Shiro, Ayumi*; Okada, Tatsuya*; Shobu, Takahisa
Mechanical Engineering Journal (Internet), 8(6), p.21-00106_1 - 21-00106_8, 2021/12
The objective of the present study was to carry out observations of deformation and annealing processes of aluminum single crystals using a synchrotron radiation X-rays at SPring-8. Al single-crystalline samples having a 111 orientation parallel to the longitudinal direction were grown by a Bridgman method. The samples were deformed in tension to a nominal strain of 0.08 at room temperature using an in-line tensioning apparatus. Post-deformation annealing at 480 C was subsequently carried out in the same apparatus. A two-dimensional detector was used to detect multiple diffracted beams from the sample during the deformation and annealing processes. The volume irradiated by the X-ray beam was found to be composed of three regions having a small orientation difference, which was attributable to sub-grained microstructures of the sample. Detailed analyses of a diffraction spot intensity showed that the sub-grained microstructures were surpassed by dislocated microstructures with the increase in the tensile strain. During the post-deformation annealing, diffraction spots from a recrystallized grain first appeared at 180 s after the temperature reached 480 C. Coexistence of diffraction spots from the deformation matrix and recrystallized grain lasted only for about 22 s in the irradiated volume. The migration rate of the boundary between the deformation matrix and recrystallized grain was estimated to be of the order of several micrometers/s.
Shobu, Takahisa; Shiro, Ayumi*; Muramatsu, Toshiharu*
SPring-8/SACLA Riyo Kenkyu Seikashu (Internet), 9(5), p.318 - 323, 2021/08
Laser welding has already been put into practical use for various metal materials because the irradiation area is very small and the control is easy. In this study, we evaluated strain, stress, deformation, etc. near the processing affected area by high-energy synchrotron radiation X-ray diffraction method, which is one of the problems of laser welding of different materials that are expected to be put into practical use. As a result of internal deformation measurement of the bonding of dissimilar materials of copper and iron, it was confirmed that the copper side with a high coefficient of linear expansion was hardly deformed, strong tensile strain on the iron side, and a plastic deformation region on the heat-affected zone. In addition, a retained austenite phase, which is thought to be caused by the mixture of copper, was observed in the plastic deformation region of iron, and further problems were clarified in the evaluation of material strength in the mixed metallic materials.
Shobu, Takahisa; Shiro, Ayumi*; Kono, Fumiaki*; Muramatsu, Toshiharu; Yamada, Tomonori; Naganuma, Masayuki; Ozawa, Takayuki
Quantum Beam Science (Internet), 5(2), p.17_1 - 17_9, 2021/06
The automotive industries employ laser beam welding because it realizes a high energy density without generating irradiation marks on the opposite side of the irradiated surface. Typical measurement techniques such as strain gauges and tube X-rays cannot assess the localized strain at a joint weld. Herein high-energy synchrotron radiation X-ray diffraction was used to study the internal strain distribution of laser lap joint PNC-FMS steels (2- and 5-mm thick) under loading at a high temperature. As the tensile load increased, the local tensile and compressive strains increased near the interface. These changes agreed well with the finite element analysis results. However, it is essential to complementarily utilize internal defect observations by X-ray transmission imaging because the results depend on the defects generated by laser processing.
Hojo, Tomohiko*; Akiyama, Eiji*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Kinugasa, Junichiro*; Yuse, Fumio*
Corrosion Science, 177, p.108957_1 - 108957_9, 2020/12
Hydrogen assisted cracking on hemispherically-stretch-formed specimens of transformation induced plasticity-aided martensitic steel was investigated. Hydrogen charging induced cracking around the foot of the impression formed on the steel sheet, and the cracks propagated along the radial direction toward the hillside and the plains. Distributions of stress, plastic strain and volume fraction of retained austenite were analyzed employing the energy-dispersive X-ray diffraction method utilizing the synchrotron X-ray radiation at SPring-8. It was notable that the crack initiation took place in the region where the measured tensile stress was the highest. Influences of plastic strain and resulted martensitic transformation were also suggested.
