Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/09507116.2023.2203966

researchmap

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2207/qjjws.40.266

researchmap

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

researchmap

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

researchmap

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

researchmap

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

researchmap

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

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Trans Tech Publications, Ltd.  

It is widely accepted that the dominant deformation mechanism of fine-grained superplasticity is through grain boundary sliding (GBS) that occurs in fine-grained materials. However, it has been reported that in “Class I” solid solution alloys, superplastic-like behavior controlled by trans-granular deformation occurs by solute drag creep. In this study, we have investigated superplastic behavior in a fine-grained aluminum solid solution alloy with a thermally unstable microstructure. To obtain fine-grained microstructure, friction stir processing (FSP) was applied to a commercial 5083 aluminum (Al−Mg) alloy. An equiaxial fine-grained microstructure with a grain size of 7.4 μm was obtained after FSP; however, this microstructure was unstable at high temperatures. Generally, for fine-grained superplasticity or GBS to occur or continue, the fine-grained microstructure must be smaller than 10 μm during high-temperature deformation. However, a large elongation of over 200% was observed at high temperatures despite the occurrence of grain growth. From microstructural observations, it was determined that a fine-grained microstructure is maintained in the early stage of deformation, but at strain levels greater than 100%, trans-granular deformation occurs. The microstructural feature of this trans-granular deformation is similar to the deformation microstructure of solute drag creep observed in “Class I” solid solution alloys. This indicates that a change in the deformation mechanism from GBS to solute drag creep takes place during high-temperature deformation. Here, based on our observations on our model system, which is a thermally unstable aluminum solid solution alloy, we discuss the possibility of a superplastic elongation occurring by means of a transition of the deformation mechanism.

DOI： 10.4028/www.scientific.net/MSF.941.1216

researchmap

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

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Society of Materials Science Japan  

The stress–strain relationship and microstructural evolution of a fine-grained 5083 aluminum alloy produced via friction-stir processing (FSP) during high-temperature tensile deformation were investigated. The FSP of the 5083 aluminum alloy resulted in the formation of a homogeneous fine-grained microstructure. Based on the stress–strain relationship, it was found that the 5083 aluminum alloy exhibited a large elongation, especially at a temperature above 693 K. The stress exponent and the activation energy for deformation, which were determined by the flow stress at a nominal strain of 0.03, were approximately 2.5 and 123 kJ/mol, respectively. These results suggest that grain boundary sliding accommodated by the solute drag motion of dislocations was the rate-controlling process in the early stages of deformation. The largest elongation of 350% occurred at 743 K and an initial strain rate of 1.0 10−3 s−1. In this case, the grain aspect ratio increased with increasing nominal strain, which indicated that equiaxed grains continuously elongated along the tensile axis during high-temperature deformation because of dislocation creep. The value of the stress exponent increased with increasing strain. From our experimental results, the dominant deformation mechanism was determined to change during the tensile test, and the contribution of dislocation creep to the high-temperature deformation increased as the deformation proceeded.

DOI： 10.2472/jsms.67.568

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

In this study, the superplastic behavior on a fine-grained aluminum solid solution alloy consisting of thermally unstable microstructures was investigated. In order to obtain the fine-grained microstructure, friction stir processing (FSP) was applied to a commercial 5083 aluminum alloy. An equiaxial fine-grained microstructure of 7.8 ìm was obtained after FSP, but this microstructure was thermally unstable at high temperatures. Commonly, for fine-grained superplasticity to occur (or to continue grain boundary sliding (GBS)), it is necessary to keep the fine-grained microstructure to less than 10 ìm during the high-temperature deformation. However, in this study, a large elongation of over 200% was observed at high temperatures in spite of the occurrence of grain growth. From the microstructural observations, it was determined that the fine-grained microstructure was maintained until the early stage of deformation, but the transgranular deformation was observed at a strain of over 100%. The microstructural feature of the abovementioned transgranular deformation is similar to the deformation microstructure of the solute drag creep occurring in "Class I"-type solid solution alloys. This indicates that the deformation mechanism transition from GBS to the solute drag creep occurred during high-temperature deformation. Here, the possibility of occurrence of the superplastic elongation through deformation mechanism transition is discussed as a model of the thermally unstable aluminum solid solution alloy.

