All issues
Volume 79, Issue 9
Displaying 1-8 of 8 articles from this issue
- |<
- <
- 1
- >
- >|
Regular Article
-
Takashi Hasegawa, Shiori Kimura, Takunori Abukawa, Albert A. Valiullin ...2015 Volume 79 Issue 9 Pages 423-428
Published: 2015
Released on J-STAGE: September 01, 2015
JOURNAL FREE ACCESSThe relationship between magnetic phase transition temperatures (Curie temperature: Tc, ferromagnetic-antiferromagnetic transition temperature: T0) and lattice distortions in L10 FePt1−xRhx thin films (6 nm thick) were studied. Thin film depositions on varied substrates modifies lattice constants due to misfits between substrates and films, as well as residual stresses caused by rapid thermal annealing. Both epitaxially grown FePtRh thin films on MgO(001) substrate and nonepitaxially grown FePtRh thin films on SiO2 substrate exhibited the (001)-oriented L10 structure. The MgO/FePtRh films and the SiO2/FePtRh films had the almost constant a-values of 0.383 nm (1.0% of compressive strain to the FePtRh bulks) and 0.390 nm (0.8% of tensile strain to the FePtRh bulks) in average respectively, whereas the c-values decreased with the Rh composition (x). The c-axis distortion in both the MgO/FePtRh films and the SiO2/FePtRh films were the tensile strain in 0.25<x, and the strain values were 1.2% and 0.6%, respectively. Tc decreased with x in all of the samples (MgO/FePtRh films, SiO2/FePtRh films, and FePtRh bulks), and the reduction rates strongly depended on the c-values rather than values of a or x. T0 increased with x in all of the samples, and the incremental rates also strongly depended on the c-values.
View full abstractDownload PDF (2994K) -
Shunsuke Takaya, Shota Kasuga, Sujun Guan, Kohei Miyazawa, Hiroyuki Yo ...2015 Volume 79 Issue 9 Pages 429-433
Published: 2015
Released on J-STAGE: September 01, 2015
JOURNAL FREE ACCESSRecently, potassium titanate, formed from titanium oxide with high photocatalytic activity has been attracted much attention. In the present work, Ti films on Al2O3 balls were fabricated by mechanical coating technique (MCT). To obtain potassium titanate, the Ti films on Al2O3 balls were oxidized in air and the subsequent molten salt treatment with KNO3 and K2CO3 mixture. After that, the films were oxidized in air again. The microstructure and composition of the samples were characterized by SEM, EDS, and XRD. The photocatalytic activity was evaluated by measuring the degradation rate of methylene blue (MB) solution. The results show that the amorphous potassium titanate with nano-lamellar was formed on the surface by oxidizing the Ti films and the subsequent molten salt treatment with KNO3 and K2CO3 mixture. 6-pottasium titanate (K2Ti6O13) with nano-needle was obtained by oxidizing the amorphous potassium titanate with nano-lamellar in air. K2Ti6O13 with nano-needle showed high photocatalytic activity.
View full abstractDownload PDF (1756K) -
Yuta Kimura, Xiao Xu, Toshihiro Omori, Ryosuke Kainuma2015 Volume 79 Issue 9 Pages 434-440
Published: 2015
Released on J-STAGE: September 01, 2015
JOURNAL FREE ACCESSIn the present study, Ni content dependence of martensitic transformation (MT) temperatures in Ti50−XNi40+XCu10.0 alloys (X=0.0-3.0) was investigated in order to reveal the MT behavior at low temperatures. The Ti-Ni-Cu alloys are in B2 single-phase up to 42.4 at% Ni at 1363 K. B2/B19 or B19/B19′ MT temperatures decrease with increasing Ni and a lowest temperature of 124 K was detected. In the alloys with Ni compositions over 41.2 at%, pre-martensitic “intermediate” phase was detected by specific heat measurement. While the middle eigenvalue λ2 are close to 1.0, which were found independent of the Ni content, the thermal hysteresis, ΔThys increases with increasing Ni content, which is explained by drastic decrease in transformation entropy change.
