near the interface boundary by measuring the displacement at each intersection of the grid markers. This finding is consistent with the shape strain distribution predicted by the phenomenological theory of martensitic transformation based on the microstructure observations.</p>

DOI： 10.2355/isijinternational.isijint-2023-163

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CiNii Research

Language：English   Publisher：The Japan Institute of Metals and Materials  

<p>This study investigates the mechanical properties of fully-lamellar Ti-6Al-4V, focusing on thermally activated processes behind yielding. Temperature dependences of yield stress, effective stress, activation volume, and activation enthalpy were examined within the temperature range of 77 K to 650 K. The change in the activation volume indicates a change in the deformation mechanism as a thermally activated process. The activation enthalpy in the fully-lamellar Ti-6Al-4V was closer to that of the basal slip in single-crystalline commercially pure Ti, indicating the dominance of basal slip in the fully-lamellar Ti-6Al-4V. Additionally, this study compares the difference in activated slip systems of this alloy with bimodal Ti-6Al-4V and Ti-0.45O, and suggesting changes in deformation mechanisms.</p>

DOI： 10.2320/matertrans.mt-mc2024002

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Language：Japanese   Publisher：The Japan Institute of Metals and Materials  

<p>Microscopic stress-strain curves were obtained by applying stress measurements using the HR-EBSD method and strain measurements using the DIC method to the same field of view in SEM <i>in-situ</i> tensile tests. From the analysis of these microscopic stress-strain curves, yield stress map and work hardening rate map were successfully produced. The relationship between these mechanical property value maps and the microstructure is investigated. The yield stress maps confirm the tendency of the local yield stress to show different values for different grains, but the Schmid factor alone cannot explain the magnitude of the yield stress. When adjacent grains with significantly different Schmid factors deformed cooperatively, the yield stress is found to increase as a result of stress partitioning. Localized regions of extreme work hardening rates were observed in the work hardening rate maps. These regions were located close to grain boundaries with low <i>m</i>′ values where slip transfer was difficult and an interruption of the slip bands was observed. In addition, the rate of increase of GND density with strain was large in these regions. From these results, it can be understood that the extreme work hardening rates are due to increased back stresses caused by the accumulation of dislocations on low <i>m</i>′ grain boundaries.</p>

DOI： 10.2320/jinstmet.j202404

CiNii Research

Language：English   Publisher：The Iron and Steel Institute of Japan  

<p>To understand the influence of composite structures on the brittle-to-ductile transition (BDT) in low-carbon martensite-bainite steel, this study examines the temperature dependence of the impact absorbed energy in five types of steel with identical chemical compositions: fully martensitic steel, fully bainitic steel, and martensite-bainite steels containing 4%, 15%, and 55% bainite fractions, respectively. The BDT temperature was found to be highest for fully martensitic steel, followed by martensite–4% bainite, martensite–15% bainite, martensite–55% bainite, and fully bainitic steel. Despite the significant differences in bainite volume fractions, the BDT temperatures of martensite–15% bainite, martensite–55% bainite, and fully bainitic steel were similar, indicating that the BDT temperature trend cannot be solely explained by the composite rule. To elucidate the trend in BDT temperature based on the shielding theory, the temperature dependence of the 0.2% proof stress was measured for each type of steel. Optical micrographs and the temperature dependence of effective stress showed that dislocations in the bainite phase were preferentially activated, playing a dominant role in determining the yielding behaviour and BDT in the martensite-bainite steels. This behaviour was also associated with the network structure of bainite surrounding the martensite, where the bainite phase underwent plastic deformation immediately after yielding in the steels under investigation.</p>

DOI： 10.2355/isijisss.2024.0_75

CiNii Research

Language：Japanese   Publisher：The Japan Institute of Metals and Materials  

<p>We investigated how dwell fatigue loading accelerates the crack propagation in bi-modal Ti-6Al-4V alloy. A fatigue test was programmed to include displacement holding for only one cycle at several Δ<i>K</i>. We found (1) crack tip strain evolved during the displacement holding, (2) the displacement holding increased fatigue striation spacing, and (3) the strain increment during the displacement holding was linearly correlated with spacing of the displacement-holding-extended striations. These facts indicate that the dwell loading assisted crack opening, which accelerated the crack propagation. Other analyses results and discussion are also presented, in terms of crack propagation mode, crack closure, and dislocation structure.</p><p> </p><p>Mater. Trans. <b>63</b> (2022) 1232-1241に掲載</p>

DOI： 10.2320/jinstmet.j2023022

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

A method for obtaining microscopic and localized stress-strain curves is proposed by combining strain measurements using the digital image correlation (DIC) method with stress measurements using high-resolution electron backscattered diffraction (HR-EBSD). A dataset containing 11 steps of stress–strain information in a single subset was created by applying georeferencing to DIC strain maps and HR-EBSD stress maps measured in a deformation-interrupted microstructure. This analysis allowed us to obtain local stress-strain curves and strain energy maps of polycrystalline nickel alloys. A comparison of the stress-strain curves obtained from any subset in the map revealed that these curves show extremely diverse shapes depending on the location in the microstructure.

DOI： 10.1016/j.scriptamat.2023.115603

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Light Metals  

<p>Impact tests and tensile tests were conducted between 77 K and 450 K in order to elucidate the temperature dependence of absorbed-impact energy, yield stress, effective shear stress, activation volume, and activation enthalpy. The impact-absorbed energy decreased with decreasing test temperature, however, this alloy did not undergo low-temperature embrittlement although it has a bcc structure. Tensile tests showed changes in both the work-hardening rate and the temperature dependence of yield stress at approximately 150 K. This suggests a change in the mechanism behind the plastic deformation at the temperature. The temperature dependence of the activation enthalpy for dislocation glide suggests that the process of climbing over the Peierls potential (kink-pair nucleation) is the dominant mechanism for the dislocation glide from 150 K to 200 K, while the interaction between a dislocation and solute atoms dominantly controls the dislocation glide above 200 K. Superelasticity appears in stress-strain curves tested below 120 K, suggesting that the yielding is governed by transformation-induced plasticity below 120 K. The enhanced toughness at low temperatures in these alloys is discussed from the viewpoint of dislocation shielding theory.</p>

DOI： 10.2464/jilm.73.497

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Scripta Materialia  

The effect of carbon on the persistence of the slip in Fe–3 mass% Si was investigated. We applied micro-sized cantilever bending tests to obtain ψ–χ relationships that enable quantitative analysis of the persistence of the slip. It was demonstrated that the result from decarburized specimens using this method is consistent with those obtained in previous studies from bulk-sized tensile test specimens. This novel method eliminates the difficulty of preparing bulk-sized single-crystal specimens for investigating the persistence of the slip. The persistence of the slip weakened in aged specimens containing 0.016 mass% C and disappeared in quenched specimens with the same carbon content, where wavy slip bands were observed. The reason for these changes in the macroscopically apparent slip plane is explained by the assumption that the frequency of nucleating kink-pair in the competitive {110} planes is a function of the resolved shear stress.

DOI： 10.1016/j.scriptamat.2023.115473

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Repository Public URL： https://hdl.handle.net/2324/7169369

Language：Others   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

<p>To develop microstructure control concepts for ensuring the toughness of high-strength steel plates, basic research was conducted using ferrite single-phase steels with different amounts of C, and the effects of the states of C were investigated along with those of solute N. In this study, Fe-0.017C (mass%) alloy, wherein the state of C was changed to a solid solution, intragranular cementite, and intergranular cementite, were used for microstructural observation, Charpy testing, and fracture surface investigation. The results reveal that the toughness of the intragranular cementite steel was the best, followed by that of solute C steel and intergranular cementite steel. In intergranular cementite steel with significantly inferior toughness, the coarse intergranular cementite leads to dislocation pile-up, initial crack formation, and macroscopic brittle fracture. The brittle fracture of intragranular cementite steel was caused by the deformation twins. It is thought that the fine intragranular cementite only had a minor effect on the crack initiation and dislocation mobility. Twin was also confirmed at the initiation point of brittle fracture in the solute C steel. Hence, it was deduced that the deterioration of toughness caused by solute C resulted from the promotion of twinning, which replaced the dislocation movements. However, the deterioration of toughness caused by solute C was smaller compared with that caused by solute N, which partly caused intergranular fracture. This is attributed to the suppression of intergranular fracture by the presence of a small amount of solute C.</p>

DOI： 10.2355/isijinternational.ISIJINT-2023-027

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Language：English   Publisher：Elsevier  

Body-centred cubic (bcc) high-entropy alloys exhibit high strength. However, their yield behaviour and controlling mechanisms are still ambiguous. In this study, the temperature dependence of the yield stress, effective stress, activation volume, and activation enthalpy in a polycrystalline bcc refractory high-entropy alloy of TiZrNbHfTa were measured by tensile tests at 77–750 K. At temperatures above 650 K, the temperature dependence of the yield stress disappeared, and serration appeared in stress–strain curves. By extrapolating the effective shear stress to 0 K, the Peierls stress was estimated to be 580 MPa. The value was compared with different crystals using the relationship (τ_p)/(μ) and (h)/(b) , where τ_p is the Peierls stress, μ is the shear modulus, h is the distance between the slip planes, and b is the Burgers vector. The (τ_p)/(μ) value in this study was slightly higher than that of other bcc crystals. The activation enthalpy below 260 K corresponds to that of other bcc crystals with high Peierls potentials, suggesting kink-pair nucleation is the controlling mechanism of the dislocation glide in this temperature range. Meanwhile, the activation enthalpy above 260 K deviated from the trendline, indicating the changes in the dislocation glide from the kink-pair nucleation to other one.