DOI： 10.4028/www.scientific.net/KEM.723.21

Scopus

researchmap

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

<p>This work investigated the microstructural evolution occurring during high-temperature tensile tests (743 K, strain rate 1×10⁻³ s⁻¹) of a friction stir processed polycrystalline solid solution 5083 aluminum alloy, along with the effect of the microstructure change on the room-temperature mechanical properties. Grain refinement was effectively achieved in the stir zone, with the mean observed grain size less than 10 µm. The nominal stress–nominal strain curve indicated that the flow stress drastically increased until a maximum stress value at which point fracture occurred. The value of elongation to failure exceeded 300%; this high ductility can be referred to as superplastic-like elongation. The area fraction of cavity increased with increasing strain. Room-temperature tensile tests at a strain rate of 1×10⁻³ s⁻¹ revealed that the strength and ductility decreased with an increasing area fraction of cavity, and that the extent to which the strength and ductility are affected depends on the cavity.</p>

DOI： 10.2464/jilm.67.361

CiNii Books

researchmap

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

DOI： 10.2320/materia.56.346

CiNii Books

researchmap

Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：The Japan Society of Mechanical Engineers  

<p>This paper discusses large superplastic-like elongation through a deformation mechanism transition in fine-grained Al−Mg alloys. To obtain a fine-grained microstructure, we adapted friction stir processing (FSP) for use in Al−Mg alloys. The average grain size after FSP in this study was approximately 7 μm. However, this microstructure was thermally unstable, and grain growth easily occurred above 773 K. High-temperature tensile testing showed large elongation of over 200 % over a wide range of high-temperature tensile conditions. In the initial deformation stage at a strain of 0.1, the dominant deformation mechanism in this alloy, from the viewpoint of the stress exponent and activation energy for deformation, was considered to be grain boundary sliding (GBS) rate-controlled by the interdiffusion of Mg in Al. However, the deformed microstructures were equiaxial until a strain of 0.5, while above a strain of 0.5 they were elongated in the tensile axis direction. This feature of elongation of the microstructure is similar to solute-drag creep deformation. Solute-drag creep is known as one of the deformation mechanisms that exhibit superplastic-like behavior in Class I solid solutions. Moreover, Al−Mg alloys are widely known as typical Class I solid solutions. These microstructural changes were discussed by constructing a deformation mechanism map. From this, it was considered that grain growth during high-temperature deformation resulted in transition of the deformation mechanism from GBS to solute-drag creep.</p>

DOI： 10.1299/jsmemecj.2017.S0410202

researchmap

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

researchmap

Language：English  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

Class-I or Class-A solid solutions are substitutional with a relatively large difference in size between the solute and solvent atoms. High-temperature deformation of these solid solutions causes uniform transgranular deformation because of the solute drag motion of dislocations. Consequently, enhanced ductility can be obtained regardless of grain size. In our research, we specifically investigated the effects of second-phase particles resulting from adding impurity atoms on the hot ductility
i.e., how the second-phase particles obstruct the solute drag motion of dislocations. In this study, the effect of Mn and Cr impurities on the high-temperature ductility of typical Class-I Al−Mg solid solutions is investigated. The results show that hot ductility in the basic Al−Mg alloy leads to an elongation to fracture of above 200% at 673 and 723 K. We found that the dominant deformation mechanism causing high ductility is solute drag creep. The hot ductility decreases when Cr is added to the basic alloy, but an elongation to fracture of above 200% can still be achieved by adding Mn, although the elongation is less than that of the basic alloy.

