Yoshitaka Matsukawa

Yoshitaka Matsukawa
Kumamoto University | Kumadai · Department of Materials Science and Engineering

PhD

About

81
Publications
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Publications

Publications (81)
Article
Full-text available
The migration of point defects, for example, crystal lattice vacancies and self-interstitial atoms (SIAs), typically occurs through three-dimensional random walk in crystalline solids. However, when vacancies and SIAs agglomerate to form planar clusters, the migration mode may change. We observed nanometer-sized clusters of vacancies exhibiting one...
Article
The crystal orientation of body centered cubic (bcc) precipitates embedded in hexagonal close packed (hcp) matrix is usually assumed to follow the so-called Burgers orientation relationship; however, this orientation relationship may not be maintained in the case where the precipitation occurs in parallel with the recrystallization of matrix. The Z...
Article
The surface oxide film of a Zr−2.5Nb alloy subjected to long term corrosion at 633 K in simulated primary coolant of pressurized water reactors has been analyzed. The primary concerns were whether Nb precipitates exhibit amorphization upon oxidation, and whether they dissolve into the matrix, as suggested by previous studies. Their behavior is of p...
Article
By combining atom probe tomography (APT) with transmission electron microscopy (TEM) we have attempted to identify the stage at which solute clusters transform into compounds crystallographically distinct from the matrix, in the precipitation of the G-phase (Ni 16 Si 7 Mn 6) from ferrite solid solution subjected to isothermal annealing at 673 K. Ba...
Article
A potential factor dominating the obstacle strength of second phase precipitate particles in dispersion strengthening is the crystallographic mismatch between the matrix phase and the second phase; however, yet this concept has not been fully assessed by experiments and simulations. In the present study, we experimentally investigated the obstacle...
Article
Recrystallization behavior of a two-way cold rolled 12Cr ODS steel during annealing in the range of 1273–1473 K was systemically investigated by means of scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and hardness testing. Results show that original grains with <110> axis were rotated to <111> axis...
Chapter
This is an open access article available from <https://www.intechopen.com/online-first/crystallography-of-precipitates-in-metals-and-alloys-1-analysis-of-crystallography>. This chapter and the following chapters describe crystallography of second-phase precipitate particles in metals and alloys. The focus of this chapter is placed on technical asp...
Chapter
This is an open access article available from <https://www.intechopen.com/online-first/crystallography-of-precipitates-in-metals-and-alloys-2-impact-of-crystallography-on-precipitation-ha>. Following the previous chapter, this chapter describes crystallography of second-phase precipitate particles in metals and alloys; the focus of this chapter is...
Article
A combination of ion-accelerator irradiation, nanoindentation tests, and electron backscatter diffraction analysis was utilized to probe the crystal orientation dependence of irradiation-induced hardening in a Zr alloy. The nanohardness at the [0001] orientation exhibited the highest value, which gradually decreased when the orientation deviated fr...
Article
Tensile properties and microstructure of a Zr–1.8Nb alloy subjected to 140-MeV C⁴⁺ ion irradiation at 573 K up to 5.3 dpa have been investigated by using 0.18 mm-thick tensile specimens. Irradiation damage was introduced into the tensile specimens homogeneously over entire thickness using a variable energy degrader. Irradiation-induced strengthenin...
Article
The interaction between oxide particles and dislocations in a 9Cr-ODS ferritic steel is investigated by both static and in situ TEM observation under dynamic straining conditions and room temperature. The measured obstacle strength ( ) of the oxide particles was no greater than 0.80 and the average was 0.63. The dislocation loops around some coars...
Article
In this work, the mechanical behavior of as-received and hydrogenated Zircaloy-4 fuel claddings was investigated by the newly developed advanced expansion due to compression (A-EDC) test and the conventional uniaxial tension (UT) test at room temperature, in order to, respectively, understand the hydride-induced embrittlement in tube longitudinal a...
Article
Irradiation with high-energy particles induces athermal migration of point defects, which affects defect reactions at low temperatures where thermal migration is negligible. We conducted molecular dynamics simulations of vacancy migration in iron and copper driven by recoil energies under electron irradiation in a high-voltage electron microscope....
Article
Full-text available
The precipitation of carbides in F82H steel and its model steel (Fe-0.2TaC) were investigated by transmission electron microscopy (TEM) and extracted residue tests (ERT). The effects of tempering on the precipitation in F82H steels were elucidated on the basis of the characterization of carbides, as well as the quantitative estimation of precipitat...
