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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575
Publisher: The Iron and Steel Institute of Japan

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Tetsu-to-Hagané Advance Publication

Prediction Studies of Strip Centering with Flotation Dryer

Hirokazu Kobayashi, Yukio Takashima, Gentaro Takeda, Kenji Katoh, Tatsuro Wakimoto

Abstract

Flotation dryer systems are widely used to dry liquid layers on substrates such as films, paper and steel strips, and many reports discussing design optimization for better heat transfer characteristics and strip stability are available.

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Prediction Studies of Strip Centering with Flotation Dryer

Analysis of Pulse-to-Pulse Signal Uncertainty in LIBS Spectral Intensity on the Basis of Error Propagation

Tetsuo Sakka, Yoshihiro Deguchi

Abstract

Atomic spectral lines obtained by laser-induced breakdown spectroscopy (LIBS) often suffer from serious pulse-to-pulse fluctuation, which limits the accuracy of the quantitative analysis. Solving this problem is an important issue for improving the analytical performance of LIBS. In the present review the model to simulate the emission spectral intensity of LIBS measurements is introduced, and the method to evaluate the propagation of the pulse-to-pulse variation of plasma parameters to the variation of emission spectral intensity by the error propagation analysis is explained. The recent three studies found in the literature that investigated the pulse-to-pulse fluctuation of the spectral line intensities on the basis of error propagation analysis are reviewed.

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Analysis of Pulse-to-Pulse Signal Uncertainty in LIBS Spectral Intensity on the Basis of Error Propagation

Effect of Nb on Grain Growth Behavior in the Heat Affected Zone of Linepipe Steels

Daichi Izumi, Nobuyuki Ishikawa, Pello Uranga, Nerea Isasti, Jose Maria Rodriguez-ibabe, Douglas Stalheim, David Jarreta, David Martin

Abstract

Recrystallization and grain growth during plate rolling are prevented by Nb addition both with the solute drag and the Nb carbide precipitation. Although a fine microstructure is achieved in the base material, welding heat completely changes the microstructure in the heat affected zone (HAZ). In this study, laboratory simulation of the coarse grain HAZ (CGHAZ) thermal cycle of double submerged arc welded linepipe was carried out using low carbon steels containing different Nb contents. Extraction residue analysis of the simulated CGHAZ samples revealed that almost all the Nb remained in solid solution. To clarify the interaction of Nb carbide dissolution and grain growth on overall simulated HAZ microstructure evolution, additional weld HAZ thermal simulations were performed. It was found that Nb carbides remain undissolved at HAZ peak temperatures up to 1200℃ and showed significant pinning effect to prevent austenite grain growth. Significant grain growth was seen after continuous fast heating to 1350℃ peak temperature, while the higher Nb added steel showed a slower overall austenite grain growth rate, suggesting that grain growth in the HAZ at higher temperature was suppressed by the combined effects of slower coarse Nb carbide dissolution providing some pinning, and the solute drag effect of higher amounts of Nb in solid solution. A pronounced retardation of longer-term isothermal grain growth was identified at 1350℃ at higher levels of solute Nb, confirming the influence of Nb solute drag on high temperature resistance to austenite grain coarsening.

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Effect of Nb on Grain Growth Behavior in the Heat Affected Zone of Linepipe Steels

Effect of Inhomogeneous Microstructure on Strength and Fracture Resistance in Sharp Edge of Japanese Swords

Kwangsik Kwak, Takateru Yamamuro, Yoji Mine, Shigekazu Morito, Kazuki Takashima

Abstract

Microtensile and microfracture tests were performed on the sharp-edge regions of Japanese swords fabricated in the Muromachi and Showa periods, which are called old sword (OS) and modern sword (MS), respectively, to correlate the mechanical properties with the inhomogeneous microstructures. The hardness of the sharp-edge regions was characterised by the distribution of fine pearlite mixed in martensite microstructures. The OS containing a large fraction of fine pearlite exhibited a low hardness compared to the MS. Microtensile tests using sharp-edge specimens revealed a positive correlation between their tensile strength and strain-to-failure, as opposed to the common tendency in conventional carbon steels made by modern iron-making technology. The fracture surfaces of the sharp-edge specimens were composed of intergranular and dimple fracture features. The tensile strength and dimple fracture area fraction were higher in the OS than in the MS. These findings suggest that the fine pearlite microstructure contributes to increased strength in the sharp-edge region through inhibiting the linkage of intergranular cracking owing to local plastic deformation. Microfracture tests using the sharp-edge specimens revealed that the intrinsic fracture resistance of both OS and MS was determined by the intergranular fracture, whereas the fine pearlite microstructure increased the resistance to crack propagation. The micromechanical testing study indicates that in the sharp-edge regions, their strength and fracture toughness are simultaneously enhanced by the presence of fine pearlite although depending on its distribution.