CiNii Research

Publishing type：Research paper (scientific journal)   Publisher：Materials Science and Engineering A  

Body-centred cubic (bcc) high-entropy alloys exhibit high strength. However, their yield behaviour and controlling mechanisms are still ambiguous. In this study, the temperature dependence of the yield stress, effective stress, activation volume, and activation enthalpy in a polycrystalline bcc refractory high-entropy alloy of TiZrNbHfTa were measured by tensile tests at 77–750 K. At temperatures above 650 K, the temperature dependence of the yield stress disappeared, and serration appeared in stress–strain curves. By extrapolating the effective shear stress to 0 K, the Peierls stress was estimated to be 580 MPa. The value was compared with different crystals using the relationship [Formula presented] and [Formula presented], where τ<inf>p</inf> is the Peierls stress, μ is the shear modulus, h is the distance between the slip planes, and b is the Burgers vector. The [Formula presented] value in this study was slightly higher than that of other bcc crystals. The activation enthalpy below 260 K corresponds to that of other bcc crystals with high Peierls potentials, suggesting kink-pair nucleation is the controlling mechanism of the dislocation glide in this temperature range. Meanwhile, the activation enthalpy above 260 K deviated from the trendline, indicating the changes in the dislocation glide from the kink-pair nucleation to other one.

DOI： 10.1016/j.msea.2023.144917

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Language：English   Publisher：IOP Publishing  

The effect of high-temperature heat treatment during production on the mechanical property of Si wafer, namely yield stress, was studied through tensile tests of Si single crystals at 1123–1373 K, where stress–strain curves were obtained along the [1¯34], [011], [001], and [1¯11] directions. The critical resolved shear stress showed a remarkable temperature dependence, and it decreased with increasing test temperature. Below 1348 K, the activation enthalpy determined through strain rate jump tests showed no significant difference between crystals made by the Chokralski and the floating zone methods. This indicated that the solute oxygen does not influence the thermally activated dislocation glides. The activation enthalpy of 4.9 eV for a dislocation glide was much higher than that reported by previous studies (2.2 eV at temperatures below 1100 K), indicating that the thermal activation of dislocation glide is different from kink-pair nucleation. It was found that self-diffusion can assist the dislocation glide at temperatures above 1130 K.

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publisher：The Japan Society for Technology of Plasticity  

DOI： 10.32277/plastos.6.61_3

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Language：Japanese   Publisher：The Japan Institute of Metals and Materials  

DOI： 10.2320/materia.61.844

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Language：English   Publisher：The Iron and Steel Institute of Japan  

<p>Effect of crack-tip shielding by dislocations is the most fundamental mechanism governing the fracture toughness of crystalline materials. Brittle-to-ductile transition (BDT) caused by increasing temperature is a general phenomenon observed not only in metals and alloys but also in various crystalline materials such as ionic crystals or semiconductors. The increase of fracture toughness in BDT is closely related to the shielding effect due to dislocations multiplied around a crack-tip. The present paper reviews the fundamental theory of crack-tip shielding and its experimental evidence, and also shows the reason why the nature of interatomic bonding has a remarkable influence on macroscopic fracture toughness, based on the shielding theory.</p><p>Hydrogen embrittlement has attracted much attention in the fields of materials science and mechanical engineering although there still remain many arguments on its mechanism. In this paper, the phenomena being characteristic to hydrogen embrittlement are reviewed, and its mechanism is also discussed from the viewpoint of dislocation shielding.</p>

DOI： 10.2355/isijinternational.isijint-2022-237

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

<p>In this study, the strain distribution in grains with a preferred orientation in a cold-rolled steel plate was investigated. This was done by measuring the amount of strain in a region of the material using nanoscale fine markers applied by a focused ion beam (FIB). We obtained the crystal orientations and strain distributions in the same region using scanning electron microscopy-electron backscatter diffraction and the markers made by the FIB during rolling to a 60% to 70% thickness reduction. The method revealed the strain distributions in the grains with the major preferred orientations (cube:{100}<001>; <i>α</i>-fiber:{100}<011>, {211}<011>; <i>γ</i>-fiber:{111}<011>, {111}<211>). The average strains that accumulated in the grains with different major preferred orientations during cold-rolling were almost the same at thickness reduction in the range of 60%–70%. However, the strain distribution width of the <i>γ</i>-fiber grains was approximately twice that of grains with other orientations. These results suggest that the deformation inhomogeneity during rolling is more pronounced for <i>γ</i>-fiber-oriented grains than for grains with other preferred orientations.</p>

DOI： 10.2355/isijinternational.isijint-2022-275

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

<p>In this study, the cleavage fracture of the C14 Fe₂W Laves phase was investigated by first-principles calculations and crystal orientation analysis using scanning electron microscopy. Trace analysis of the orientations of cleavage planes revealed that cleavage fracture occurred in five types of crystal planes: (0001), {1<span style="text-decoration: overline;">1</span>00}, {11<span style="text-decoration: overline;">2</span>0}, {1<span style="text-decoration: overline;">1</span>01}, and {11<span style="text-decoration: overline;">2</span>2}. Among these fractures, the fracture at (0001) is the most preferable. From, the first-principle calculations of the surface energy for fracture, Young’s modulus, and Poisson’s ratio, the minimum fracture toughness value of 1.62 MPa·m^1/2 was obtained at (0001). The tendency of the calculated fracture toughness to become larger with high indexed planes is almost the same as the frequency of the types of cleavage planes in the trace analysis. It was concluded that the fracture toughness of the C14 Fe₂W Laves phase is controlled by the surface energy for fracture and Young’s modulus.</p>

DOI： 10.2355/isijinternational.isijint-2022-122

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

<p>Resistance to Sulfide Stress Cracking (SSC) caused by local hard zones of pipe inner surface has been required in low alloy linepipe steel. In this study, using two samples with different surface hardness, the detailed SSC initiation behavior was clarified by four-point bend (4PB) SSC tests in which immersion time and applied stress were changed in a sour environment containing 0.15 bar hydrogen sulfide (H₂S) gas. SSC cracks occurred when the applied stress was higher than 90% actual yield strength (AYS) in higher surface hardness samples over 270 HV0.1. From the fracture surface observation of SSC crack sample, it was found that the mechanism gradually shifted from active path corrosion (APC) to hydrogen embrittlement (HE), and that the influence of APC mechanism remained partially in the process of SSC initiation at the tip of corrosion pit or groove. The polarization measurement in the 4PB SSC test showed that the anodic and cathodic reactions (especially cathodic reactions) were activated when the applied stress was 90% AYS or higher. The FEM coupled analysis simulating the stress and strain concentration at the bottom tip of the corrosion groove and the hydrogen diffusion and accumulation was carried out. The principal stress in the tensile direction showed the maximum value at 0.04–0.06 mm away from the tip of the corrosion groove, and the hydrogen accumulation became the maximum. It was analytically found that the SSC crack initiated and propagated with HE mechanism dominated type when the threshold value of about 0.82 ppm is exceeded.</p>

DOI： 10.2355/isijinternational.isijint-2022-236

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

<p>We investigated how dwell fatigue loading accelerates the crack propagation in bi-modal Ti–6Al–4V alloy. A fatigue test was programmed to include displacement holding for only one cycle at several Δ<i>K</i>. We found (1) crack tip strain evolved during the displacement holding, (2) the displacement holding increased fatigue striation spacing, and (3) the strain increment during the displacement holding was linearly correlated with spacing of the displacement-holding-extended striations. These facts indicate that the dwell loading assisted crack opening, which accelerated the crack propagation. Other analyses results and discussion are also presented, in terms of crack propagation mode, crack closure, and dislocation structure.</p>

DOI： 10.2320/matertrans.mt-m2022076

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Japanese Journal of Applied Physics  

We have investigated the effects of the secondary defects caused by ion implantation on wafer strength. The change in wafer strength with the ion dose has been examined after implanting phosphorus or (BF2)+ ions into wafers with and without heat treatment. Ion implantation defects have been observed using transmission electron microscopy after ion implantation with and without subsequent annealing. The three-point bending tests carried out with the ion implanted samples show that the upper yield stress, which represents wafer strength, gradually decreases with the increasing dose in the case of phosphorus ions and rapidly decreases in the case of (BF2)+ ions due to the formation of secondary defects. In addition, the strength of the wafers with a low oxygen concentration is lower than that of the wafers with a high oxygen concentration. However, the rate of decrease in wafer strength with increasing ion dose is not affected by the oxygen concentration; it only depended on the implanted element.