Article
A new testing technique named advanced expansion due to compression (A-EDC) has been developed with an attempt to study the hoop mechanical behavior of Zircaloy-4 cladding under the pellet-cladding mechanical interaction (PCMI) and the presumed reactivity-initiated accident (RIA). The Zircaloy-4 used in this work showed elongated grains in the tube...
Article
Full-text available
This study investigates the microstructure and mechanical property in heat affected zone (HAZ) between F82H and SUS316L jointed by 4 kW fiber laser welding at different parameters such as laser scan rate and beam position. OM/FE-SEM observation, EPMA analysis and nano-indentation hardness test were utilized to characterize the microstructure and ev...
Article
Full-text available
The microstructure of the 12Cr-ODS steel was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD) techniques. The results showed that the microstructure consisted of fine and elongated grains, high density of dislocations, and large concentr...
Article
Oxide Dispersion Strengthened (ODS) ferritic/martensitic steels have an excellent high temperature strength primarily due to a dislocation pinning effect of nanometric oxide particles. In the present work, the interaction between oxide particles and dislocations in 9CrODS ferritic steel was investigated by both static TEM observation and in-situ TE...
Article
We performed in situ observation of one-dimensional (1D) migration of self-interstitial atom (SIA) clusters in iron under electron irradiation at 110–300 K using high-voltage electron microscopy. Most 1D migration was stepwise positional changes of SIA clusters at irregular time intervals at all temperatures. The frequency of 1D migration did not d...
Article
Full-text available
High-Cr steel (Fe-8Cr-2W-0.4Mn-0.2V-0.06Ta, so-called F82H steel) is one of the candidate structure materials for fusion blanket system, and its dissimilar welding technology to stainless steel (SUS316L) is an inevitable issue. Fiber laser welding is a promising technique to joint F82H and SUS materials, because of its non-mandatory vacuum environm...
Article
Two types of oxide dispersion strengthening (ODS) steels (i.e. 12Cr-ODS-NIFS and 12Cr-ODS-IMR) with similar chemical compositions were produced through different fabrication processing. A systematic comparison was performed to investigate the effects of different fabrication processing on microstructure and mechanical properties of ODS steels. Comp...
Article
Mo-modified Zr–1.2Nb alloys were prepared and the effects of Mo addition on precipitation in Zr–Nb alloys were elucidated. It was found that an increase of Mo content decreased α→(α+β) phase transformation temperature in Zr–Nb alloys. A new kind of precipitate, β-(Nb, Mo, Zr), was identified in the Mo-containing alloys. These particles are formed b...
Article
Impurity segregation at the interface between b-Nb precipitates and a-Zr matrix in Zr-2.5 wt.%Nb alloy was investigated by complementary analysis with positron annihilation spectroscopy (PAS) and atom probe tomography (APT). Fe segregation and Fe-decorated defects were found at the interface. PAS also suggested that Fe was segregated to a concentra...
Article
Full-text available
Expansion due to compression (EDC) test has been applied to evaluate the performance of nuclear fuel claddings where pellet-cladding mechanical interaction (PCMI) is introduced by swelling of fuel pellets and is triggered by the larger hoop deformation of the pellets, especially during accidental transients. The purpose of this study is to modify t...
Article
Full-text available
Publication details, including instructions for authors and subscription information: The Zr–Nb alloys were modified by doping of Mo as a minor alloying element to seek for the nuclear fuel cladding materials with better characteristics. The effects of Mo on microstructural evolution and mechanical properties in Zr–Nb alloys were systematically inv...
Article
Full-text available
For self-interstitial atom (SIA) clusters in various concentrated alloys, one-dimensional (1D) migration is induced by electron irradiation around 300 K. But at elevated temperatures, the 1D migration frequency decreases to less than one-tenth of that around 300 K in iron-based bcc alloys. In this study, we examined mechanisms of 1D migration at el...
Article
Full-text available
The alloying effects of Sn, Nb, Cr, and Mo on zirconium alloys were elucidated and compared. Electron backscatter diffraction, transmission electron microscopy, tensile test, and fractographic observation were jointly utilized to carry out detailed microstructural characterization and mechanical property evaluation. Results show that Mo is the most...
Article
In this work, thermal aging experiments on 9Cr-ODS steel were carried out at 973 K from 100 h up to 10,000 h, and grain structural evolution was investigated mainly focusing on analyses by electron backscatter diffraction (EBSD). The EBSD maps revealed no significant morphological changes in the matrix grain structure under the long-term aging. Gra...