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Effect of Inhomogeneous Microstructure on Strength and Fracture Resistance in Sharp Edge of Japanese Swords

Rupture of Thin Film of Surfactant Solution Due to Penetration of Spherical Particle

Kenji Katoh, Tatsuro Wakimoto

Abstract

We experimentally investigated the rupture conditions of a thin film of an aqueous surfactant solution when a spherical particle with a finite falling velocity penetrates the film. When the sphere passes through the film, the film wraps around the sphere, and a gas layer is maintained between the film and the spherical surface. When the velocity of the sphere is small, perforation occurs in the wrapping film below the equator of the sphere and the contact line moves along on the sphere surface. The energy instability occurs at a certain position of the contact line on the sphere surface, leading to rupture of the entire thin film. As the sphere velocity is increased, the perforation of the wrapping film occurs above the equator. In this condition, the probability of thin film rupture increases, since the perforation of the wrapping film immediately leads to rupture of the entire film. The motion of the gas between the thin film and the spherical surface was considered analytically from the balance between surface tension and viscous force. According to the result, the velocity condition above which the wrapping thin film could exist beyond the equator of the sphere was evaluated.

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Rupture of Thin Film of Surfactant Solution Due to Penetration of Spherical Particle

Effect of Hydrogen on Tensile Shear Strength of Spot-Welded Ultrahigh-Strength TRIP-Aided Martensitic Steel Sheet

Tomohiko Hojo, Akihiko Nagasaka, Ryusei Wakabayashi, Chihaya Tabata, Yota Kondo, Kazuma Ogasawara, Yuki Shibayama, Eiji Akiyama

Abstract

In this study, the effect of hydrogen on the tensile shear strength of spot-welded transformation-induced plasticity (TRIP)-aided martensitic (TM) steel sheet was investigated. The tensile shear tests were carried out on a tensile testing machine using the spot-welded specimen which was spot-welded at the lapped portion of 30 mm×30 mm using specimen with dimensions of width of 30 mm and length of 170 mm at crosshead speeds of v=0.5 to 100 mm/min with and without hydrogen. The results were summarized as follows.

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Effect of Hydrogen on Tensile Shear Strength of Spot-Welded Ultrahigh-Strength TRIP-Aided Martensitic Steel Sheet

Texture Development in Austenite during Tensile Deformation of 5%Mn Steel Accompanied by Deformation-Induced Martensite Transformation

Yusuke Onuki

Abstract

Medium manganese steels, containing 3~10 mass% of Mn, are considered promising as the 3rd generation high strength steel. In this study, in situ neutron diffraction experiments were conducted during uniaxial tensile deformation for Fe-4.91Mn-0.092C (mass%). The primary aim was to investigate the change of austenite texture accompanied with the deformation induced martensitic transformation (DIMT). It was observed that grains oriented <001> towards the tensile direction tend to persist during the deformation. Moreover, the fraction of <001> oriented grains increases due to crystal rotation caused by dislocation slip. Grains with <111> towards the tensile direction are consumed more rapidly than those with <001>. These observations are qualitatively reproduced by visco-plastic self-consistent model, additionally considering DIMT to ε martensite. Although ε martensite was not identified in the diffraction pattern obtained in this study, a previous microstructural study indicated the γεα’ type DIMT for the same material. In contrast, it is known that in low alloyed TRIP steels subjected to tensile deformation, grains with <111> tend to survive, where γα’ type DIMT occurs. Based on the results of this study, the orientation that persists after tensile deformation can distinguish between the DIMT mechanisms: γεα ’ or γα ’ type.