DOI： 10.35848/1347-4065/ac4f4b

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

<p>The temperature dependence of fatigue crack growth in stage IIb was investigated in Ti–0.49 mass%O with an alpha single phase. It was found that the fatigue crack growth rate in stage IIb was temperature independent at temperatures above 300 K. EBSD maps beside the fatigue crack showed that prismatic slips with 〈a〉 dislocations were dominantly activated during the fatigue crack growth. The reason why the prismatic slips were dominantly activated is discussed with numerical crystal plasticity analysis. It was shown that the local strain rate at the notch tip was higher than the macroscopic strain rate, which leads to the suppression of non-prismatic slips at the fatigue crack tip.</p>

DOI： 10.2320/matertrans.mt-m2021211

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

<p>To clarify the formation process of a lamellar microstructure during rolling, we employ a method for following the crystal orientation distribution in the same region before and after the rolling process, in addition, the local strain distribution owing to the formation of the rolled structure was investigated by measuring the amount of strain in the grain from cold rolling using nano-order fine markers applying a focused ion beam (FIB).</p><p>During rolling at a 50% to 70% reduction in thickness, different crystal rotations were observed in the initial grains. A trace analysis of the slip band suggested that the crystal rotation in different directions was caused by the activation of different slip systems in each region. The distribution of the equivalent plastic strain from a 60% to 70% reduction owing to a grain subdivision was examined and compared with the change in crystallographic orientation, suggesting that non-uniform slippage deviating from the Taylor model occurred in the regions where a significant orientation change occurred.</p><p>Furthermore, the strain distribution measured by the marker showed that tensile deformation caused by rolling tended to be suppressed compared to compressive deformation near the grain boundaries inclined toward the rolling direction. These results suggest that the local crystal rotation inside the grain, which leads to a grain subdivision during rolling, is caused by a deviation of the strain tensor inside the grain from the ideal rolling state.</p>

DOI： 10.2355/isijinternational.isijint-2021-316

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

<p>To develop microstructure control concepts for ensuring the toughness of high-strength steel plates, basic research was conducted using ferrite single-phase steels with different amounts of C, and the effects of the states of C were investigated along with those of solute N. In this study, Fe-0.017C (mass%) alloy, wherein the state of C was changed to a solid solution, intragranular cementite, and intergranular cementite, were used for microstructural observation, Charpy testing, and fracture surface investigation. The results reveal that the toughness of the intragranular cementite steel was the best, followed by that of solute C steel and intergranular cementite steel. In intergranular cementite steel with significantly inferior toughness, the coarse intergranular cementite leads to dislocation pile-up, initial crack formation, and macroscopic brittle fracture. The brittle fracture of intragranular cementite steel was caused by the deformation twins. It is thought that the fine intragranular cementite only had a minor effect on the crack initiation and dislocation mobility. Twin was also confirmed at the initiation point of brittle fracture in the solute C steel. Hence, it was deduced that the deterioration of toughness caused by solute C resulted from the promotion of twinning, which replaced the dislocation movements. However, the deterioration of toughness caused by solute C was smaller compared with that caused by solute N, which partly caused intergranular fracture. This is attributed to the suppression of intergranular fracture by the presence of a small amount of solute C.</p>

DOI： 10.2355/tetsutohagane.TETSU-2021-076

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

<p>The effect of tempering on uniform elongation was investigated for fully lath martensitic steels with 0.2% C by mass. Stress–strain curves were obtained from specimens tempered at 100, 200, 300 and 400°C. Although total elongation rarely depends on the tempering temperature, the uniform elongation decreased while local elongation increased with the tempering temperature. It was found, using precision markers drawn on the specimen surface, that the distribution of the equivalent plastic strain developed during uniform deformation was inhomogeneous in the specimen tempered at 200°C and relatively homogenous in the specimen tempered at 300°C. Finite element analysis suggests that the uniform elongation depends on the volume fraction that continues elastic deformation even after macroscopic yielding. Therefore, the experimental results showing a decrease in the uniform elongation with tempering temperature can be explained by the decrease in the volume fraction that continues elastic deformation immediately after the macroscopic yielding, which is a deformation character specific to low temperature tempered martensitic steels. The range of variation in nanohardness decreased with the tempering temperature, suggesting that the variation in the local yield stress also decreases with the tempering temperature.</p>

DOI： 10.2355/isijinternational.ISIJINT-2021-287

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DOI： 10.1016/j.prostr.2022.12.184

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

<p>Resistance to Sulfide Stress Cracking (SSC) caused by local hard zones of pipe inner surface has been required in low alloy linepipe steel. In this study, using two samples with different surface hardness, the detailed SSC initiation behavior was clarified by four-point bend (4PB) SSC tests in which immersion time and applied stress were changed in a sour environment containing 0.15 bar hydrogen sulfide (H₂S) gas. SSC cracks occurred when the applied stress was higher than 90% actual yield strength (AYS) in higher surface hardness samples over 270 HV0.1. From the fracture surface observation of SSC crack sample, it was found that the mechanism gradually shifted from active path corrosion (APC) to hydrogen embrittlement (HE), and that the influence of APC mechanism remained partially in the process of SSC initiation at the tip of corrosion pit or groove. The polarization measurement in the 4PB SSC test showed that the anodic and cathodic reactions (especially cathodic reactions) were activated when the applied stress was 90% AYS or higher. The FEM coupled analysis simulating the stress and strain concentration at the bottom tip of the corrosion groove and the hydrogen diffusion and accumulation was carried out. The principal stress in the tensile direction showed the maximum value at 0.04-0.06 mm away from the tip of the corrosion groove, and the hydrogen accumulation became the maximum. It was analytically found that the SSC crack initiated and propagated with HE mechanism dominated type when the threshold value of about 0.82 ppm is exceeded.</p>

DOI： 10.2355/tetsutohagane.tetsu-2022-013

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Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/ma14237217

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DOI： 10.2355/tetsutohagane.TETSU-2021-069

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.scriptamat.2021.113895

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DOI： 10.2320/matertrans.MT-M2020321

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DOI： 10.2320/matertrans.MT-M2020399

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DOI： 10.2355/isijinternational.ISIJINT-2020-757

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/isijinternational.ISIJINT-2020-616

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.4028/www.scientific.net/MSF.1016.1443

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.msea.2020.140211

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DOI： 10.1016/j.msea.2020.140211

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/isijinternational.ISIJINT-2020-158

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1149/2162-8777/abbcb4

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/isijinternational.ISIJINT-2019-754

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2497/jjspm.67.173

Language：Others   Publishing type：Research paper (scientific journal)  

© 2020 Japan Society of Powder and Powder Metallurgy. In the present study, we have examined the wear properties of the sintered pure iron subjected to two distinct heat treatments such as nitriding-quenching (NQ) and carburizing-quenching (CQ). Based on our current observations, the martensite layer was formed on the surface layer following each treatment, whereas the hardness of the NQ martensite was much higher than that of the CQ one. The wear of the CQ specimen was slightly smaller than that of the NQ martensite, despite the lower value of the initial hardness. Meanwhile, the hardness of the CQ surface after the sliding tests significantly elevated relative to the NQ surface resulting in the better wear resistance. EBSD analysis demonstrated that the plastic deformation on the CQ surface along the sliding direction. Furthermore, the micro area X-ray diffraction along the surface layer of the CQ surface showed that a small amount of the retained austeite which reduced locally during the test. Therefore, the CQ-treated surface showed the excellent wear resistivity due to the surface hardening by the stress-induced transformation of the retained austenite dispersed in the martensite, in addition to the strain hardening of the martensite itself. In contrast, the worn surface of the NQ specimen showed slight plastic deformations of the ferrite grains beneath the martensite layer, but not in the surface martensite layer. This deformation under the martensite layer was due to the hardness gap between inward and the heat-treated surface, and might contribute to form the concave profile on the sliding surface. Consequently, this study could demonstrate such the difference in the wear mechanisms between the CQ and the NQ specimens.

DOI： 10.2497/jjspm.67.173

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.7567/1347-4065/ab43a9

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1149/2162-8777/ab9a59

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.7567/1347-4065/ab43a9

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1149/2162-8777/ab9a59

Language：Others   Publishing type：Research paper (scientific journal)  

Investigation of strain redistribution mechanism in α titanium by image-based crystal plasticity analysis
Abstract: Mechanisms of strain localization and localized activation of slip systems in α titanium were investigated using a crystal plasticity finite element (CPFE) method. A microscopic image of polycrystalline α titanium was obtained by electron back scatter diffraction (EBSD), and the data was converted from the microscopic image into the geometric model for the CPFE analysis. The uniaxial tensile deformation of the model was numerically reproduced by the CPFE method employing a dislocation density based constitutive equation. The results showed that the strain distribution corresponds well with that obtained by the experiment when the ratio of critical resolved shear stress (CRSS) employed in the numerical simulation is basal:prismatic ⟨a⟩:1st-pyramidal ⟨a⟩:1st-pyramidal ⟨c + a⟩:2nd-pyramidal ⟨c + a⟩ = 1.0:1.0:1.3:2.0:2.0. Next, numerical simulations were performed by changing the ratio of CRSS among the slip systems but keeping all other conditions the same as those of the above uniaxial tensile analysis. The results showed that strain redistribution typically occurs between hard and soft regions with high and low CRSSs for the primary slip systems; this redistribution resulted in a localized higher strain and activation of slip systems. However, localized activation of slip systems was observed even in slip systems with higher CRSS; the mechanism could be explained by the strain redistribution in the tensile direction. Graphical abstract: [Figure not available: see fulltext.].