Article
Full-text available
Ultrafine-grained interstitial-free steel fabricated by the accumulative roll-bonding method was subjected to tensile tests and analyses of AFM, TEM and XRD to identify the effects of interaction between dislocations and grain boundaries (GB) on the deformation mechanism. The AFM analyses indicated that the main deformation mechanism of this materi...
Article
This paper presents a microstructural study of a surveillance test specimen from the Loviisa-1 reactor in Finland, which is a Russian-type pressurized water reactor (VVER-440), after initial irradiation to a neutron fluence of 2.5 Â 10 19 n/cm 2 (E > 1 MeV), post-irradiation annealing at 475 °C for 100 h and re-irradiation to three different fluenc...
Article
The microstructures and the hardness of stainless steel weld overlay cladding of reactor pressure vessels subjected to neutron irradiation at a dose of 7.2 Â 10 19 n cm À2 (E > 1 MeV) and a flux of 1.1 Â 10 13 n cm À2 s À1 at 290 °C were investigated by atom probe tomography and by a nanoindentation technique. To isolate the effects of the neutron...
Article
Full-text available
Three-dimensional atom probe technique was used to observe the three-dimensional solute distribution around the extended edge dislocation in neutron irradiated austenitic stainless steel. The segregation of Si, Cr and Ni to stacking fault (SF) was observed. Solute segregation to the SF was larger than that of the Shockley partial dislocation. The b...
Article
Full-text available
To examine effects of the grain boundary (GB) and dislocation on the deformation mechanism for ultra-fine-grained (UFG) and coarse-grained (CG) interstitial-free (IF) steels at room temperature, tensile tests and several types of microscopy were conducted for each steel. Atomic force microscopy revealed that the contribution of grain-boundary slidi...
Conference Paper
Full-text available
The Mg-Zn-Y alloys with long period stacking ordered (LPSO) structures have been studied by positron annihilation lifetime (PAL), coincidence Doppler broadening (CDB) and atom probe tomography (APT). The positron lifetime for all the Mg-Zn-Y alloys is in a range of 221~225 ps, very close to the positron lifetime for pure Mg bulk, 222 ps. Low temper...
Article
Radiation-induced segregation (RIS) of solute atoms at a grain boundary (GB) in 304 stainless steel (SS), neutron-irradiated to a dose of 24 dpa at 300 °C in the fuel wrapper plates of a commercial pressurized water reactor, was investigated using laser-assisted atom probe tomography (APT). Ni, Si, and P enrichment and Cr and Fe depletion at the GB...
Article
In situ straining in a transmission electron microscope was performed in order to investigate dislocation interactions with a prismatic loop, which as a mobile obstacle is expected to be displaced by the strain-field of dislocation prior to physical contact. It was found that when a gliding dislocation approached a critical distance, the prismatic...
Article
The effect of thermal aging on microstructural changes in stainless steel submerged arc weld-overlay cladding of reactor pressure vessels was investigated using atom probe tomography (APT). In as-received materials subjected to post-welding heat treatments (PWHTs), with a subsequent furnace cooling, a slight fluctuation of the Cr concentration was...
Article
Irradiation-induced precipitates in a 304 stainless steel, neutron-irradiated to a dose of 24dpa at 300°C in the fuel wrapper plates of a commercial pressurized water reactor, were investigated by laser-assisted three-dimensional atom probe. A high number density of 4×1023m−3 of Ni–Si rich precipitates was observed, which is one order of magnitude...
Article
Full-text available
Defect-sensitive and element-selective measurements on ultrathin chrome, copper, and gold layers embedded in aluminium are presented using coincident Doppler broadening spectroscopy (CDBS) with a monoenergetic positron beam. The amounts of positrons implanted in the layers of different thicknesses are calculated and compared with the experimentally...
Article
In situ straining experiments conducted in a transmission electron microscope have been performed to reveal how dislocations interact with and annihilate isolated stacking-fault tetrahedra, common defect clusters in irradiated face-centered cubic metals. Comparison of the experimental results with the predictions from molecular dynamics computer si...
Article
The destruction processes of stacking fault tetrahedra (SFTs) induced by gliding dislocations were examined by transmission electron microscopy (TEM) in situ straining experiments for SFTs with edge lengths ranging from 10 to 50 nm. At least four distinct SFT destruction processes were identified: (1) consistent with a Kimura–Maddin model for both...
Article
The destruction process of large non-truncated stacking fault tetrahedra (SFTs) induced by gliding dislocations was examined by in situ transmission electron microscope straining experiments. Three different destruction processes were observed: a triangular Frank loop remained after the collapse (Type 1), the whole SFT was incorporated into a glidi...