View full abstractDownload PDF (2951K) -
Natsuko Kimura, Takeshi Kubota, Takahisa Yamamoto, Syuta Fukuoka, Yasu ...2015 Volume 79 Issue 9 Pages 441-446
Published: 2015
Released on J-STAGE: September 01, 2015
JOURNAL FREE ACCESSIn this study, heat treatment effect on the rapidly solidified Co-Fe alloys with high Co content was investigated for synthesizing a compact magnetic sensor with high-performance. The Co-Fe alloy ribbons with 71 and 75 at% Co and with 70 μm in the thickness were produced by a single Cu-roller rapid solidification, and subsequently heat treatment was conducted. For evaluation of the heat treatment effect, magnetic properties such as magnetization, coercivity, magnetostriction and susceptibility were measured as well as crystal structure.
The saturation magnetization and saturation magnetostriction for the Co71Fe29 ribbon annealed at 750℃ exhibited no remarkable change without any relation to the annealing time. On the other hand the Co75Fe25 alloy ribbon revealed annealing time dependency of both magnetization and magnetostriction, it was found that the short time annealing is effective in increasing the saturation magnetostriction. Maximal saturation magnetostriction of the Co75Fe25 alloy ribbon annealed at 750℃ reached to 96 ppm, 33% higher than that of the Co71Fe29 alloy. As a result magnetostrictive susceptibility for the annealed Co75Fe25 alloy ribbon became higher than that of the annealed Co71Fe29 alloy ribbon and it is considered that the optimal annealing Co75Fe25 alloy ribbon has excellent functionalities as an element material of the magnetic sensor.
View full abstractDownload PDF (2451K) -
Yuji Kunisada, Norihito Sakaguchi2015 Volume 79 Issue 9 Pages 447-451
Published: 2015
Released on J-STAGE: September 01, 2015
JOURNAL FREE ACCESSWe have investigated effects of hydrogen atoms on vacancy formation at fcc Fe(111) surfaces. To calculate hydrogen adsorption properties and vacancy formation energy, we performed first-principles calculations based on density functional theory with generalized gradient approximation. We considered fcc Fe(111) surfaces with monoatomic vacancies in second and third surface layers. We constructed exhaustive potential energy surfaces of hydrogen atoms in the vicinity of monoatomic vacancies, and obtained the most stable adsorption sites and corresponding adsorption energy. We found that hydrogen atoms can stably adsorb in the vicinity of monoatomic vacancies, while hydrogen atoms cannot be stable in the fcc Fe(111) subsurfaces without monoatomic vacancies. We also clarified that the vacancy formation energy is reduced by containing hydrogen atoms in the vicinity of vacancy sites. These results indicate that hydrogen atoms and vacancies can stabilize each other, which results in superabundant vacancies of fcc Fe(111) in hydrogen atmosphere.
View full abstractDownload PDF (1065K) -
Yutaka Kameyama, Hayato Takeshima, Jun Komotori, Koki Murasawa2015 Volume 79 Issue 9 Pages 452-460
Published: 2015
Released on J-STAGE: September 01, 2015
JOURNAL FREE ACCESSIn the present study the authors attempted to propose a new method to form Fe-Al intermetallic layer on a steel surface by using atmospheric-controlled IH-FPP (AIH-FPP). Surfaces of structural carbon steel as well as high-speed tool steel were modified by AIH-FPP using aluminum particles. Optical microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy revealed formation of solidified Al layer and underlying Fe2Al5 layer on the AIH-FPP-treated carbon steel substrate. Because of the existence of the intermetallic compound layer, the AIH-FPP-treated surface showed high hardness. It was assumed that deposition of aluminum particles and subsequent diffusion between aluminum deposit and substrate occurred during AIH-FPP process, forming the intermetallic layer. Longer anneal time after peening and higher temperature in AIH-FPP process increased in the thickness of the intermetallic layer and decreased in that of the solidified Al layer. AIH-FPP performed on the tool steel also formed Fe2Al5 layer and Al solidified layer. AIH-FPP temperature suitable for creating intermetallic was slightly higher for tool steel substrate than for carbon steel, implying that intermetallic layer formation was affected by carbon content in the substrate. Hot filament chemical vapor deposition (HF-CVD) successfully deposited thin film comprising diamond crystals on the AIH-FPP-treated steel substrate on which the intermetallic layer was formed. Graphite was contrastingly deposited on untreated steel substrate because of graphitization catalytic effect of Fe elements. It was clarified that the AIH-FPP using aluminum particles was a possible treatment to form hard intermetallic compounds and a candidate as a pre-treatment of CVD diamond coating for steel substrates.