DOI： 10.1140/epjb/e2019-100238-3

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.ME201902

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.M2019046

Language：Others   Publishing type：Research paper (scientific journal)  

Investigation of strain redistribution mechanism in α titanium by image-based crystal plasticity analysis
Abstract: Mechanisms of strain localization and localized activation of slip systems in α titanium were investigated using a crystal plasticity finite element (CPFE) method. A microscopic image of polycrystalline α titanium was obtained by electron back scatter diffraction (EBSD), and the data was converted from the microscopic image into the geometric model for the CPFE analysis. The uniaxial tensile deformation of the model was numerically reproduced by the CPFE method employing a dislocation density based constitutive equation. The results showed that the strain distribution corresponds well with that obtained by the experiment when the ratio of critical resolved shear stress (CRSS) employed in the numerical simulation is basal:prismatic ⟨a⟩:1st-pyramidal ⟨a⟩:1st-pyramidal ⟨c + a⟩:2nd-pyramidal ⟨c + a⟩ = 1.0:1.0:1.3:2.0:2.0. Next, numerical simulations were performed by changing the ratio of CRSS among the slip systems but keeping all other conditions the same as those of the above uniaxial tensile analysis. The results showed that strain redistribution typically occurs between hard and soft regions with high and low CRSSs for the primary slip systems; this redistribution resulted in a localized higher strain and activation of slip systems. However, localized activation of slip systems was observed even in slip systems with higher CRSS; the mechanism could be explained by the strain redistribution in the tensile direction. Graphical abstract: [Figure not available: see fulltext.].

DOI： 10.1140/epjb/e2019-100238-3

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.ME201902

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.M2019046

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DOI： 10.2355/tetsutohagane.TETSU-2018-098

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DOI： 10.2320/matertrans.M2018251

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DOI： 10.4028/www.scientific.net/MSF.941.1479

Language：Others   Publishing type：Research paper (other academic)  

Temperature dependence of the yield stress in α-titanium investigated with crystal plasticity analysis
© 2018 Trans Tech Publications, Switzerland. The effect of the activated slip systems on the temperature dependence of yield stress was investigated in α-Ti by using crystal plasticity finite element method. A model for finite element analysis (FEA) was constructed based on experimental results. The displacement in FEA was applied up to the nominal strain of 4% which is the same strain as the experimental one. Stress-strain curves were obtained, which corresponds to experimental data taken every 50 K between 73 K and 673 K. The used material constants which are temperature dependent were elastic constants, and lattice friction stresses. The lattice friction stresses of basal slip systems were set to be higher than that of pyramidal slip systems at 73 K. Then, the lattice friction stresses were set to be closer as the temperature increases. It was found that the activation of slip systems is strong temperature dependent, and that the yield stress depends on the number of active slip systems.

DOI： 10.4028/www.scientific.net/MSF.941.1474

Language：Others   Publishing type：Research paper (other academic)  

Temperature dependence of the yield stress in α-titanium investigated with crystal plasticity analysis
© 2018 Trans Tech Publications, Switzerland. The effect of the activated slip systems on the temperature dependence of yield stress was investigated in α-Ti by using crystal plasticity finite element method. A model for finite element analysis (FEA) was constructed based on experimental results. The displacement in FEA was applied up to the nominal strain of 4% which is the same strain as the experimental one. Stress-strain curves were obtained, which corresponds to experimental data taken every 50 K between 73 K and 673 K. The used material constants which are temperature dependent were elastic constants, and lattice friction stresses. The lattice friction stresses of basal slip systems were set to be higher than that of pyramidal slip systems at 73 K. Then, the lattice friction stresses were set to be closer as the temperature increases. It was found that the activation of slip systems is strong temperature dependent, and that the yield stress depends on the number of active slip systems.

DOI： 10.4028/www.scientific.net/MSF.941.1474

Language：Japanese   Publishing type：Research paper (scientific journal)  

Development of a EBSD-FEM data conversion interface and the image-based crystal plasticity analysis

DOI： 10.1299/transjsme.17-00559

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.7567/JJAP.57.035501

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/tetsutohagane.TETSU-2017-067

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.4028/www.scientific.net/MSF.941.1479

Language：English   Publishing type：Research paper (scientific journal)  

Temperature dependence of activation volume on Cu content of ultra-low carbon steel
The temperature dependence of the yield stress, effective stress and activation volume on the Cu content in steel was assessed using polycrystalline ultra-low carbon steels with 0.5, 1 and 2 mass&#37; Cu added. A small hump was seen in the effective stress–temperature curve for ultra-low carbon steel, which has also been reported for high-purity single-crystal iron. The effective stress was found to decrease with increasing the Cu content. The activation volume was found to be linearly related to the temperature at low temperatures for all types of specimens considered. The activation volume was found to increase abruptly at a certain temperature, which increased with increasing the Cu content. The change in the relationship of the activation volume to temperature is discussed in this paper with respect to the thermally activated process of dislocation glide from the Peierls mechanism to the interaction between dislocations and solute Cu atoms.

DOI： 10.1080/14786435.2017.1359423

Other Link： http://dx.doi.org/10.1080/14786435.2017.1359423

Language：English   Publishing type：Research paper (scientific journal)  

Temperature dependence of activation volume on Cu content of ultra-low carbon steel
The temperature dependence of the yield stress, effective stress and activation volume on the Cu content in steel was assessed using polycrystalline ultra-low carbon steels with 0.5, 1 and 2 mass% Cu added. A small hump was seen in the effective stress–temperature curve for ultra-low carbon steel, which has also been reported for high-purity single-crystal iron. The effective stress was found to decrease with increasing the Cu content. The activation volume was found to be linearly related to the temperature at low temperatures for all types of specimens considered. The activation volume was found to increase abruptly at a certain temperature, which increased with increasing the Cu content. The change in the relationship of the activation volume to temperature is discussed in this paper with respect to the thermally activated process of dislocation glide from the Peierls mechanism to the interaction between dislocations and solute Cu atoms.

DOI： 10.1080/14786435.2017.1359423

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.msea.2017.06.070

Other Link： http://dx.doi.org/10.1016/j.msea.2017.06.070

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DOI： 10.1016/j.msea.2017.06.084

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DOI： 10.2320/matertrans.M2016363

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.msea.2016.11.045

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/14786435.2016.1183828

Other Link： http://dx.doi.org/10.1080/14786435.2016.1183828

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/tetsutohagane.TETSU-2015-099

Language：Japanese  

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/tetsutohagane.TETSU-2015-113

Language：English   Publishing type：Research paper (scientific journal)  

Transmission electron microscopy of bulk specimens over 10μm in thickness
© 2015 The Authors. We succeeded the observation of microstructures in bulk-sized specimens of over 10. μm in thickness by employing a technique that combines transmission electron microscopy (TEM) with energy-filtered imaging based on electron energy-loss spectroscopy (EELS). This method is unique in that it incorporates the inelastically scattered electrons into the imaging process. Using this technique, bright and sharp images of dislocations in crystalline silicon specimens as thick as 10. μm were obtained. A calibration curve to determine foil thickness of such a thick specimen was also derived. This method simply extends the observable thickness range in TEM. If combined with tilt series of observation over a significant range of angle, it will disclose three dimensional nanostructures in a μm-order block of a specimen, promoting our understanding of the controlling mechanisms behind various bulky material properties.

DOI： 10.1016/j.ultramic.2015.09.001

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.scriptamat.2015.09.004

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1093/jmicro/dfv032

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DOI： 10.14723/tmrsj.40.227

Other Link： http://doi.org/10.14723/tmrsj.40.227

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/srep13126

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DOI： 10.2355/tetsutohagane.100.1267

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/tetsutohagane.100.1140

Other Link： http://dx.doi.org/10.2355/tetsutohagane.100.1140

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.msea.2014.06.007

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/isijinternational.54.1735

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.msea.2014.06.007

Other Link： http://dx.doi.org/10.1016/j.msea.2014.06.007

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.4028/www.scientific.net/AMR.922.706

Other Link： http://dx.doi.org/10.4028/www.scientific.net/AMR.922.706

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.msea.2013.12.100

Other Link： http://dx.doi.org/10.1016/j.msea.2013.12.100

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DOI： 10.1080/09500839.2013.872811

Other Link： http://dx.doi.org/10.1080/09500839.2013.872811

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DOI： 10.1016/j.msea.2013.09.072

Other Link： http://dx.doi.org/10.1016/j.msea.2013.09.072

Language：English  

Recent developments in the application of electron tomography for characterizing microstructures in crystalline solids are described. The underlying principles for electron tomography are presented in the context of typical challenges in adapting the technique to crystalline systems and in using diffraction contrast imaging conditions. Methods for overcoming the limitations associated with the angular range, the number of acquired images, and uniformity of image contrast are introduced. In addition, a method for incorporating the real space coordinate system into the tomogram is presented. As the approach emphasizes development of experimental solutions to the challenges, the solutions developed and implemented are presented in the form of examples. (C) 2013 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.matchar.2013.09.016

Language：English   Publishing type：Research paper (scientific journal)  

Plastic deformation of fully pearlitic steels was investigated using a multiscale approach: experimentally, the finite element method and molecular dynamics. This paper is the first in a series of three papers demonstrating the strain distribution in uniaxial tensile deformation with high-precision markers drawn by electron beam lithography. Strain was measured at loads of 1.98 kN, 2.21 kN and 2.28 kN in tensile deformation. Scanning electron microscopy (SEM) images and strain maps show the plastic deformation of cementite lamellae and homogenous plastic deformation under uniaxial tensile deformation in the area where the cementite lamellae are aligned in the tensile direction. The areas where strain was enhanced were both block/colony boundaries and the areas where the cementite lamellae are inclined approximately 45 degrees to the tensile direction. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msea.2013.09.072

Language：English  

DOI： 10.1016/j.matchar.2013.09.016

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.msea.2013.09.032

Other Link： http://dx.doi.org/10.1016/j.msea.2013.09.032

Language：English   Publishing type：Research paper (scientific journal)  