DOI： 10.4028/www.scientific.net/MSF.838-839.249

Scopus

researchmap

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

researchmap

Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmemp.2015.23._105-1_

CiNii Books

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Society of Materials Science, Japan  

The effect of Al content on the fracture-behavior transition from brittle to ductile fracture due to strain-rate changes in various Fe-Si-Al (Si + Al = 4 wt%) alloys was studied. The fracture-behavior transition was investigated using tensile tests at a wide range of strain rates ranging from 10^-3 to 10³ s^-1. For Fe-Si-Al alloys with low Al content, the tensile sample fractured in a brittle manner at high-strain rates. On the other hand, at low-strain rates, nominal stress-plastic strain curves represented both uniform and local elongations, and the specimen fractured in a ductile manner. The fracture-behavior transition due to strain-rate changes was observed in Fe-Si-Al alloys. The strain rate at which the fracture-behavior transition occurred in Fe-Si-Al alloys increased with increasing Al content, and the brittle fracture of Fe-Si (high Fe content) alloys could be successfully suppressed in the presence of Al.

DOI： 10.2472/jsms.64.725

CiNii Books

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

In this study, the effects of temperature and strain rate on the deformation twinning behavior in Fe-5%Si alloy were investigated. Tensile tests at various temperatures (198-248 K) and strain rates (0.1-0.01 s(-1)) were carried out up to a strain of 0.8%. The presence of deformation twins was confirmed in all the tensiled specimens. The results of crystal orientation analysis by SEM-EBSP indicated that the (112) plane is the twinning plane for the twins formed in the grains. The area fraction and the width of deformation twin increased with decreasing temperature or with increasing strain rate. This tendency can be explained by the relationship between the resolved shear stress and the dislocation velocity.

DOI： 10.2355/tetsutohagane.101.46

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

In this study, the effects of temperature and strain rate on the deformation twinning behavior in Fe-5%Si alloy were investigated. Tensile tests at various temperatures (198-248 K) and strain rates (0.1-0.01 s(-1)) were carried out up to a strain of 0.8%. The presence of deformation twins was confirmed in all the tensiled specimens. The results of crystal orientation analysis by SEM-EBSP indicated that the {112} plane is the twinning plane for the twins formed in the grains. The area fraction and the width of deformation twin increased with decreasing temperature or with increasing strain rate. This tendency can be explained by the relationship between the resolved shear stress and the dislocation velocity.

DOI： 10.2355/isijinternational.55.1496

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Journal of the Japan Society of Powder and Powder Metallurgy  

It may be important to elucidate the mechanism of grain growth during the early stage of sintering, especially for micro-scale sintered products, of which size is close to that of powder particles. This study aims to clarify the grain growth behavior in powder compacts, that is, porous bodies. Sintering experiments of the powder compacts with poly crystalline nickel particles were conducted in temperatures lower than usual, for long time, and the change in crystal grain size were revealed by electron backscatter diffraction analysis in a scanning electron microscope. It was found that the crystal grain size increased, but did not go over the size of powder particles in the case of sintering at the lower temperatures. A phase-filed simulation of sintering process for two polycrystalline particles was also performed to examine the effects of neck growth on grain boundary migration. It was confirmed that the two polycrystalline particles of equal-size became two single-crystal grains when the sintering shrinkage rate was set to be low, which may be correspond to the experimental results at the lower temperatures.

DOI： 10.2497/jjspm.61.473

Scopus

researchmap

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

DOI： 10.4028/www.scientific.net/MSF.783-786.910

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Society of Materials Science Japan  

Fracture behavior transition due to strain rate change in Fe-5%Si alloy with dislocation microstructures was studied to investigate the effect of pre-deformation on toughness. The Fe-5%Si alloy was multi-passed rolled (pre-deformed) at 1073K to various reductions up to 50% to introduce dislocation microstructure. The room temperature tensile deformation was conducted at various strain rates from 10-5 to 100/s. Electron backscattering diffraction measurements clarified that the dislocations were successfully introduced within the grains. All rolled alloys were fractured with local elongation (necking) at slower strain rate. When strain rate was faster, the local elongation disappeared and the fracture manner was turned to brittle. The strain rate at which fracture behavior changed increased with increasing of the reduction. On the other hand, the almost fully recrystallized Si steel was fractured in the brittle manner at any strain rate and the transition strain rate was not found. The fractured tensile specimen with no local elongations contains deformation twins
however, these deformation twins were not observed in the fractured specimen with local elongations. This result indicates that the dislocation structure evolved during rolling suppressed the twinning and that the dislocation structure is effective for the enhancement of both ductility and toughness in Fe-5%Si alloy. © 2014 The Society of Materials Science, Japan.