View full abstractDownload PDF (4240K) -
Yoshikazu Mantani, Yoshito Takemoto2015 Volume 79 Issue 9 Pages 461-467
Published: 2015
Released on J-STAGE: September 01, 2015
JOURNAL FREE ACCESSThe purpose of this study was to investigate and discuss the relationship between the crystal structure of martensites and the material properties, such as the Young's modulus and internal friction, in quenched Ti-Nb alloys with plasto-elastic deformation. In the alloys, minimal Young's modulus was indicated by the α′ martensite of Ti15Nb, and maximal internal friction was indicated by the α″ martensite of Ti18Nb. After a weak plastic deformation of 5% rolling reduction, the Young's modulus of Ti-(15, 18, 20)Nb decreased, and the internal friction of Ti20Nb increased though that of Ti-(15, 18)Nb hardly changed. From the XRD profiles, the extreme values of the material properties were predicted to be associated with the unit volume and phases (hexagonal close-packed or orthorhombic) of the materials. It was also predicted to be associated with the change of phase from α′ to α″ and from α″ to α′+α″ or α″+α″ with different lattice parameters. Cyclic tensile test results after weak plastic deformation revealed characteristic changes in elastic incline, that is, an increase from ~40 GPa in Ti15Nb, and a decrease until ~40 GPa from the initial value followed by an increase in Ti18Nb and Ti20Nb. The consequent changing mechanism of material properties was suggested from the viewpoint of the changing behavior of the phase transformation and transition on martensites with plastic deformation or loaded elastic deformation.
View full abstractDownload PDF (3289K) -
Masataka Ijiri, Yoshito Takemoto2015 Volume 79 Issue 9 Pages 468-473
Published: 2015
Released on J-STAGE: September 01, 2015
JOURNAL FREE ACCESSA novel phenomenon recently observed in the tempering of Ti-4Fe-7Al alloy, has attracted considerable attention. This phenomenon is induced by the β→α″ transformation during tempering, and its noteworthy features are rapid hardening and a shape change in a U-shaped specimen. It is of interest whether this phenomenon occurs in other alloy systems. In this study, Ti-10Mo-7Al alloy, which contains a quantity of molybdenum corresponding to the lower β limit, was prepared and its microstructure, aging behavior, and shape change during tempering were investigated. An acicular α″ martensites were observed preferentially at the β grain boundaries in the quenched specimen, but it became invisible at the optical microscope level upon tempering. However, TEM (transmission electron microscopy) observation of the tempered specimen revealed nano size martensites instead of micron-size martensites. The novel phenomenon observed in the tempering of Ti-4Fe-7Al, was also confirmed to occur in Ti-10Mo-7Al alloy. In the heating of a U-shaped specimen, shape recovery occured first, then a shape return into a U-shape followed, and a curvature progressed more with increasing of temperature. As a result, the phenomenon was clarified to be a universal one. The transformation mechanism through tempering is explained as follows: Though aluminum addition to β-alloy raises the MS chemically, on the other hand, it causes a remarkable solution strengthening, which increases shear stress required for martensite transformation, and decreases the apparent MS. Consequently, the β phase is maintained by a rapid cooling. However, temperature rise decreases the shear stress, and the apparent MS increases to a chemically intrinsic one. If the MS increases beyond the tempering temperature, martensite transformation occurs abruptly.
View full abstractDownload PDF (3378K)
- |<
- <
- 1
- >
- >|