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Texture Development in Austenite during Tensile Deformation of 5%Mn Steel Accompanied by Deformation-Induced Martensite Transformation

Effects of Boron Addition on Low Cycle Bending Fatigue Strength of Gas Carburized Low Alloy Steel

Ai Goto, Masato Yuya, Kaori Kawano

Abstract

The effect of boron addition on low cycle bending fatigue strength of carburized steel was investigated. The low-cycle bending fatigue strength of B-added steel was improved compared to SCM420. When the fatigue failure was divided into the crack initiation process and the crack propagation process, the addition of boron did not affect the crack initiation life, but improved the crack propagation life. The presence of boron in B-added steels was evaluated using TOF-SIMS and AES measurements. Grain boundary segregation of boron was not observed in the gas carburized surface layer, but precipitation of BN was observed. On the other hand, grain boundary segregation of boron was observed from the carburized surface layer toward the 400 μm core side. Therefore, it is considered that the grain boundary strengthening effect of boron was not obtained in the carburized surface layer, and the crack initiation life did not change. 

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Effects of Boron Addition on Low Cycle Bending Fatigue Strength of Gas Carburized Low Alloy Steel

Evaluation of Fatigue Crack Initiation and Propagation Properties of Structural Steels with Different Cyclic Softening Behavior Based on Local Strain

Takayuki Yonezawa, Pengjun Luo, Seiichiro Tsutsumi

Abstract

In this paper, fatigue crack initiation and propagation properties of three structural steels with different static strength and cyclic softening behavior were evaluated and compared with the estimation results based on the local strain response. Steel C had the highest cyclic softening rate, which was 10 times that of steel A and twice that of steel B. The relationship between strain range and fatigue life in the fatigue life region shorter than 105 cycles was almost the same regardless of the test steels. The fatigue crack initiation life from the notch bottom of the SENT specimen was almost the same independent of static strength and cyclic softening rate. The crack initiation life estimated from the Strain range versus fatigue life equation using the local strain response measured by DIC was roughly in agreement with the experimental results. Steel C had the highest crack opening load and the slowest fatigue crack propagation rate compared to the other two steels. The local strain range at the fatigue crack tip showed a good correlation with the fatigue crack propagation rate irrespective of the steel grade. In addition, the estimates of fatigue crack propagation rate based on the local strain response were in almost agreement with the experimental results.

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Evaluation of Fatigue Crack Initiation and Propagation Properties of Structural Steels with Different Cyclic Softening Behavior Based on Local Strain

Measurement of Bubble Size Distribution and Generation Position of Bubbles Generated during Smelting Reduction of Iron Oxide-containing

Ko-ichiro Ohno, Taiga Eguchi, Tatsuya Kon

Abstract

Slag foaming is a phenomenon caused by the generation of CO bubbles due to the reaction between iron oxide in slag and carbon in pig iron. The purpose of this study is to explore the controlling factors of slag foaming by observing the bubble formation behavior caused by the chemical reaction between iron oxide and Fe-C alloy in slag. 0.06 g of Fe-C alloy was charged to the bottom of the BN crucible, and 6.0 g of slag (SiO2:CaO:Fe2O3 = 40:40:30) was charged on top of it. The crucible was placed in an infrared image heating furnace, and the temperature was rapidly raised to 1370°C at a rate of 1000°C/min in a N2 stream, then held for a predetermined time and rapidly cooled. After rapidly cooling, the internal structure of the sample was observed using a high-resolution X-ray CT device. The spherical equivalent volume is calculated based on the number of bubbles observed and their equivalent circle diameter, and the relationship between the volume ratio of small bubbles in the slag volume and the distance from the bottom of the crucible is calculated, and the bubble density and volume ratio are calculated. It was suggested that the value tends to increase as the distance from the bottom of the crucible increases.

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Measurement of Bubble Size Distribution and Generation Position of Bubbles Generated during Smelting Reduction of Iron Oxide-containing

Formation Mechanism of Joint Interface in Cold Spot Joining Method and its Joint Properties

Takumi Aibara, Masayoshi Kamai, Yoshiaki Morisada, Kohsaku Ushioda, Hidetoshi Fujii

Abstract

A novel solid-state joining method called Cold Spot Joining (CSJ) has been successfully developed. In this joining concept, the material near the joining interface is plastically deformed under high pressure to form a joining interface, resulting in the fragmentation of oxide films at the joining interface and the formation of strong interface. Medium carbon steel sheets were CS-joined under various process conditions. The joining temperature can be varied by the applied pressure during CSJ. Microstructural observations and hardness distribution indicated that the appropriate pressurization resulted in joining temperatures below the A1 point and suppressed the formation of the brittle martensitic structure. By providing appropriate applied pressure, sound S45C spot-welded joints were successfully produced, showing plug failure of the base metal in both tensile shear and cross-tension tests. Further investigation into the mechanism of interface formation reveals that the oxide film at the interface is fragmented and expelled. At the same time, dynamic recrystallization occurs at the interface and extremely fine new grains with dispersed fine cementite are formed at the interface to achieve the sound joining with sufficient strength.