Elasto-plastic deformations in the microstructures of pearlite are studied by finite-element analyses. Various models for the lamellar structure are made and the material properties of cementite and ferrite are established. Deformation of a bare specimen of cementite is unstable immediately after the yield point, while cementite lamellae show some stability when they are layered with ferrite. When higher values of yield stress and strain hardening are used for ferrite phase, cementite deforms well beyond the elastic range and the distribution of plastic strain is not concentrated. These results show that not only the layered structure but also the improved mechanical property of fine lamellae of ferrite contribute largely to stable deformation in the pearlite microstructure. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msea.2013.09.032

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.MH201319

Other Link： http://dx.doi.org/10.2320/matertrans.MH201319

Language：English  

DOI： 10.2320/matertrans.MPR2013906

Language：English   Publishing type：Research paper (scientific journal)  

Brittle-to-ductile transitions (BDT) in fine-grained Ti added ultra-low carbon steels were investigated. Temperature dependences of impact absorbed energy were measured using specimens with grain sizes of 0.4, 2, 9 and 70 mu m of which the grain sizes were controlled by heat treatments after five cycles of accumulative roll-bonding process. Although the BDT temperatures were decreased with the decrease in the grain size, the shape of BDT curves in fine-grained steels are different from those of coarse grains. Specimens with coarse grains show abrupt increase in the absorbed energy at the BDT temperature while fine-grained steels exhibit slight jump of absorbed energy at the BDT temperature and then the energy gradually increases with temperature, showing the enhancement of toughness at low temperatures in fine-grained steels. In the present paper, the characteristic BDT in fine-grained steels was discussed in terms of the thermally activated process of dislocation glide.

DOI： 10.2320/matertrans.MH201319

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/tetsutohagane.98.667

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.4028/www.scientific.net/AMR.409.243

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1179/1749514812Z.00000000029

Language：English  

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Language：Japanese  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Synopsis: The brittle-to-ductile transition (BDT) behaviour in nickel-free austenitic stainless steel with high nitrogen was investigated. Fall-weight impact tests revealed that Fe-25mass%Cr-1.1 mass%N austenitic steel exhibits a sharp BDT behaviour in spite of an fcc alloy. The aspects of plastic deformation after the impact tests indicate that the BDT observed in this austenitic steel is induced by poor ductility at low temperatures as is the same as that in ferritic steels. In order to measure the activation energy for the BDT, the strain rate dependence of the BDT temperature was examined by using four-point bending tests. The weak dependence of the BDT temperature on the strain rate was observed. The Arrhenius plot of the BDT temperature against the strain rate elucidated that the activation energy for the BDT of Fe-25mass%Cr-1.1mass%N is much higher than that of low carbon ferritic steels. The origins of such distinct BDT behaviour and its large value of the activation energy in this high-nitrogen steel are discussed in terms of the reduction of dislocation mobility at low temperatures due to the interaction between glide dislocations and nitrogen solute atoms.

DOI： 10.2355/tetsutohagane.98.237

Language：Japanese  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

The brittle-to-ductile transition (BDT) behaviour in nickel-free austenitic stainless steel with high nitrogen was investigated. Fall-weight impact tests revealed that Fe-25mass%Cr-1.1mass%N austenitic steel exhibits a sharp BDT behaviour in spite of an fcc alloy. The aspects of plastic deformation after the impact tests indicate that the BDT observed in this austenitic steel is induced by poor ductility at low temperatures as is the same as that in ferritic steels. In order to measure the activation energy for the BDT, the strain rate dependence of the BDT temperature was examined by using four-point bending tests. The weak dependence of the BDT temperature on the strain rate was observed. The Arrhenius plot of the BDT temperature against the strain rate elucidated that the activation energy for the BDT of Fe-25mass%Cr-1.1mass%N is much higher than that of low carbon ferritic steels. The origins of such distinct BDT behaviour and its large value of the activation energy in this high-nitrogen steel are discussed in terms of the reduction of dislocation mobility at low temperatures due to the interaction between glide dislocations and nitrogen solute atoms.

DOI： 10.2355/isijinternational.52.915

Language：English  

DOI： 10.2355/isijinternational.52.704

Language：English  

Fundamental mechanism governing the fracture toughness of materials is reviewed in terms of a concept of the interaction between a crack and dislocations. The mechanism behind brittle-to-ductile transition (BDT) is demonstrated using a simple model based on dislocation dynamics and the theory of crack-tip shielding by dislocations. The effects of dislocation mobility as well as dislocation sources on the BDT behavior are discussed, which enables us to understand the various factors such as grain refinement influencing fracture toughness.

DOI： 10.2355/isijinternational.52.704

Language：Japanese  

Other Link： http://doi.org/10.2472/jsms.61.169

Language：Japanese   Publishing type：Research paper (scientific journal)  

In order to investigate the mechanism behind the improvement of fracture toughness in ultrafinegrained metals at low temperatures, the strain rate dependence of the transition of dislocationsources from crack tips to grain boundaries is studied by the combination of molecular dynamicssimulations and the linear elastic theory. As the strain rate decreases, grain boundaries becomeanother stress consented site due to the pile-up of dislocations against the grain boundaries. Theamount of stress concentration became larger than that of crack tip as the number of dislocationsemitted from the crack tip increases. It was clearly indicated that dislocations were impinged intothe grain boundary when a new dislocation was emitted from there. It indicates the transition ofdislocation sources from the crack tip to grain boundaries at lower applied stresses. The distributionof dislocations between the crack tip and grain boundary is strongly related to the strain rate
namely, a larger number of dislocations are distributed very close to the crack tip as the strain rate increases.It induces the smaller stress concentration at the grain boundary since the number of piling-updislocations is decreased around the grain boundary. Consequently, as the strain rate increases, thematerial becomes brittle, indicating that it will fail in a brittle mode and no longer deform plastically. © 2012 The Society of Materials Science, Japan.

DOI： 10.2472/jsms.61.169

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.4028/www.scientific.net/MSF.706-709.1841

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ultramic.2011.03.021

Other Link： http://dx.doi.org/10.1016/j.ultramic.2011.03.021

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevB.83.214113

Other Link： http://dx.doi.org/10.1103/PhysRevB.83.214113

Language：English   Publishing type：Research paper (scientific journal)  

The effect of aluminium concentration on a brittle-to-ductile transition (BDT) has been investigated in Fe-Al single crystals. The BDT temperatures in Fe-4mass%Al and Fe-8mass%Al crystals with < 100 > specimen axis were measured by an instrumental falling weight impact tester, indicating that the BDT temperature in Fe-8%Al is higher than that in Fe-4%Al. Twin-twin intersections were seen on fracture surfaces in Fe-8%Al tested at low temperatures, which shows that the intersection was the origin of a brittle fracture. In order to highlight the effect of deformation twinning on the BDT behaviour, specimens with the < 110 > axis were also employed to suppress the onset of deformation twinning during the impact tests. The BDT temperature in Fe-8%Al was found to be decreased by suppressing deformation twinning, which indicates that deformation twinning is a key mechanism behind increasing the BDT temperature in Fe-Al single crystals. A model to explain the increase in the BDT temperature with aluminium content is also presented.

DOI： 10.2355/isijinternational.51.999

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/isijinternational.51.999

Other Link： http://dx.doi.org/10.2355/isijinternational.51.999

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.scriptamat.2010.12.032

Language：Japanese   Publishing type：Research paper (scientific journal)  

Fundamental mechanism governing the fracture toughness of materials is reviewed in terms of a concept of the interaction between a crack and dislocations. The mechanism of brittle-to-ductile transition (BDT) is demonstrated using a simple model based on dislocation dynamics and the theory of crack-tip shielding by dislocations. The effects of dislocation mobility as well as dislocation sources on the BDT behavior are discussed, which enables us to understand the various factors such as grain refinement influencing fracture toughness.

DOI： 10.2355/tetsutohagane.97.195

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/tetsutohagane.97.195

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.scriptamat.2010.11.035

Language：English   Publishing type：Research paper (scientific journal)  

Crack tip dislocations in silicon single crystals were observed by combining high-voltage electron microscopy and electron tomography. Cracks were introduced by an indentation method and dislocations were introduced around the crack tip by keeping the indented sample at high temperatures for several hours. The number of dislocations emitted from the crack tip was controlled by changing the holding time of the indented specimen at high temperatures. The dislocations observed were characterized in detail. It was found that primary emitted dislocations all had the same Burgers vectors and that some dislocation segments cross-slipped around the crack. The local stress intensity factor due to dislocations was calculated, basing on the dislocation character obtained in this study, indicating that emitted dislocations shields mode I, H and III stress intensity at the crack tip. After the emission of the number of those dislocations, dislocations with another Burgers vector were emitted around the crack. It was found that those dislocations accommodate mode II and III stress components which are the excess shielding fields due lathe dislocations primary emitted from the crack tip. [doi:10.2320/matertrans.MB201024]

DOI： 10.2320/matertrans.MB201024

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.MB201024

Other Link： http://dx.doi.org/10.2320/matertrans.MB201024

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1557/jmr.2010.99

Other Link： http://dx.doi.org/10.1557/jmr.2010.99

Language：English   Publishing type：Research paper (scientific journal)  

The three-dimensional structure of crack tip dislocations in single crystal silicon was observed by combining high-voltage electron microscopy and tomography. It was revealed that dislocations cross-slipped proximal to the crack tip even in the initial stages of plastic deformation. The local stress intensity factor along the crack front was calculated by taking into account the experimentally determined dislocation character. Based on these observations and calculations, a model to account for the sequential multiplication of dislocation sources along the crack front is proposed.

