Aoyama, Takahito; Ogawa, Hiroaki; Kato, Chiaki; Ueno, Fumiyoshi
Metals, 11(3), p.511_1 - 511_13, 2021/03
The effect of Cu in bulk solution on pitting corrosion resistance of extra high purity type 316 stainless steel was investigated. Pitting occurred in 0.1 M NaCl-1 mM CuCl whereas pitting was not initiated in 0.1 M NaCl. Although deposition of Cu on the surface occurred regardless of potential region in 0.1 M NaCl-1 mM CuCl, Cu in bulk solution had no influence on the passive film formation. The decrease in pitting corrosion resistance in 0.1 M NaCl-1 mM CuCl resulted from the deposited Cu or Cu compound and continuous supply of Cu on the surface.
Kim, J. G.*; Bae, J. W.*; Park, J. M.*; Woo, W.*; Harjo, S.; Lee, S.*; Kim, H. S.*
Metals and Materials International, 27(2), p.376 - 383, 2021/02
Negyesi, M.; Amaya, Masaki
Oxidation of Metals, 94(3-4), p.283 - 299, 2020/10
Negyesi, M.; Amaya, Masaki
Oxidation of Metals, 92(5-6), p.439 - 455, 2019/12
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.
Xiong, Z.*; Naoe, Takashi; Futakawa, Masatoshi
Metals, 9(4), p.412_1 - 412_11, 2019/04
The effect of surface defects on the very high cycle fatigue (VHCF) behavior were investigated on the solution annealed (SA) and cold-rolled (CW) 316L. Surface defects were artificially created using indentation. VHCF test was conducted using an ultrasonic fatigue method. The results showed that the fatigue crack initiation was independent of the indent with the applied range of depth in this research. Furthermore, the critical depth of the indent was evaluated based on an empirical formula. In the case of SA, the VHCF strength was not affected when the indent depth was less than 40 m, which is consistent with the value obtained from the empirical formula. In the case of 20% CW, VHCF strength was not affected when the indent depth was less than 80 m. The results were much larger than the results obtained from the empirical formula and might have been caused by the plastic deformation, residual stress and probable deformation induced martensite transition around the indent.
Wan, T.; Saito, Shigeru
Metals, 8(8), p.627_1 - 627_22, 2018/08
Suzuki, Tomoya*; Ogata, Takeshi*; Tanaka, Mikiya*; Kobayashi, Toru; Shiwaku, Hideaki; Yaita, Tsuyoshi; Narita, Hirokazu*
Metals, 8(7), p.558_1 - 558_10, 2018/07
The refining of platinum group metals is based mainly on solvent extraction methods, whereas Ru is selectively recovered by distillation as RuO. Replacement of distillation byextraction is expected to simplify the purification process. To develop an effective extraction system for Ru, we analyzed the Ru species in HCl with UV-Vis and EXAFS spectroscopies, and we examined the properties of Ru extracted with N-2-ethylhexyl-bis(N-di-2-ethylhexyl-ethylamide) amine (EHBAA). EXAFS and UV-Vis spectra of Ru in HCl solutions revealed that the predominant Ru species in 0.5-10 M HCl solutions changed from [RuCl(HO)] to [RuCl] with the HCl concentration. The extraction percentages of Ru in the EHBAA system increased with increasing HCl concentration, reached 80% at [HCl] = 5 M, and decreased athigher HCl concentrations. EXAFS analysis of the extracted complex indicated that the Ru had 5 Cl and 1 HO in its inner coordination sphere. The similarity of the dependence on HCl concentrations of the extraction in the EHBAA system and the distribution profile of [RuCl(HO)] on [RuCl(HO)] suggested that the EHBAA extracted the pentachlorido species.
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, Hiroshi; Yamada, Rui*; Tsubaki, Shinki*; Imafuku, Muneyuki*; Sato, Shigeo*; Watanuki, Tetsu; Machida, Akihiko; Saida, Junji*
Metals, 6(1), p.12_1 - 12_11, 2016/01
Elastic deformation behaviors of as-cast and annealed eutectic and hypoeutectic Zr-Cu-Al bulk metallic glasses (BMGs) were investigated on a basis of different strain-scales determined by X-ray scattering and the strain gauge. The microscopic strains determined by Direct-space method (DSM) and Q-space method (QSM) were compared with the macroscopic strain measured by the strain gauge, and the difference in the deformation mechanism between eutectic and hypoeutectic Zr-Cu-Al BMGs was investigated by their correlation. The eutectic ZrCuAl BMG obtains more homogeneous microstructure by free-volume annihilation after annealing, improving a resistance to deformation but degrading ductility because of a decrease in the volume fraction of WBRs (Weakly-Bonded Regions) with relatively high mobility. On the other hand, the as-cast hypoeutectic ZrCuAl BMG originally has homogeneous microstructure, but loses its structural and elastic homogeneities because of nanocluster formation after annealing. Such structural changes after annealing might develop unique mechanical properties showing no degradations of ductility and toughness for the structural-relaxed hypoeutectic BMGs.