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Formation Mechanism of Joint Interface in Cold Spot Joining Method and its Joint Properties

Dependence of Carbon and Nitrogen Content on Grain Refinement Strengthening in Austenitic Stainless Steel

Yoshihiro Oka, Ayumi Morimatsu, Takuro Masumura, Takahito Ohmura, Toshihiro Tsuchiyama

Abstract

The effects of C and N on solid solution strengthening and grain refinement strengthening were quantitatively evaluated using various austenitic stainless steels in which C and N were added independently to Fe-18 mass%Cr-12 mass%Ni alloys. As a result of evaluating the amount of solid solution strengthening from the intercept value in the Hall-Petch relationship, it was confirmed that N has a stronger solid solution strengthening capacity than C. On the other hand, the addition of C and N increased the slope of the Hall-Petch relationship, the so-called Hall-Petch coefficient, and the amount of grain refinement strengthening increased. Comparing the effects of C and N, there was no significant difference in the effect of increasing the Hall-Petch coefficient between the two elements at the same amount of addition. The critical grain boundary shear stress measured by nanoindentation tests and the Hall-Petch coefficient corresponded well for both steels, demonstrating that the increase in critical shear stress due to the addition of C and N results in increased grain refinement strengthening. However, the amount of grain boundary segregation was calculated to be considerably higher for C than for N, suggesting that N is more effective than C in increasing the critical grain boundary shear stress.

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Dependence of Carbon and Nitrogen Content on Grain Refinement Strengthening in Austenitic Stainless Steel

Stress and Plastic Strain Partitioning Behaviors and Those Contributions to Martensitic Transformation of Retained Austenite in Medium Manganese and Transformation-Induced Plasticity-Aided Bainitic Ferrite Steels

Tomohiko Hojo, Motomichi Koyama, Bakuya Kumai, Yutao Zhou, Yuki Shibayama, Ayumi Shiro, Takahisa Shobu, Hiroyuki Saitoh, Saya Ajito, Eiji Akiyama

Abstract

Stress and plastic strain distributions and those partitioning behaviors of ferrite and retained austenite were investigated in the medium manganese (Mn) and the transformation-induced plasticity-aided bainitic ferrite (TBF) steels, and the martensitic transformation behaviors of retained austenite during Lüders elongation and work hardening were analyzed using synchrotron X-ray diffraction at SPring-8. The stress and plastic strain of retained austenite and volume fraction of retained austenite were remarkably changed during Lüders deformation in the medium Mn steel, implying that the medium Mn steel possessed inhomogeneous deformation at the parallel part of the tensile specimen. On the other hand, the distributions of the stress, plastic strain and volume fraction of retained austenite were homogeneous and the homogeneous deformation occurred at the parallel part of the tensile specimen at the plastic deformation regime with work hardening in the medium Mn and TBF steels. The martensitic transformation of retained austenite at Lüders deformation in the medium Mn steel was possessed owing to the application of high stress and preferential deformation at retained austenite, resulting in a significant increase in the plastic deformation and reduction of stress in the retained austenite. The martensitic transformation of retained austenite at the plastic deformation regime with work hardening was induced by the high dislocation density and newly applied plastic deformation in retained austenite in the medium Mn steel whereas the TBF steel possessed gradual transformation of retained austenite which is applied high tensile stress and moderate plastic deformation.

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Stress and Plastic Strain Partitioning Behaviors and Those Contributions to Martensitic Transformation of Retained Austenite in Medium Manganese and Transformation-Induced Plasticity-Aided Bainitic Ferrite Steels

Hydrodynamic Behavior of Sphere Penetrating into Water Bath Covered with Oil Layer

Satoshi Hasui, Yoshihiko Higuchi

Abstract

To meet the increasing demand for low-impurity steel products, powder top blowing has been applied to the steelmaking process. Powder reagents penetrating deeper into the molten metal lead to longer resident time and higher efficiency of refining. Many studies have been performed on the basis of cold model experiments with a single liquid phase for clarifying the penetration behavior of the particle. However, the effects of the second liquid phase have been reported little whereas molten slag often exists on the surface of molten metal in the steelmaking process.