DOI： 10.1557/jmr.2010.99

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.scriptamat.2010.09.033

Language：English   Publishing type：Research paper (scientific journal)  

Ti-matrix composites reinforced with Al2O3 fractions of up to 50 wt.% were fabricated by cold consolidation of powder mixtures using high-pressure torsion (HPT). The grain size of the Ti matrix was reduced to similar to 100 nm. A relative density greater than similar to 99 % was attained for composites containing up to 30 % Al2O3 following the rule of mixture. The Vickers microhardness increased with an increase in the Al2O3 fraction but the bending stress and ductility decreased. The HPT-processed composites exhibited an abrupt increase in the hardness when they were annealed at 800-900 K, indicating a successful achievement of consolidation.

DOI： 10.4149/km_2011_1_85

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.4149/km_2011_1_85

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1557/JMR.2010.0308

Other Link： http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7952549&fulltextType=RA&fileId=S0884291400035792

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.4028/www.scientific.net/MSF.633-634.471

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)  

A novel specimen holder that enables in situ observation of crack-tip deformation and/or fracture under a controlled environment is developed for a high-voltage electron microscope (HVEM). A window-type environmental cell (EC) that incorporates a uniaxial straining apparatus is built into a side-entry-type single-tilt specimen holder. The gas control in EC, straining apparatus design, limited field of view for crack-tip observation, and specimen preparation for the specimen holder are presented in detail. Experimental results successfully demonstrate that the developed specimen holder is quite useful for the dynamic observation of crack-tip deformation and/or fracture subjected to a hostile environment, such as hydrogen gas. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ultramic.2010.07.011

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.4028/www.scientific.net/MSF.654-656.1299

Language：English   Publishing type：Research paper (other academic)  

The brittle-to-ductile transition (BDT) in Czochralski (CZ) grown silicon single crystals and floating-zone (FZ) grown silicon single crystals was investigated by three-point bending. The temperature dependence of the apparent fracture toughness was measured in three different cross-head speeds. It was found that the BDT temperature in the CZ silicon crystal was higher than that in FZ silicon crystal, suggesting that the solute oxygen decreases dislocation mobility. However, the activation energies obtained from the strain rate dependence of the BDT temperatures were nearly the same in both the CZ and FZ silicon crystals, indicating that the dislocation mobility is not influenced by the solute oxygen. In this paper, the origin of the difference in the BDT temperature is discussed, focusing the role of the solute oxygen on the dislocation glide.

DOI： 10.4028/www.scientific.net/MSF.654-656.1299

Language：Others  

Effect of gaseous hydrogen on cyclic slip behavior around a stage i fatigue crack tip in an iron alloy

Language：English   Publishing type：Research paper (scientific journal)  

Three-dimensional structures of crack-tip dislocations in silicon crystals have been examined by combining scanning transmission electron microscopy and computed tomography. Cracks were introduced by a Vickers hardness tester at room temperature, and the sample was heated at 823 K for 1 h in order to introduce dislocations around the crack tips. Dislocation segments cut out from loops were observed around the crack tip, the three-dimensional structure of which was characterized by using by electron tomography. Their Burgers vectors including the sings were also determined by oscillating contrasts along dislocations. In order to investigate the effect of the dislocations on fracture behaviours, local stress intensity factor due to one dislocation was calculated, which indicates the dislocations observed were shielding type to increase fracture toughness.

DOI： 10.1093/jmicro/dfq031

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.M2010048

Other Link： http://dx.doi.org/10.2320/matertrans.M2010048

Language：Japanese   Publishing type：Research paper (scientific journal)  

The effect of hydrogen on local cyclic behavior around an oblique fatigue crack tip in singlecrystalline Fe-3.2wt.%Si alloy is precisely investigated by using cross-sectional transmission electron microscopy (TEM). The observation successfully reveals that the crack propagation is strongly correlated to the formation of dislocation cell structure in an inert atmosphere, whereas no cell structure is formed around the crack tip in a hydrogen atmosphere.

DOI： 10.1299/kikaia.76.1002

Language：Japanese  

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1299/kikaia.76.1002

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.4028/www.scientific.net/MSF.654-656.2307

Language：English   Publishing type：Research paper (other academic)  

Pure Ti powders were subjected to ball milling and subsequently high-pressure torsion (HPT) for consolidation. It is found that a fully dense (99.9%) disc with ultrafine grained structure (similar to 50-300 nm) was produced. The strength and ductility were well comparable to those of ball-milled Ti-6%Al-4%V powders after hot roll sintering.

DOI： 10.4028/www.scientific.net/MSF.654-656.1239

Language：English   Publishing type：Research paper (other academic)  

High-pressure torsion (HPT) was conducted on commercial grade pure titanium (99.4%) by applying pressures in a wide range from 1.2 to 40 GPa. When the microhardness was plotted against equivalent strain, the hardness saturates to a constant level at each applied pressure. Such a level at the saturation depends on the applied pressure: for up to the pressure of 4 GPa, the saturation level is independent of the pressure but, for the pressures above 4 GPa, the hardness gradually increases with pressure because of the formation of an omega phase. Bending tests showed that an excellent ductility as well as high bending strength was achieved for the sample processed at 2 GPa. The bending ductility was reduced for the sample at 6 GPa because of the w phase formation.

DOI： 10.4028/www.scientific.net/AMR.89-91.171

Language：English   Publishing type：Research paper (other academic)  

Three-dimensional structure of crack tip dislocations were investigated by combining scanning transmission electron microscopy (STEM) and electron tomography (ET) in silicon single crystals. P-type (001) silicon single crystals were employed. < 110 > cracks were introduced from an indent on the (001) surface. The specimen was heated at 873K in order to introduce dislocations at the crack tips. The specimen was thinned to include the crack tip in the foil by an iron milling machine. STEM-ET observation revealed the three-dimensional structure of crack tip dislocations. Their Burgers vectors were determined by using an invisibility criterion. The local stress intensity factor was calculated using the dislocation characters obtained in the observation in this study, indicating that the dislocations observed were mode II shielding type dislocations.

DOI： 10.4028/www.scientific.net/MSF.654-656.2307

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.4028/www.scientific.net/MSF.654-656.1239

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.actamat.2009.11.040

Language：Japanese  

Language：English   Publishing type：Research paper (other academic)  

The brittle-to-ductile transition (BDT) behaviour was investigated in low carbon steel deformed by an accumulative roll-bonding (ARB) process. The temperature dependence of its fracture toughness was measured by conducting four-point bending tests at various strain rates. The fracture toughness increased while the BDT temperature decreased in the specimens deformed by the ARB process. Arrhenius plots between the BDT temperatures and the strain rates indicated that the activation energy for the BDT did not change due to the deformation with the ARB process. It indicated that the decrease in the BDT temperature by grain refining was not clue to the reduction in the dislocation mobility with respect to short-range barriers. Quasi-three-dimensional simulations of discrete dislocation dynamics indicated that the decrease in the number of dislocation sources decreases in the BDT temperature. The roles of grain boundaries will be also discussed in order to explain the decrease in the BDT temperature.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Local cyclic slip behavior around an oblique fatigue crack tip in single-crystalline Fe-3.2 wt.% Si alloy is precisely observed by using cross-sectional transmission electron microscopy (TEM). The observation successfully reveals the existence of different dislocation structures (vein, ladder, labyrinth, cell) around the crack tip. The results clearly suggest that the crack growth is strongly related to the formation of dislocation cell structures. Additional fractographic observation suggests that the crack growth, the path of which is found to be the boundary between hard cell region and soft matrix, accompanies the formation of striation pattern along the boundary.

DOI： 10.1299/kikaia.76.251

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.4028/www.scientific.net/AMR.89-91.473

Language：English   Publishing type：Research paper (other academic)  

Crack tip dislocations and dislocations introduced by three point-bending tests at high temperature are observed by combinating scanning transmission electron microscopy and computed tomography (STEM-CT). Commercially available P type (001) single crystal silicon wafers were employed. A series of STEM image was acquired from -60 degrees to +60 degrees in tilt range with 2 degrees in tilt step. The diffraction vector was maintained close to g(hkl) = 220 during the acquisition by adjusting the [110] direction of the sample parallel to the tilt axis of the holder. Reconstructed images of dislocations revealed dislocation structures in three-dimension.

DOI： 10.4028/www.scientific.net/AMR.89-91.473

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.MAW200919

Other Link： http://dx.doi.org/10.2320/matertrans.MAW200919

Language：Japanese  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Fatigue crack propagation tests using a single-crystalline Fe-3.2 wt.%Si alloy are conducted for the purpose of investigating the effect of hydrogen gas on cyclic slip around the crack tip. The crack propagation rate is found to be larger in hydrogen gas than in non-hydrogen (helium) gas. The fracture surface and the near-tip cross-section of {110} crack are observed in detail by using a scanning electron microscope (SEM) and a transmission electron microscope (TEM), respectively. The observation reveals that, in helium atmosphere, the propagation is attributed solely to a ductile plastic rocess. In hydroen atmosphere, the propagation can be also attributed to a ductile plastic process except that the amount of plastic deformation is small and the cyclic slip is concentrated around the crack tip region. Different types of slip systems are found to be operative in helium and in hydrogen gas atmospheres, which is postulated to be correlated to the slip concentration and the increased propagation rate.