Sakai, Toru; Kasahara, Toshihiro*; Hijii, Keigo*; Ota, Hitoshi*; Nakano, Hiroki*
Synthetic Metals, 208, p.26 - 28, 2015/10
The S=1/2 three-leg spin nanotube with the ring exchange interaction at each plaquette is investigated using the numerical diagonalization of finite-size systems. The previous work suggested that the system without the ring exchange interaction has a spin excitation gap between the singlet ground state and the triplet excitation, because a spontaneous dimerization occurs in the ground state. The present study indicates that as the ring exchange increases, a quantum phase transition occurs at some critical value to another spin gap phase where the pattern of the dimerization is different from the initial one.
Itami, Toshio*; Saito, Junichi; Ara, Kuniaki
Metals, 5(3), p.1212 - 1240, 2015/09
A new kind of suspension liquid was developed by dispersing Ti nanoparticles (10 nm) in liquid Na, which was then determined by TEM (transmission electron microscopy) analysis. The volume fraction was estimated to be 0.0088 from the analyzed Ti concentration (2 at.%) and the densities of Ti and Na. This suspension liquid, Liquid Sodium containing nanoparticles of titanium (LSnanop), shows, despite only a small addition of Ti nanoparticles, many striking features, namely a negative deviation of 3.9% from the ideal solution for the atomic volume, an increase of 17% in surface tension, a decrease of 11% for the reaction heat to water, and the suppression of chemical reactivity to water and oxygen. The decrease in reaction heat to water seems to be derived from the existence of excess cohesive energy of LSnanop. The excess cohesive energy was discussed based on simple theoretical analyses, with particular emphasis on the screening effect. The suppression of reactivity is discussed with the relation to the decrease of heat of reaction to water or the excess cohesive energy, surface tension, the action as a plug of Ti oxide, negative adsorption on the surface of LSnanop, and percolation.
Sakai, Seiji; Matsumoto, Yoshihiro; Otomo, Manabu; Entani, Shiro; Avramov, P.; Sorokin, P. B.*; Naramoto, Hiroshi*
Synthetic Metals, 173, p.22 - 25, 2013/06
Tsuru, Tomohito; Aoyagi, Yoshiteru*; Shimokawa, Tomotsugu*; Kaji, Yoshiyuki
International Workshop on Bulk Nanostructured Metals; Proceedings Book, p.56_1 - 56_4, 2012/06
Bulk nanostructured metals composed of sub-micron diameter grains have a dramatic increase in the volume fraction located in the grain boundary region. Mechanical properties of the nano-structured metals cannot be predicted based on assumptions of the average quantity of collective motion of dislocations, and therefore it is increasingly necessary to understand the role of each grain and its effect on the plastic deformation. In the present study, a computational modelling based on large scale atomistic simulation is implemented to capture the effect of grain size and macroscopic mechanical properties.
Nakazato, Kyomi*; Nagamine, Takeaki*; Suzuki, Keiji*; Kusakabe, Takahiko*; Moon, H. D.*; Oikawa, Masakazu*; Sakai, Takuro; Arakawa, Kazuo
Biometals, 21(1), p.83 - 91, 2008/02
To clarify the relation of essential metals to cadmium (Cd) toxicity, we evaluated metallothionein expression and analyzed the subcellular distribution of essential metals using in-air micro-PIXE. Four mice were dosed orally with 100 mg/L of Cd in drinking water for 1.5 or 2 years. Compared to the control, the Cd-exposed mice markedly accumulated zinc in the liver and renal cortex. Elemental maps showed that a large amount of Cd was spatially combined with zinc in the 1.5y-Cd mouse. The data suggest that zinc may contribute to protect against oral-administrated Cd toxicity.
Nakamura, Hisashi; Hirabayashi, Takakuni; Akimoto, Jun*; Takahashi, Kenji*; Shindo, Hideaki*; Sakurai, Daihachiro*; Almansour, A.*; Okane, Toshimitsu*; Umeda, Takateru*
Int. J.Cast Metals Res., 11(5), p.339 - 343, 1999/00
no abstracts in English
Hashimoto, Kazuyuki; *
Technetium, Rhenium and Other Metals in Chemistry and Nuclear Medicine, p.325 - 328, 1999/00
no abstracts in English
Hishinuma, Akimichi; Wakai, Eiichi; Takaki, Seiichi*; Abiko, Kenji*
Proc. of Int. Conf. on Ultra-high purity base metals (UHPM-98), p.27 - 33, 1998/00
no abstracts in English
; Izui, Kazuhiko
Point Defects and Defect Interactions in Metals, p.705 - 707, 1982/00
no abstracts in English
Point Defects and Defect Interactions in Metals, p.873 - 875, 1982/00
no abstracts in English