DOI： 10.2472/jsms.63.467

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications  

In this study, the high-temperature ductility of a fine-grained, polycrystalline 5083 solid solution alloy was investigated. The composition of the alloy in mass% was Al-4.5 Mg-0.68 Mn-0.19 Fe-0.13 Si-0.11 Cr. Grain refinement was effectively achieved in the stir zone by a friction stir process, and the grain size could be reduced to 3.7 μm. Tensile tests were performed at temperatures ranging from 643 to 743 K and strain rates ranging from 0.001 to 0.1 /s. The stress-strain curves showed that the flow stress continuously decreased until it reached a maximum value of stress and fractured after the initial strain hardening occurred. The value of elongation-to-failure was more than 100% when temperatures were greater than 693 K. The high ductility observed at this point can be referred to as superplastic-like elongation. This phenomenon has been reported in some Al-Mg alloys. The experimentally determined stress exponent (n value) and activation energy for deformation were about 2.5 and 123 kJ/mol, respectively. These results suggest that the grain boundary sliding, accompanied by solute drag motion of dislocations, was a rate controlling process for deformation. © (2014) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/AMR.922.360

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The dependence of the e martensite transformation on the crystallographic orientation during a tensile test of metastable high-manganese austenitic steel, Fe-30 mass% Mn, with a polycrystalline microstructure was studied. The epsilon martensite plates were formed after the steel yielded by slipping, and the volume fraction of the epsilon martensite increased with increasing strain. No significant orientation dependence of the martensite formation was observed in the early stage of the tensile deformation, but when the sample was further strained up to about 30%, the tensile directions of the grains with martensite were preferentially found to be nearly parallel to the &lt; 111 &gt; direction of the austenite matrix. This orientation dependence corresponded with the orientation preferable for the development of local misorientations as detected by EBSD. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msea.2013.03.071

Web of Science

researchmap

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

researchmap

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

The influence of the microstructure on the tensile properties and fracture behavior of Hadfield steel at high strain rate were studied. Hadfield steel samples with different mean grain sizes and carbon phases were prepared by rolling at medium temperatures and subsequent annealing. A sample with an average grain size larger than 10 mu m, and a small number of carbides shows ductility with local elongation (post uniform elongation) at a high-speed tensile deformation rate of 10(3) s(-1). In addition, the fracture surface changes from brittle to ductile with increasing strain rate. In contrast, a fine-grained sample with carbides undergoes brittle fracture at any strain rate. The grain size dependence is discussed by considering the dynamic strain aging as well as the emission of dislocation from cracks. The accelerated diffusion of carbon due to grain refinement is considered as one of the important reason for brittle fracture in the fine-grained Hadfield steel.

DOI： 10.1007/s10853-012-6604-y

Web of Science

researchmap

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

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

The fracture behavior transition due to the change of strain rate in 5%Si magnetic steel with dislocation microstructures was studied. The Si steel was multi-passed rolled at 800 degrees C to a various reductions up to 50%. The room temperature tensile deformation was conducted at various strain rates from 10(-5)/s to 10(0)/s. All rolled steels were fractured in ductile manners with local elongation (necking) at slower strain rate. When strain rate was faster, the local elongation disappeared and the fracture manner was turned to brittle. The strain rate at which fracture mechanism changed from ductile to brittle increased with the increasing of the reduction. On the other hand, the almost fully recrystallized Si steel was fractured in the brittle manner at any strain rate and the transition strain rate was not found. The fractured tensile specimen with no local elongations contains deformation twins; whereas these deformation twins were not observed in the fractured specimen with local elongations. This result indicates that dislocation structure evolved during rolling suppressed the twinning and that the dislocation structure is effective for the enhancement of toughness in Si steel.