DOI： 10.1299/kikaia.75.1082

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.scriptamat.2009.03.020

Other Link： http://dx.doi.org/doi:10.1016/j.scriptamat.2009.03.020

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.scriptamat.2009.01.002

Other Link： http://dx.doi.org/10.1016/j.scriptamat.2009.01.002

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.MD200817

Other Link： http://dx.doi.org/10.2320/matertrans.MD200817

Language：Others  

Microscopic study on the effect of hydrogen on deformation process near stage II fatigue crack tip

Language：Others  

Microscopic study on the effect of hydrogen on fatigue crack growth process in a chromium-molybdenum steel

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)  

Brittle-ductile transition (BDT) behaviour was investigated in low carbon steel deformed by an accumulative roll-bonding (ARB) process. The temperature dependence of its fracture toughness was measured by conducting four-point bending tests at various temperatures and strain rates. The fracture toughness increased while the BDT temperature decreased in the specimens deformed by the ARB process. Arrhenius plots between the BDT temperatures and the strain rates indicated that the activation energy for the BDT did not change due to the deformation with the ARB process. It was deduced that the decrease in the BDT temperature by grain refining was not due to the increase in the dislocation mobility controlled by short-range obstacles. Molecular dynamics simulations revealed that moving dislocations were impinged against grain boundaries, creating a shielding field, and were reemitted from there with increasing strain. Grain refining led to an increase in the fracture toughness at low temperatures and a decrease in the BDT temperature. In the present paper, the roles of-rain boundaries have been discussed in order to explain the enhancement in the fracture toughness of fine-grained materials at low temperatures, and the decrease in the BDT temperature. [doi:10.2320/matertrans.MD200817]

DOI： 10.2320/matertrans.MD200817

Language：Others  

Microscopic study on the effect of hydrogen on deformation process near stage II fatigue crack tip

Language：Others  

Microscopic study on the effect of hydrogen on fatigue crack growth process in a chromium-molybdenum steel

Language：English   Publishing type：Research paper (other academic)  

Language：Others  

Three-Dimensional Observation of Dislocations by Electron Tomography in a Silicon Crystal (vol 49, pg 1953, 2008)

DOI： 10.2320/matertrans.E2008002

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.scriptamat.2008.06.042

Other Link： http://dx.doi.org/10.1016/j.scriptamat.2008.06.042

Language：English   Publishing type：Research paper (scientific journal)  

The fracture behaviour of single-crystal pure iron was studied by four-point bending of pre-cracked specimens at temperatures between 77 and 180 K and strain rates between 4.46 x 10(-5) and 4.46 x 10(-3) s(-1). Fracture behaviour changes from brittle to ductile with increasing temperature. The brittle-ductile transition (BDT) temperature increases with increasing strain rate. The relation between BDT temperature and strain rate follows an Arrhenius relation, giving an activation energy for the BDT of 0.33 eV. Dislocation-dynamics simulations of the crack-tip plasticity and resultant shielding of the crack tip were performed using two different variants of the dislocation velocity/stress/temperature relation. The models predict an explicit BDT, and give a good quantitative fit to the experimental transition temperatures. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actamat.2008.06.025

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.MAW200828

Other Link： http://dx.doi.org/10.2320/matertrans.MAW200828

Language：English   Publishing type：Research paper (scientific journal)  

Fracture toughness of polycrystalline Fe, Fe-3%Cr and Fe-9%Cr was measured by four-point bending of pre-cracked specimens at temperatures between 77 K and 150 K and strain rates between 4.46 x 10(-4) and 2.23 x 10(-2) s(-1). For all materials, fracture behaviour changed with increasing temperature from brittle to ductile at a distinct brittle-ductile transition temperature (T-c), which increased with increasing strain rate. At low strain rates, an Arrhenius relation was found between T-c and strain rate in each material. At high strain rates, T-c was at slightly higher values than those expected from extrapolation of the Arrhenius relation from lower strain rates. This shift of T-c was associated with twinning near the crack tip. For each material, use of an Arrhenius relation for tests at strain rates at which specimens showed twinning gave the same activation energy as for the low strain Fate tests. The values of activation energy for the brittle-ductile transition of polycrystalline Fe, Fe-3%Cr and Fe-9%Cr were found to be 0.21, 0.15 and 0.10eV, respectively, indicating that the activation energy for dislocation glide decreases with increasing chromium concentration in iron. (c) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2008.06.039

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English  

Other Link： http://dx.doi.org/10.1016/j.jnucmat.2008.06.039

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)  

Other Link： http://dx.doi.org/10.1016/j.msea.2006.12.174

Language：English   Publishing type：Research paper (scientific journal)  

With the aim of experimental clarification of the interaction between a crack and dislocations, crack-tip dislocations in two kinds of plastic zones in silicon crystals were directly observed by high-voltage electron microscopy to analyse by their detail characterisation. Three-dimensional analysis on crack-dislocation interaction revealed that they were shielding type dislocations in both 45 degrees-shear-type and hinge-type plastic zones, which accommodate mainly mode I stress intensity at the crack tip. The crack-tip shielding fields due to dislocations also have been visualised by photoelasticity. In specimens without pre-deformation, photoelastic images due to the mode I crack-tip field were observed when an external load was applied at room temperature. In specimens pre-deformed at high temperatures, photoelastic images corresponding to the dislocation shielding were observed. The shielding field has an effect of accommodating the tensile stress concentration due to the applied load, which increases the critical stress intensity factor for crack extension. (C) 2007 Published by Elsevier B.V.

DOI： 10.1016/j.msea.2006.12.174

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.ME200711

Other Link： http://dx.doi.org/10.2320/matertrans.ME200711

Language：Japanese  

Microscopic Approach for Fracture Toughness of Materials

DOI： 10.9773/sosei.49.19

Language：English   Publishing type：Research paper (other academic)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.jnucmat.2007.03.077

Other Link： http://dx.doi.org/10.1016/j.jnucmat.2007.03.077

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/0031-8949/2007/T128/017

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10704-006-0021-7

Other Link： http://dx.doi.org/10.1007/s10704-006-0021-7

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.msea.2005.02.084

Other Link： http://dx.doi.org/10.1016/j.msea.2005.02.084

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.msea.2004.05.058

Other Link： http://dx.doi.org/http://dx.doi.org/10.1016/j.msea.2004.05.058

Language：English   Publishing type：Research paper (scientific journal)  

In order to understand the dislocation process for the sharp brittle-to-ductile transition in silicon crystals, microstructures of plastic zones around crack tips have been investigated using high-voltage electron microscopy (HVEM) and atomic force microscopy (AFNI). Cracks were introduced into {110} silicon wafers at room temperature by Vickers indentation method. The temperature of specimens indented was raised to higher than 823K to activate dislocation sources around a crack tip under the presence of residual stress due to the indentation. The crack observed was extending along the <110> direction from the edge of the indent. AFNI study has revealed two types of fine slip bands around the crack tip: one type of slip bands is those parallel to <112>, and another type is those parallel to the <110> direction. The former is corresponding to so-called hinge-type plastic zone, and the latter is 45degrees-shear-type. HVEM study has revealed the characteristics of dislocation structures corresponding to the both types of plastic zones. Detailed analyses of each dislocation, including the determination of the sign of Burgers vector, have been made to characterize those plastic zones. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msea.2004.05.040

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1093/jmicro/dfh052

Other Link： http://dx.doi.org/10.1093/jmicro/dfh052

Language：Japanese  

Other Link： http://dx.doi.org/doi:10.2320/jinstmet.68.787

Language：English   Publishing type：Research paper (scientific journal)  

Fracture toughness of silicon crystals has been investigated using indentation methods and their surface energies have been calculated by molecular dynamics (MD). In order to determine the most preferable fracture plane at room temperature, a conical indenter was forced into a (001) silicon wafer at room temperature. Dominant {110} cracks were introduced from the indent, indicating that fracture occurs most easily along the {110} plane among the crystallographic planes of the <001> zone. To confirm this orientation dependence of fracture toughness, surface energies for those planes were computed using molecular dynamics. The surface energy calculated exhibits the minimum value of 1.50 J(.)m(-2) at the {100} plane and it increases up to 2.26 J(.)m(-2) at the {100} plane. Fracture toughness was derived from these computed surface energies, and it was shown that K-IC value for the {110} crack plane was the minimum among those for the planes of the <001> zone. Fracture toughness of {110} plane and the other planes of <001> zone were measured by the indentation fracture (IF) method. The result is qualitatively in a good agreement with those obtained from the MD, although the absolute KIC values estimated by the IF method were larger than those obtained by the calculation.

DOI： 10.2320/jinstmet.68.787

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1093/jmicro/dfh051

Other Link： http://dx.doi.org/10.1093/jmicro/dfh051

Language：English  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.44.681

Other Link： http://dx.doi.org/doi:10.2320/matertrans.44.681

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/01418610210141307

Other Link： http://dx.doi.org/10.1080/01418610210141307

Language：Japanese  

Dislocation Configurations near a Crack Tip and Its Infiuence on the Fracture Toughness in Silicon Crystals
Dislocations emitted from a crack tip in silicon single crystals have been investigated using a high voltage electron microscopy (HVEM). The influence of those crack tip dislocations on the fracture toughness has been discussed based on the 3-D stress analysis of crack-dislocation interaction. Pure screw dislocations were introduced not only ahead of a crack tip but also behind the tip. The dislocations ahead of the crack tip have the sign of Burgers vectors opposite to that of the dislocations behind the tip. These configurations of crack tip dislocations are understood by dislocation loop expansion from sources near the crack tip. The contribution to the fracture toughness by those crack tip dislocations was calculated, and it was found that 70&sim;90% increase in the fracture toughness was caused by a dislocation configuration corresponding to that observed in the early stage of dislocation emission from a crack tip.