Article
Full-text available
Large-scale atomistic modelling has demonstrated that the dynamic interactions of dislocations in thin films have a number of remarkable features. A particular example is the interaction between a screw dislocation and a stacking fault tetrahedron (SFT) in Cu, which can be directly compared with in situ observations of quenched or irradiated fcc me...
Article
The collapse of stacking-fault tetrahedra (SFT) by gliding dislocations was observed in in situ straining experiments in a transmission electron microscope (TEM). A stacking-fault tetrahedron was collapsed by intersection with a gliding perfect dislocation: only the base portion divided by the gliding plane of the dislocation annihilated, while the...
Article
The current understanding of defect production fundamentals in neutron-irradiated face centered cubic (FCC) and body centered cubic (BCC) metals is briefly reviewed, based primarily on transmission electron microscope observa-tions. Experimental procedures developed by Michio Kiritani and colleagues have been applied to quantify defect cluster size...
Article
The high number density of stacking fault tetrahedra (SFTs) observed in irradiated fcc metals suggests that they should contribute to radiation-induced hardening and, therefore, taken into account when estimating mechanical properties changes of irradiated materials. The central issue is describing the individual interaction between a moving disloc...
Article
Dynamic observation of the microstructure of quenched gold during deformation in a transmission electron microscope revealed that stacking fault tetrahedra (SFTs) having perfect pyramid structure were collapsed by direct interaction with moving screw dislocations. Although a recent molecular dynamics computer simulation study found that truncation...
Article
Full-text available
Recent molecular dynamics and transmission electron microscopy results on irradiated metallic materials are reviewed, with an emphasis on defect production in the displacement cascade and the fluence- and temperature-dependent accumulation of defect clusters. Materials analyzed include Fe, V, Cu, austenitic stainless steel, V4%Cr4%Ti, and ferritic/...
Article
Based on computer simulations, we examined a new mechanism of plastic deformation that has been proposed to operate in tensile fracture of metal foils. We constructed a Au crystal containing high concentration of vacancies and/or one subjected to large elastic tensile strain using embedded atom method (EAM) potential, and then calculated transmissi...
Article
The effect of deformation speed on defect structures introduced into bulk gold specimens at 298 K has been investigated systematically over a wide range of strain rate from ε′=10−2 to 106 s−1. As strain rate increased, dislocation structure changed from heterogeneous distribution, so-called cell structure, to random distribution. Also, stacking fau...
Article
Ductile fracture of metals produces a thin foil portion, which is observable by transmission electron microscopy, at the fractured edge. The thin foil portion shows unusual deformation microstructure, which contains no dislocations, but contains vacancy-type point defect clusters at extraordinarily high density. Dynamic observation of the deformati...
Article
Materials responses under non-equilibrium conditions, especially in the state far-from-equilibrium, have been attracting great interest. Although of limited use, there are some tools available for investigating the phenomena, e.g. theoretical approaches such as non-equilibrium thermodynamics or atomistic computer simulation. The present study cente...
Article
Dislocation-free plastic deformation, which occurs under extraordinarily high internal stress comparable to ideal strength of metals, was discovered in thin foil portion produced by ductile fracture of fcc Au by dynamic observation of the deformation process , , , and . In the present study, the deformation process of thin foil portion in other fcc...
Article
Heavy plastic deformation of fcc metal thin foils to fracture has been found recently to proceed without involving dislocations, and it results in the formation of high density of vacancy clusters. Thin foil specimens of bcc metals such as V and Mo were plastically deformed to fracture in in situ elongation experiments under an electron microscope....
Article
Plastic deformation of crystalline metals not involving dislocations is confirmed to occur during elongation to fracture of thin films, and the possibility of dislocation-free deformation during high-speed deformation of bulk samples is suggested. A general requirement for the occurrence of deformation by the new mechanism is extremely high interna...
Article
Full-text available
Evidence for plastic deformation of crystalline metal thin films without involving dislocations is presented. Direct observation of the films during deformation under an electron microscope confirmed the absence of dislocations even for heavy deformation. In fcc metals, including aluminum, deformation leads to the formation of an anomalously high d...
Article
Full-text available
Variation in defect microstructures introduced by compression of three fcc metals, Al, Cu and Ni, was investigated over a wide range of strain rate, from 10(-2) to 10(6)/s. Dislocations formed under high-speed deformation are randomly distributed, whereas dislocations formed under low-speed deformation develop into cell structures, the transition b...