Suzuki, Kenji*; Shiro, Ayumi*; Toyokawa, Hidenori*; Saji, Choji*; Shobu, Takahisa
Quantum Beam Science (Internet), 4(3), p.25_1 - 25_14, 2020/09
It is difficult to evaluate stress by the strain scanning method using a conventional diffractometer and a point detector since the two-dimensional diffraction pattern of a material composed of coarse grains does not have a ring but a spotty. To solve this problem, we proposed a double exposure method using a two-dimensional detector and monochromatized X-rays. In this study, we have developed a technique to apply that technique to white X-rays. The diffraction obtained by irradiating white X-rays for a material with of coarse grains becomes a Laue spot. Therefore, we have carried out developing a CdTe pixel two-dimensional detector that can limit the energy to be detected, and we evaluated the stress using that detector. As a result, we succeeded to measure the strain distribution of a bending specimen made to austenitic stainless steel. In the future, we would like to improve this technology and apply it to actual machine materials.
Hojo, Tomohiko*; Kumai, B.*; Koyama, Motomichi*; Akiyama, Eiji*; Waki, Hiroyuki*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Nagasawa, Akihiko*
International Journal of Fracture, 224(2), p.253 - 260, 2020/08
In the study, the pre-strain effect on hydrogen embrittlement property of the ultra-high-strength transformation-induced plasticity -aided bainitic ferrite steel was investigated towards application for automobile frame parts. 3-10% tensile pre-strain suppressed hydrogen-induced mechanical degradation relative to total elongation while 12-15% pre-strained specimen did not exhibit elongation after hydrogen charging. The advantageous effect of the 3-10% pre-strain was attributed to the suppression of crack initiation related to retained austenite. The TRIP by pre-straining decreased the volume fraction of retained austenite before hydrogen charging, thereby reducing existing probabilities of preferential crack initiation sites and propagation paths. Conversely, high pre-strain such as 12-15% does not effectively work due to work hardening resulting in increases in hydrogen embrittlement susceptibility and a significant increase in hydrogen content due to the multiplication of dislocations.
Shobu, Takahisa; Shiro, Ayumi*; Yoshida, Yutaka*
Zairyo, 69(4), p.343 - 347, 2020/04
Dislocation density is a very important physical quantity in the evaluation of fatigue of metallic materials. Generally, the dislocation density is evaluated by a scanning electron microscope. Recently, a method generated the dislocation density from the width of the X-ray diffraction profile has been proposed. In this study, we report the application of this technology to synchrotron radiation. Five diffraction profiles were obtained with a two-dimensional detector during tensile loading of the austenitic stainless steel SUS316L, and the dislocation density was calculated from the line profile analysis. As a result, the dislocation density increased sharply after plastic deformation, and the value was in good agreement with the result separately measured with a scanning electron microscope. In the future, it is expected that the line profile analysis will contribute to the elucidation of the mechanism of fatigue fracture by measuring the dislocation density from the local area in materials.
Miyakawa, Susumu*; Ito, Toshimasa*; Iwahori, Keisuke*; Aoyama, Yoshihiko*; Kubo, Ryosuke*; Murata, Shinji*; Shobu, Takahisa; Shiro, Ayumi*; Kajiwara, Kentaro*
Zairyo, 69(4), p.308 - 314, 2020/04
White etching area which looks white with nital corrosive liquid may be recognized at the flaking part of a rolling bearing on which high contact stress of several GPa is applied repeatedly. Up to now, studies of white etching area of a ball have been less than studies of white etching area of inner and outer rings. In this study, as part of the flaking mechanism explication with white etching area of a ball, internal residual stress distributions of ball by using high energy white X-ray of SPring-8 (A method) and laboratorial X-ray measurement equipment (B method) were investigated. The former was modified by surface residual stress according to B method. The latter was modified by releasing stress in the form of electrolytic polishing. The results showed modified residual stress distributions almost agree qualitatively.