DOI： 10.1299/kikaia.68.1505

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.43.2169

Other Link： http://dx.doi.org/10.2320/matertrans.43.2169

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.42.1839

Other Link： http://dx.doi.org/10.2320/matertrans.42.1839

Event date： 2024.9

Language：Japanese   Presentation type：Poster presentation  

Event date： 2024.9

Language：Japanese   Presentation type：Poster presentation  

Event date： 2024.9

Language：Japanese   Presentation type：Poster presentation  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2024.6

Language：Japanese   Presentation type：Poster presentation  

Venue：熊本県民交流パレア   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Poster presentation  

Venue：熊本県民交流パレア   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Poster presentation  

Venue：熊本県民交流パレア   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Poster presentation  

Venue：熊本県民交流パレア   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Poster presentation  

Venue：熊本県民交流パレア   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Poster presentation  

Venue：熊本県民交流パレア   Country：Japan  

Event date： 2022.3

Language：Others  

Country：Other  

Event date： 2022.3

Language：Others  

Country：Other  

Event date： 2022.3

researchmap

Event date： 2022.3

researchmap

Event date： 2021.9

Language：Others  

Country：Other  

Event date： 2021.9

researchmap

Event date： 2021.9

Language：Others  

Country：Other  

Event date： 2021.9

Language：Others  

Country：Other  

Event date： 2021.9

Language：Others  

Country：Other  

Event date： 2021.9

researchmap

Event date： 2021.9

researchmap

Event date： 2021.9

Language：Japanese   Presentation type：Poster presentation  

researchmap

Event date： 2021.9

Language：Others  

Country：Other  

Event date： 2021.9

Language：Others  

Country：Other  

Event date： 2021.6

Language：Others  

Country：Other  

Event date： 2021.6

Language：Others  

Country：Other  

Event date： 2019.9

Language：Japanese  

Venue：岡山大学   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山大学   Country：Japan  

Event date： 2019.9

Language：Japanese  

Venue：岡山大学   Country：Japan  

Event date： 2019.9

Language：Japanese  

Venue：岡山大学   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山大学   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山大学   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山大学   Country：Japan  

Event date： 2019.9

Language：Japanese  

Venue：岡山大学   Country：Japan  

Event date： 2019.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本県民交流パレア   Country：Japan  

Event date： 2019.6

Language：Japanese  

Venue：熊本県民交流パレア   Country：Japan  

Event date： 2019.6

Language：Japanese  

Venue：熊本県民交流パレア   Country：Japan  

Event date： 2019.6

Language：Japanese  

Venue：熊本県民交流パレア   Country：Japan  

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：島津製作所関西支社マルチホール   Country：Japan  

Event date： 2019.3

Language：Japanese  

Venue：東京電機大学   Country：Japan  

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京電機大学   Country：Japan  

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学   Country：Japan  

Event date： 2018.12

Language：Others  

Country：Other  

Event date： 2018.12

Language：Japanese  

Venue：熊本大学   Country：Japan  

Event date： 2018.10 - 2018.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Osaka International Convention Center   Country：Japan  

Event date： 2018.10 - 2018.11

Language：English  

Venue：Osaka International Convention Center   Country：Japan  

Event date： 2018.10 - 2018.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Osaka International Convention Center   Country：Japan  

Event date： 2018.10 - 2018.11

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2018.9

Language：Japanese  

Venue：仙台国際センター   Country：Japan  

Event date： 2018.9

Language：Japanese  

Venue：仙台国際センター   Country：Japan  

Event date： 2018.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台国際センター   Country：Japan  

Event date： 2018.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台国際センター   Country：Japan  

Event date： 2018.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台国際センター   Country：Japan  

Event date： 2018.9

Language：Japanese  

Venue：仙台国際センター   Country：Japan  

Event date： 2018.9

Language：Japanese  

Venue：仙台国際センター   Country：Japan  

Event date： 2018.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：関西大学千里山キャンパス   Country：Japan  

Event date： 2018.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Cité des Sciences et de l'Industrie   Country：France  

Event date： 2018.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Cité des Sciences et de l'Industrie   Country：France  

Event date： 2018.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Cité des Sciences et de l'Industrie   Country：France  

Event date： 2018.6

Language：Japanese  

Venue：北九州国際会議場   Country：Japan  

Event date： 2018.6

Language：Japanese  

Venue：北九州国際会議場   Country：Japan  

Event date： 2018.6

Language：Japanese  

Venue：北九州国際会議場   Country：Japan  

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2017.12

Language：English   Presentation type：Oral presentation (general)  

Venue：ニューウェルシティ宮崎   Country：Japan  

Event date： 2017.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海度大学   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：釧路工業高等専門学校   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学   Country：Japan  

Event date： 2017.9

Language：Japanese  

Venue：北海道大学   Country：Japan  

Event date： 2017.9

Language：Japanese  

Venue：北海道大学   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学   Country：Japan  

Event date： 2017.8 - 2017.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto University   Country：Japan  

Event date： 2017.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：山形大学   Country：Japan  

Event date： 2017.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：山形大学   Country：Japan  

Event date： 2017.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：山形大学   Country：Japan  

Event date： 2017.6

Language：Japanese  

Venue：熊本大学   Country：Japan  

Event date： 2017.6

Language：Japanese  

Venue：熊本大学   Country：Japan  

Event date： 2017.6

Language：Japanese  

Venue：熊本大学   Country：Japan  

Event date： 2017.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：首都大学東京   Country：Japan  

Event date： 2017.3

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：首都大学東京   Country：Japan  

Event date： 2017.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：首都大学東京   Country：Japan  

Event date： 2016.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：室蘭工業大学   Country：Japan  

Event date： 2016.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：苫小牧高専   Country：Japan  

Event date： 2016.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：大阪大学   Country：Japan  

Event date： 2016.9

Language：English   Presentation type：Oral presentation (general)  

Venue：大阪大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：大阪大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：大阪大学   Country：Japan  

Event date： 2016.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：大阪大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：大阪大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：大阪大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：大阪大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：大阪大学   Country：Japan  

Event date： 2016.7

Language：Japanese  

Venue：神戸製鋼所 長府製造所   Country：Japan  

Event date： 2016.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2016.6

Language：Japanese  

Venue：九州大学   Country：Japan  

Event date： 2016.6

Language：Japanese  

Venue：九州大学   Country：Japan  

Event date： 2016.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Ｒａｋｕｙｕ Kaikan   Country：Japan  

Event date： 2015.11

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2015.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Pacifico Yokoyama   Country：Japan  

Event date： 2015.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Warsaw University of Technology   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2015.9

Language：Japanese  

Venue：九州大学   Country：Japan  

Event date： 2015.9

Language：Japanese  

Venue：九州大学   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2015.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：フラクシア品川   Country：Japan  

Event date： 2015.8

Language：English  

Venue：Brno Convention and Enhibition Centre,   Country：Japan  

Brittle failure is one of the most catastrophic failure mechanisms operating in crystalline materials as it occurs very rapidly. While materials with a BCC structure or covalent bonding are especially susceptible, they typically fail in a brittle fashion only at low temperatures. Early investigations that sought to elucidate the mechanism behind this brittle to ductile transition, BDT, were performed using silicon single crystals as these can be grown dislocations free, the properties of dislocations in Si are well characterized, and the transition occurs over a narrow temperature window. One explanation for the transition is based on dislocation shielding, in which the stress field of the dislocations emitted from the crack accommodates the crack tip stress intensity. The amount accommodated is dependent not only on the Burgers vector of the emitted dislocations but also on the dislocation distribution around the crack tip. To discover the controlling mechanisms behind the BDT, knowledge of the three-dimensional spatial distribution of each type of dislocation is required.
A technique to visualize the spatial distribution of such dislocations is electron tomography. In order to acquire the images necessary for the reconstruction, the increased penetration power of a high-voltage electron microscope (HVEM) enables thicker samples to be viewed, which is useful for imaging at high tilt angles; in the case of silicon, the sample thickness can be several micrometres. In the present study, the Burgers vectors and spatial arrangement of the dislocations surrounding a crack tip in Si were characterized by combining HVEM-tomography with conventional g.b analysis. Using this information, the local stress intensity factor was calculated and a multiplication process for generating dislocation sources around a crack tip was proposed.
P-type (001) silicon wafers that are commercially available were used in this study.

Event date： 2015.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Rakuyu Kaikan, Kyoto University   Country：Japan  

Event date： 2015.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Rakuyu Kaikan, Kyoto University   Country：Japan  

Event date： 2015.6

Language：Japanese  

Venue：北九州国際会議場   Country：Japan  

Event date： 2015.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北九州国際会議場   Country：Japan  

Event date： 2015.6

Language：Japanese  

Venue：北九州国際会議場   Country：Japan  

Event date： 2015.5 - 2013.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Hilton Fukuoka Sea Hawk   Country：Japan  

Event date： 2015.3

Language：Japanese  

Venue：東京理科大学   Country：Japan  

Event date： 2015.3

Language：Japanese  

Venue：東京理科大学   Country：Japan