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Hydrodynamic Behavior of Sphere Penetrating into Water Bath Covered with Oil Layer

Multiscale Finite Element Analysis of Yield-point Phenomenon in Ferrite–Pearlite Duplex Steels

Shinnosuke Yanagawa, Ikumu Watanabe

Abstract

Yield-point phenomena in Ferrite–Pearlite duplex steels were investigated using multi-scale computational simulations. In this multi-scale simulations, stress–strain relationship of Ferrite phase was characterized by an elastoplastic constitutive model considering yield-drop behavior and its material constants were determined by minimizing residual error between a computational simulation and experiment of tensile test, where yield-point phenomenon in a tensile test of Ferrite steel was reproduced.

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Multiscale Finite Element Analysis of Yield-point Phenomenon in Ferrite–Pearlite Duplex Steels

Reverse Transformation Behavior in Multi-phased Medium Mn martensitic Steel Analyzed by In-situ Neutron Diffraction

Kyosuke Matsuda, Takuro Masumura, Toshihiro Tsuchiyama, Yusuke Onuki, Misa Takanashi, Takuya Maeda, Yuzo Kawamoto, Hiroyuki Shirahata, Ryuji Uemori

Abstract

The reverse transformation behavior during heating in Fe-10%Mn-0.1%C (mass%) martensitic alloy consisting of α’-martensite, ε-martensite and retained austenite was investigated using the in-situ neutron diffraction. When the temperature was elevated with a heating rate of 10 K/s, the ε→γ reverse transformation occurred first at the temperature range of 535–712 K, where Fe and Mn hardly diffused. In the temperature range where the ε→γ reverse transformation occurred, the full width at half maximum of the 200γ peak increased, indicating that the austenite reversed from ε-martensite contains high-density dislocations. In addition, the transformation temperature hardly depends on the heating rate and the crystal orientation of the reversed austenite was identical to that of the prior austenite (austenite memory), which suggests that the ε→γ reverse transformation would proceed through the displacive mechanism. After completion of the ε→γ transformation, the α’→γ reverse transformation occurred at the temperature range of 842–950 K. When the heating rate is low (<10 K/s), the reverse transformation start temperature significantly depends on the heating rate. It could be because the diffusional reverse transformation accompanying the repartitioning of Mn occurs. On the other hand, a higher heating rate (≥10 K/s) resulted in the disappearance of the heating rate dependence. This was probably due to the change in the transformation mechanism to the massive-type transformation, which is diffusional transformation without repartitioning of Mn.

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Reverse Transformation Behavior in Multi-phased Medium Mn martensitic Steel Analyzed by In-situ Neutron Diffraction

Dynamic Deformation Properties of Medium-Mn Multi-phase Steels Containing Retained Austenite

Yoshitaka Okitsu, Tomohiko Hojo, Satoshi Morooka, Goro Miyamoto

Abstract

We investigated the dynamic tensile properties of 4, 5, 6-mass%-Mn-containing low carbon steels with multi-phase microstructures containing retained austenite. The five materials used were classified into two groups. The first group of materials, with around 10% of retained austenite, showed normal strain rete dependence of yield strength (YS) and tensile strength (TS) as in conventional high strength steels. The second group of materials, containing 25-36 % of retained austenite and exhibiting Lüders elongation, showed also normal strain rate dependence of YS and flow stress at Lüders deformation, but TS varied in a complex manner. Among the second group, in the 4 Mn steel, TS was nearly constant at strain rates below 1 s-1 and increased slightly at higher strain rates. In the 5 and 6 Mn steels, TS once decreased up to the strain rate of 1 or 10 s-1, and then began to increase at higher strain rates. These behaviors were discussed in terms of temperature rise during plastic deformation and thermal stability of retained austenite. In the 4 Mn steel with relatively unstable retained austenite, almost all the austenite transforms regardless of strain rate. In the 5 and 6 Mn steels, where the retained austenite is moderately stable, its martensitic transformation is suppressed due to temperature rise, resulting in the decrease in TS at relatively low strain rates. At higher strain rates, the increase in flow stress prevails and TS begins to increase.

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Dynamic Deformation Properties of Medium-Mn Multi-phase Steels Containing Retained Austenite

Effect of Local Deformation Microstructure on Ductile Fracture Behavior of Ferrite-Bainite Duplex Steel

Kyono Yasuda, Nobuyuki Ishikawa, Jin Sueyoshi, Tatsuya Morikawa, Masaki Tanaka, Kenji Higashida

Abstract

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.