Bae, S.*; Jee, H.*; Suh, H.*; Kanematsu, Manabu*; Shiro, Ayumi*; Machida, Akihiko*; Watanuki, Tetsu*; Shobu, Takahisa; Morooka, Satoshi; Geng, G.*; et al.
Construction and Building Materials, 237, p.117714_1 - 117714_10, 2020/03
Sano, Tomokazu*; Eimura, Takayuki*; Hirose, Akio*; Kawahito, Yosuke*; Katayama, Seiji*; Arakawa, Kazuto*; Masaki, Kiyotaka*; Shiro, Ayumi*; Shobu, Takahisa; Sano, Yuji*
Metals, 9(11), p.1192_1 - 1192_13, 2019/11
The purpose of the present study was to verify the effectiveness of dry laser peening (DryLP), which is the peening technique without a sacrificial overlay under atmospheric conditions using femtosecond laser pulses on the mechanical properties such as hardness, residual stress, and fatigue performance. After DryLP treatment of the laser-welded 2024 aluminum alloy, the softened weld metal recovered to the original hardness of base metal, while residual tensile stress in the weld metal and heat-affected zone changed to compressive stresses. The fatigue life almost doubled at a stress amplitude of 180 MPa and increased by a factor of more than 50 at 120 MPa. As a result, DryLP was found to be more effective for improving the fatigue performance of laser-welded aluminum specimens with welding defects at lower stress amplitudes.
Suzuki, Kenji*; Shobu, Takahisa; Shiro, Ayumi*
Zairyo, 68(4), p.312 - 317, 2019/04
Materials after thermal processing such as welding often have coarse grains. To understand the residual stress after processing is very important from the viewpoint of the soundness of the structure. In this study, we proposed a double exposure method that combines a two-dimensional detector and high-energy synchrotron radiation as an X-ray stress measurement method for materials with coarse grains, and confirmed its practicality. As a result of measuring the residual stress of the plastic bending specimen and the indentation specimen of the aluminum alloy (A5052), the effectiveness of this measurement method was clarified because the residual stress distribution was in good agreement with the finite element analysis.
Bae, S.*; Jee, H.*; Kanematsu, Manabu*; Shiro, Ayumi*; Machida, Akihiko*; Watanuki, Tetsu*; Shobu, Takahisa; Suzuki, Hiroshi
Journal of the American Ceramic Society, 101(1), p.408 - 418, 2018/01
Despite enormous interest in calcium silicate hydrate (C-S-H), its detailed atomic structure and intrinsic deformation under an external load are lacking. This study demonstrates the nanostructural deformation process of C-S-H in tricalcium silicate (CS) paste as a function of applied stress by interpreting atomic pair distribution function (PDF) based on in situ X-ray scattering. Three different strains in CS paste under compression were compared using a strain gauge and the real and reciprocal space PDFs. PDF refinement revealed that the C-S-H phase mostly contributed to PDF from 0 to 20 whereas crystalline phases dominated that beyond 20. The short-range atomic strains exhibited two regions for C-S-H: I) plastic deformation (0-10 MPa) and II) linear elastic deformation (10 MPa), whereas the long-range deformation beyond 20 was similar to that of Ca(OH). Below 10 MPa, the short-range strain was caused by the densification of C-S-H induced by the removal of interlayer or gel-pore water. The strain is likely to be recovered when the removed water returns to C-S-H.
Akita, Koichi; Nakatani, Hayato*; Ogihara, Shinji*; Shobu, Takahisa; Shiro, Ayumi*; Igawa, Naoki; Shimojo, Yutaka
SPring-8/SACLA Riyo Kenkyu Seikashu (Internet), 6(1), p.105 - 108, 2018/01
no abstracts in English
Ojima, Mayumi*; Shiro, Ayumi*; Suzuki, Hiroshi; Inoue, Junya*; Shobu, Takahisa; Xu, P. G.; Akita, Koichi; Nambu, Shoichi*; Koseki, Toshihiko*
Zairyo, 66(6), p.420 - 426, 2017/06
Toyokawa, Hidenori*; Saji, Choji*; Kawase, Morihiro*; Wu, S.*; Hurukawa, Yukihito*; Kajiwara, Kentaro*; Sato, Masugu*; Hirono, Toko*; Shiro, Ayumi*; Shobu, Takahisa; et al.