DOI： 10.4028/www.scientific.net/MSF.706-709.2187

Web of Science

researchmap

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

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

In order to investigate the effect of strain rate on TRIP effect in metastable austenitic steels, tensile deformation behavior of JIS-SUS301L steel was examined at wide range of strain rates between 1(10(3)/s and 10(-1)/s, in addition of the comparison with data of stable austemtic steel (JIS-SUS3 10S). Concerning of the SUS3011. steel. the 0.2% proof stress increased and the uniform elongation decreased with increasing of strain rate. The tensile strength decreased with an increase in strain rate between 10-3/s and 101/s and then increased again at strain rate more than IO'Is. The significant difference between the strain rate dependences on tensile strength and uniform elongation of SUS30IL, and SUS310S was clarified especially at strain rates between 10(-3)/s and 10(1)/s. As far as the effect of strain rate on stress-induced martensitic transformation behaviors is concerned, the volume fraction of stress-induced martensite at the same inle strain decreased with increasing of strain rate. I hese stress-induced transformation behaviors were associated with the tensile strength and uniform elongation of SUS301 L steel between 10(3)/s and 10(11/s). The conditions of stress-induced martensitic transformation in order to obtain better uniform elongation at a high strain rate of 10% were discussed by the calculations USITH2 the Weng secant method.

DOI： 10.2355/tetsutohagane.97.450

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

We investigated the oxidation behavior and the effect of the amount of SiC added on oxidation resistance in both hot-pressed ZrB2-MoSi2-SiC composites, 55ZrB(2)-40MoSi(2)-5SiC and 40ZrB(2)-40MoSi(2)-20SiC (vol.%), exposed to dry air at 1500 degrees C for up to 10 h. Quantitative electron microprobe analysis characterizations of the chemical compounds of post-oxidized composites were carried out. Parabolic oxidation behavior was observed for both composites. The addition of SiC improved the oxidation resistance of ZrB2-MoSi2-SiC composites, and the improvement enhanced with amount of SiC added. The microstructure of the post-oxidized composites consisted of two characteristic regions: oxidized reactive region and unreactive bulk material region. The oxidized reactive region divided into an outermost dense silica-rich scale layer and oxidized reactive mixture layer. The improvement of oxidation resistance with SiC addition is associated with the presence of a thicker dense outermost scale layer which inhibited inward diffusion of oxygen through it. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

DOI： 10.1016/j.ceramint.2010.09.034

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Microstructures of ZrB2 ceramics consolidated by hot-pressing and spark plasma sintering were investigated by transmission electron microscopy (TEM), combining energy dispersive X-ray spectroscopy (EDX). The microstructures of both ceramics were compared. Amount of impurities was lower for ZrB2 consolidated by spark plasma sintering than for hot-pressed ZrB2. In particular, oxygen impurity was not detected even at the grain-boundaries in ZrB2 consolidated by spark plasma sintering. The cleaning effect generated on the powder surfaces during spark plasma sintering cycle was displayed. In addition, dislocations were present only in the spark plasma sintered ZrB2 ceramic, as a result of localized high stresses. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

DOI： 10.1016/j.ceramint.2009.10.025

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Fracture behaviour transitions due to change in the strain rate in steels with various Si content ranging from 2% to 5 wt% were studied. Room-temperature tensile tests were conducted over wide range of strain rates ranging from 10(-3)s(-1) to 10(-3)s(-1). Concerning of the steels with low Si content (no more than 3%), the nominal stress - nominal strain curves represented both uniform and local elongations at all strain rates. On the other hand, in 4% Si steel at a strain rate higher than 10(1)s(-1) the tensile sample broke down without local elongation (necking). The stress at breaking was found to be nearly equal to its work hardening rate. The strain rate at which fracture behaviour transition took place in 5% Si steel (10(-1)s(-1)) was lower than that in 4% Si steel. TEM observations clarified the existence of deformation twins in the sample that fractured without necking. These results indicated that Si addition is subject to the brittle fractures and that the fracture mechanism transition is closely related with the deformation twinning behaviour.