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Effect of Local Deformation Microstructure on Ductile Fracture Behavior of Ferrite-Bainite Duplex Steel

Role of Retained Austenite and Deformation Induced Martensite in 0.15C-5Mn Steel Monitored by in-situ Neutron Diffraction Measurement during Tensile Deformation

Takayuki Yamashita, Satoshi Morooka, Wu Gong, Takuro Kawasaki, Stefanus Harjo, Tomohiko Hojo, Yoshitaka Okitsu, Hidetoshi Fujii

Abstract

A Fe-0.15C-5Mn-0.5Si-0.05Nb medium Mn steel annealed at 660℃ and 685℃ both exhibited inhomogeneous deformation with Lüders deformation and extremely high work hardening rates, but with different Lüders strain and work hardening behavior. In-situ neutron diffraction measurements during tensile test were performed to investigate changes in the phase stresses and in the contributed stresses to the strength of the constituent phases, and crystal orientation of austenite. The role of each constituent phase in the deformation and the effect of crystallographic orientation on austenite stability were discussed. Deformation induced martensite showed excellent phase stress and contributed to the strength approximately 1000 MPa, which is close to macroscopic tensile strength. Although austenite contributed less to the strength, but during Lüders deformation and work hardening stage, it continuously transformed to martensite as the deformation progressed, suggesting that it mainly contributed to the ductility of the steels through a transformation induced plasticity effect. Austenite transformed to martensite in all crystallographic orientations during Lüders deformation, but there was a tendency for more <311> austenite grains parallel to the tensile direction to remain.

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Role of Retained Austenite and Deformation Induced Martensite in 0.15C-5Mn Steel Monitored by in-situ Neutron Diffraction Measurement during Tensile Deformation

Microstructure and Plasticity Evolution During Lüders Deformation in an Fe-5Mn-0.1C Medium-Mn Steel

Motomichi Koyama, Takayuki Yamashita, Satoshi Morooka, Takahiro Sawaguchi, Zhipeng Yang, Tomohiko Hojo, Takuro Kawasaki, Stefanus Harjo

Abstract

The local plasticity and associated microstructure evolution in Fe-5Mn-0.1C medium-Mn steel (wt.%) were investigated in this study. Specifically, the micro-deformation mechanism during Lüders banding was characterized based on multi-scale electron backscatter diffraction measurements and electron channeling contrast imaging. Similar to other medium-Mn steels, the Fe-5Mn-0.1C steel showed discontinuous macroscopic deformation, preferential plastic deformation in austenite, and deformation-induced martensitic transformation during Lüders deformation. Hexagonal close-packed martensite was also observed as an intermediate phase. Furthermore, an in-situ neutron diffraction experiment revealed that the pre-existing body-centered cubic phase, which was mainly ferrite, was a minor deformation path, although ferrite was the major constituent phase.

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Microstructure and Plasticity Evolution During Lüders Deformation in an Fe-5Mn-0.1C Medium-Mn Steel

Quantitative Evaluation of the Relationship between Strain and Color Change in Opal Photonic Crystal Films and Application into Complex Specimen Geometries

Yutao Zhou, Zhipeng Yang, Motomichi Koyama, Saya Ajito, Tomohiko Hojo, Hiroshi Fudouzi, Eiji Akiyama

Abstract

The color change of opal photonic crystal films (OPCFs) due to deformation was quantitatively evaluated using digital image correlation (DIC) analysis. OPCFs were pasted on specimens of three different gauge geometries, and random patterns were formed on the opposite side of each specimen for DIC analysis. To assess the applicability of using OPCFs-based strain characterization for analyzing steel structural components and associated metallurgical analyses, smooth, width-gradient, and holed specimens were prepared in this study. As deformation increased in the smooth specimen, the color of the OPCFs changed significantly. The color change in the OPCFs could be quantitatively converted into strain values through Hue value analysis. Heterogeneous strain distributions could also be quantitatively analyzed using OPCFs-based analysis at the submillimeter or millimeter scale. When the strain gradient is too high, for example, near a stress concentration site such as a hole, local peeling of the OPCFs away from the specimen surface can occur. Consequently, for quantitative characterization, we must take proper care when measuring this upper limit of the “strain gradient” as well as strain, which would depend on the adhesion and surface condition of the specimen.

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Quantitative Evaluation of the Relationship between Strain and Color Change in Opal Photonic Crystal Films and Application into Complex Specimen Geometries

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