Journal of Instrumentation (Internet), 12(1), p.C01044_1 - C01044_7, 2017/01
We have been developing CdTe pixel detectors combined with a Schottky diode sensor and photon-counting ASICs. The hybrid pixel detector was designed with a pixel size of 200 micro-meter by 200 micro-meter and an area of 19 mm by 20 mm or 38.2 mm by 40.2 mm. The photon-counting ASIC, SP8-04F10K, has a preamplifier, a shaper, 3-level window-type discriminators and a 24-bits counter in each pixel. The single-chip detector with 100 by 95 pixels successfully operated with a photon-counting mode selecting X-ray energy with the window comparator and stable operation was realized at 20C. We have performed a feasibility study for a white X-ray microbeam experiment. Laue diffraction patterns were measured during the scan of the irradiated position in a silicon steel sample. The grain boundaries were identified by using the differentials between adjacent images at each position.
Sano, Mutsumi*; Takahashi, Sunao*; Watanabe, Atsuo*; Shiro, Ayumi*; Shobu, Takahisa
Materials Research Proceedings, Vol.2, p.609 - 614, 2017/00
Dislocation densities of GlidCop with compressive strain applied at high temperature were examined by X-ray line profile analyses with synchrotron radiation. In order to evaluate the dislocation density, we applied the modified Williamson-Hall and modified Warren-Averbach method. The dislocation densities of GlidCop with compressive strain from 0.011-0.04 were in the range of 5.7-8.010m.
Watanabe, Masashi*; Yonezawa, Toshio*; Shobu, Takahisa; Shiro, Ayumi; Shoji, Tetsuo*
Corrosion, 72(9), p.1155 - 1169, 2016/09
Sato, Shigeo*; Onuki, Yusuke*; Shobu, Takahisa; Shiro, Ayumi*; Tashiro, Hitoshi*; Todoroki, Hidekazu*; Suzuki, Shigeru*
Kinzoku, 86(8), p.654 - 660, 2016/08
no abstracts in English
Liss, K.-D.*; Funakoshi, Kenichi*; Dippenaar, R. J.*; Higo, Yuji*; Shiro, Ayumi*; Reid, M.*; Suzuki, Hiroshi; Shobu, Takahisa; Akita, Koichi
Metals, 6(7), p.165_1 - 165_22, 2016/07
Titanium aluminides find application in modern light-weight, high-temperature turbines, such as aircraft engines, but suffer from poor plasticity during manufacturing and processing. Huge forging presses enable materials processing in the 10 GPa range and hence, it is necessary to investigate the phase-diagrams of candidate materials under these extreme conditions. Here we report on an in-situ synchrotron X-ray diffraction study in a large-volume-press of a modern ( + ) two-phase material, Ti-45Al-7.5Nb-0.25C, under pressures up to 9.6 GPa and temperatures up to 1686 K. At room temperature, the volume response to pressure is accommodated by the transformation rather than volumetric strain, expressed by apparently high bulk moduli of both constituent phases. Crystallographic aspects, specifically lattice strain and atomic order are discussed in detail. It is interesting to note that this transformation takes place despite an increase in atomic volume, which is due to the high ordering energy of . Upon heating under high pressure, both the eutectoid and -solvus transition temperatures are elevated, and a third, cubic -phase is stabilized above 1350 K. Earlier research has shown that this -phase is very ductile during plastic deformation, essential in near-conventional forging processes. Here, we were able to identify an ideal processing window for near-conventional forging, while the presence of the detrimental -phase is not present under operating conditions. Novel processing routes can be defined from these findings.
Suzuki, Kenji*; Shobu, Takahisa; Shiro, Ayumi; Zhang, S.*
Advanced Materials Research, 996, p.76 - 81, 2014/08