DOI： 10.4028/www.scientific.net/MSF.654-656.1303

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER/PLENUM PUBLISHERS  

This study reports the oxidation behavior of hot-pressed ZrB2 ceramics, with 10, 20 and 40 vol.% MoSi2 additives, exposed to dry air at 1500 A degrees C for up to 10 h. The effect of the amount added MoSi2 on oxidation resistance was assessed. Quantitative electron microprobe characterizations of the oxidized ZrB2 with MoSi2 additives were carried out with electron probe micro analysis. Parabolic oxidation behavior was observed for the three compositions. The oxidation resistance was significantly improved with MoSi2 additives. Reaction-product phase compositions and phase distribution were thoroughly characterized from the oxidized surface through to the unreactive bulk material. It was found that the oxidation products consisted of nonstoichiometric amorphous SiO2, stoichiometric crystalline ZrO2, and MoB. The amounts of these phases in the oxidized reactive region were qualitatively determined.

DOI： 10.1007/s11085-009-9165-y

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：VERLAG STAHLEISEN MBH  

The hot deformation behaviour of a 0.47%C (JIS-S45C) steel in the stable austenite region was systematically investigated under various deformation conditions to collect fundamental data on its high-temperature deformation and microstructure evolution. The medium carbon steel showed dynamic recrystallization in a wide range of temperatures (850 degrees C similar to 1150 degrees C) and strain rates (10(-3) s(-1)similar to 10(0) s(-1)) in the stable austenite region. The dynamically recrystallized grain size was monotonically decreasing with increasing steady state stress. The minimum grain size obtained through dynamic recrystallization was 8.3 mu m when the S45C specimen was deformed at 850 degrees C and 1 s(-1). The stress-strain relationships were formularized based on a phenomenological model. The stress-strain curves estimated by the obtained equation were in good agreement with the experimental results.

DOI： 10.2374/SRI09SP049

Web of Science

researchmap

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

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Microstructure of the hot-pressed ZrB2 with MoSi2 additive was investigated by transmission electron microscopy (TEM). The effect of MoSi2 addition on the microstructure of the ceramic was assessed. For the pure ZrB2, the microstructure consisted of the equiaxed ZrB2 grains and a few elongated ZrB2 grains. For the ZrB2 with MoSi2 additive, the microstructure consisted almost entirely of equiaxed ZrB2 grains. A few dislocations were present in the ZrB2 grains. In addition, high-resolution TEM observations showed that the intergranular amorphous phase was absent at two ZrB2 grain boundaries in the ZrB2 with MoSi2 additive.

DOI： 10.1111/j.1551-2916.2009.03040.x

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The elastic moduli, hardness, fracture toughness, and flexural strength of a hot-pressed ZrB2-MoSi2-SiC composite were examined. The effects of MoSi2 and SiC contents were assessed. The dense compacts of ZrB2-MOSi2-SiC were produced by hot-pressing at 1800 degrees C for 30 min under a pressure of 30 MPa in vacuum. Ten series compositions of ZrB2-MoSi2-SiC, with the range from 10 to 40 vol.% for MoSi2 and 5 to 20 vol.% for SiC, were studied. The shear modulus of ZrB2-MoSi2-SiC was in the range of 190-216 GPa, and Young's modulus measured was in the range of 438-490 GPa. The ranges of hardness and fracture toughness values were measured to be 13.2-16.8 GPa, and 2.6-3.7 MPa m(1/2), respectively. The average flexural strength of ZrB2-MoSi2-SiC ranged from 369 to 863 MPa, depending on MoSi2 and SiC contents. The highest strength was obtained for 5 vol.% SiC-containing ZrB2-MoSi2-SiC, having the value of 863 MPa. (C) 2008 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jeurceramsoc.2008.01.003

Web of Science

researchmap

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

DOI： 10.2320/materia.44.971

CiNii Books

researchmap

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

In this study, the energy and atomic structure of the 〈110〉 symmetric tilt boundaries in palladium were calculated using a molecular dynamics (MD) method and the electronic structures of hydrogen in the bulk and at the grain boundaries were calculated using discrete-variational Xα (DV-Xα) molecular orbital cluster calculaion by solving Hartree-Fock-Slater equation. The result of MD simulation revealed that the energy of the 〈110〉 symmetric tilt boundary of palladium depended on the misorientation angle and that there were large energy cusps at the misorientation angles which correspond to the {111}∑3 and {113} ∑11 symmetric tilt boundaries. The atomic structure of all 〈110〉 symmetric tilt boundaries could consist of the combination of the {331} ∑19, {111)∑3 and {113)∑11 structural units and {110}∑1 and {001}∑1 single crystal units. The result of DV- Xα molecular orbital cluster calculation showed that the interstitial hydrogen atoms induced the palladium-hydrogen chemical bond which had a different energy level from the palladium-palladium bond. The component of the palladium-hydrogen bond at the grain boundaries was similar to those in the bulk palladium. It is clarified that electronic structure near the grain boundary is different from that in the perfect crystal. © 2005 The Japan Institute of Metals.

DOI： 10.2320/jinstmet.69.1010

Scopus

researchmap

Language：English  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

In the present study, the energy and atomic structure of the (110) symmetric tilt boundaries in palladium were evaluated using the molecular dynamics (MD) simulation and the electronic structures of hydrogen in the bulk and on the grain boundaries of palladium were calculated using the discrete-variational Xalpha (DV-Xalpha) method. The MD simulation revealed that the energy of the (110) symmetric tilt boundary of palladium depended on the misorientation angle and that there were large energy cusps at the misorientation angles which corresponded to the (111)Sigma3 and (113)Sigma11 symmetric tilt boundaries. The atomic structure of all &lt;110&gt; symmetric tilt boundaries could consist of the combination of the (331)Sigma19, (111)Sigma3 and (113)Sigma1 structural units and (110)Sigma1 and (001)Sigma1 single crystal units. The DV-Xalpha calculation showed that the interstitial hydrogen atoms in palladium induced the Pd-H chemical bond which had a different energy level than the Pd-Pd bond, The energy level and component of the Pd-H bonding on the grain boundaries in palladium were similar to those in the bulk palladium.

DOI： 10.2320/matertrans.45.2099

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Surface energies of alpha-Al2O3 were calculated using molecular dynamics (MD) method. It was found that the surface energy strongly depends on crystal orientation. The surface energy of (610) plane had the maximum value of about 13J.m(-2), while that of the other crystallographic planes ranged between 2 and 4J.m(-2). The fracture toughness of single crystal alpha-Al2O3 had relatively good correlation with surface energies of (0(2) over bar 10) and (0(2) over bar 12) planes. It was concluded that surface energies highly contributed to the cleavage fracture of (0(1) over bar 10) and (0(1) over bar 12) planes.

DOI： 10.2109/jcersj.112.46

Web of Science

researchmap

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

Silicon has been used as semiconductor devices. It is well known that silicon shows a sharp brittle-ductile transition and that silicon is a brittle material at the operative temperature of a device. Hence, it is important to understand fracture behavior to improve the reliability of a device. Because the surface energy, γs is considered to affect the fracture behavior of a brittle material, it is important to investigate the crystal orientation dependence of γs just after fracture in order to clarify the details of fracture mechanism. This study was carried out to clarify systematically the crystal orientation dependence of γs in silicon by molecular dynamics calculation. And it is also carried out to investigate the crystal orientation dependence of γs after 1098 K annealing and it was compared with γs just after fracture. It is revealed that γs of (1̄11) plane has the minimum value. This fact agrees with the experimental fact that cleavage plane of Si is {111}, It is also found that γs after 1098 K annealing is lower than that just after fracture. It is concluded that the decrease in γs was brought about by the reconstruction of the atoms.

DOI： 10.2320/jinstmet.68.86

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Ceramic Society of Japan  

Surface energies of α-Al2O3 were calculated using molecular dynamics (MD) method. It was found that the surface energy strongly depends on crystal orientation. The surface energy of (01̄10) plane had the maximum value of about 13 J·m-2, while that of the other crystallographic planes ranged between 2 and 4 J·m-2. The fracture toughness of single crystal α-Al2O3 had relatively good correlation with surface energies of (01̄10) and (01̄12) planes. It was concluded that surface energies highly contributed to the cleavage fracture of (01̄10) and (01̄12) planes.

DOI： 10.2109/jcersj.112.46

Scopus

researchmap

Event date： 2024.9

Language：Japanese   Presentation type：Poster presentation  

researchmap

Event date： 2024.4

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2024.4

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2024.4

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2024.3

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2024.3

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.4

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.10

Language：English   Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.4

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2020.10

Language：English   Presentation type：Oral presentation (general)  

researchmap

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：日本溶接協会四国地区溶接技術検定委員会  

researchmap

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：日本溶接協会四国地区溶接技術検定委員会  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本大学  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：九州工業大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都立大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：秋田大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京工業大学  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Kitakyushu Techno Center  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Pohang University of Science and Technology  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：埼玉大学  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Moscone Convention Cente  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Nagaoka University of Technology  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Pusan National University  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Hilton Daytona Beach & Ocean Center  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：新日鐵代々木研修センター  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岐阜大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：千葉工業大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：IHI横浜事業所  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岐阜大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：武蔵工業大学  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Kyushu University  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：新潟大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：新潟大学  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：京都大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：筑波大学  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Kasai Seminar House (Kyoto)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：筑波大学  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Hilton Daytona Beach & Ocean Center  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Paradise Hotel Busan  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：香川大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：香川大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Nishijin Plaza (Fukuoka)  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Nishijin Plaza (Fukuoka)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：山口大学  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Cairns Convention Center  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：北海道大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：山口大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：樺川荘(香川・塩江温泉)  

researchmap

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

Venue：休暇村讃岐五色台  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：香川大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：香川大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：香川大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：香川大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島工業大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都市大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：山形大学  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Greater Columbus Convention Center  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Hilton Hotel Seoul  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：The University of Tokyo  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都市大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：日本大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山理科大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島大学  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Centre des Congres de Quebec  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：休暇村讃岐五色台  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山理科大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：香川大学  

researchmap

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

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京理科大学  

researchmap

Presentation type：Oral presentation (general)  

Venue：Kyoto International Conference Center  

researchmap

Language：Japanese  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：茨城大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学  

researchmap

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

Venue：新居浜工業高等専門学校  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：株式会社総合車両製作所  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：沖縄コンベンションセンター  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Centara Hotel & Convention Centre Udon Thani  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：沖縄コンベンションセンター  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Swan & Dolphin Resort Hotel  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：岡山国際交流センター  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：香川大学  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Kasai Seminar House (Kyoto)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：香川大学  

researchmap

Presentation type：Oral presentation (general)  

Venue：高知工科大学  

researchmap

Presentation type：Oral presentation (general)  

Venue：首都大学東京  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：埼玉大学  

researchmap

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

Venue：The David L. Lawrence Convention Center  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鳥取大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州工業大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鳥取大学  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鳥取大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：四国地区溶接技術検定委員会  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：四国地区溶接技術検定委員会  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鳥取大学  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Kagawa University  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京理科大学  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Kagawa University  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：千葉工業大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：香川大学  

researchmap

Language：Japanese   Presentation type：Poster presentation  

researchmap

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

Venue：Cité des Sciences et de l ’ industrie (Paris)  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：McGill University, Montreal (Canada)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Belgorod National Research University, Saint-Petersburg (Russia)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Hilton Waikoloa Village  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学医学・工学研究科東京ブランチ  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋国際会議場  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：金沢大学  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Rio Hotel, Las Vegas  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：愛媛大学  

researchmap

Language：English   Presentation type：Oral presentation (general)  

Venue：Rio Hotel, Las Vegas  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Kagawa University  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Kagawa University  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：岡山国際交流センター  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Kagawa University  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：愛媛大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：四国地区溶接技術検定委員会  

researchmap

Language：Japanese   Presentation type：Poster presentation  

Venue：岡山国際交流センター  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：四国地区溶接技術検定委員会  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京工業大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：四国地区溶接技術検定委員会  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：Universiti Teknologi MARA  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：徳島大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：徳島大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：徳島大学  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京大学  

researchmap

Language：English   Presentation type：Poster presentation  

Venue：David L. Lawrence Convention Center  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京大学  

researchmap

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

researchmap

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

researchmap

researchmap

Author：Other 

researchmap

Author：Other 

researchmap

Author：Other 

researchmap

Author：Other 

researchmap