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Volume 78, Issue 9
Displaying 1-6 of 6 articles from this issue
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Regular Article
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Manami Uemitsu, Masanori Enoki, Satoshi Iikubo, Hiroshi Ohtani2014 Volume 78 Issue 9 Pages 327-336
Published: 2014
Released on J-STAGE: September 01, 2014
JOURNAL FREE ACCESSA thermodynamic analysis of phase equilibria in the Mn-Bi-Sb ternary system has been carried out with specially focusing on the stability of the ferromagnetic NiAs-type αMnBi phase by an addition of Sb. In this study, the Gibbs free energy of this phase was evaluated using first-principles calculations combined with the cluster variation method (CVM), and the obtained results as well as the available experimental data on phase boundaries and thermodynamic properties were introduced in the analysis. The calculated results enabled the reproduction of experimental results on both the phase equilibria and thermodynamic properties obtained from first-principles calculations and the CVM. The calculations indicated that the stable region of NiAs-type αMnBi phase is expanded with increasing Sb content in alloys.
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Hoshiaki Terao, Hideaki Kobiki, Katsumi Yamada, Naoyuki Kanetake2014 Volume 78 Issue 9 Pages 337-343
Published: 2014
Released on J-STAGE: September 01, 2014
JOURNAL FREE ACCESSW-Cu and Mo-Cu materials have been applied for heat-sink application. Low thermal expansion coefficient is required as well as high thermal conductivity for heat-sink. Chromium is the same 6A group element as W and Mo, but its thermal properties, namely thermal expansion coefficient and thermal conductivity are a little inferior to these of W and Mo. Furthermore the Chromium is dissolved slightly in Cu during solution treatment and precipitated by aging treatment. In this paper, to improve the thermal expansion coefficient of Cr-Cu close to that of Mo-Cu and W-Cu, the effect of Cr precipitation treatment on thermal expansion coefficient of Cr-Cu was investigated. A commercial alloy 1.1 mass%Cr-Cu and 50 mass%Cr-Cu produced by powder infiltration process were prepared for the investigation. They were solution treated without quenching and aged at various temperatures to make relatively large Cr precipitates, and then their thermal expansion coefficient were measured. As the result, the drastic decrease of thermal expansion coefficient was discovered in the bottom at 823 K. The phenomenon was estimated to relate to larger warp contrast by coherent Cr precipitate at 823 K. In the rolled plates of both Cr-Cu materials, anisotropic behavior of the phenomenon was observed in the rolling and transverse directions.
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A. Ozawa, C. Watanabe, R. Monzen, N. Muramatsu2014 Volume 78 Issue 9 Pages 344-349
Published: 2014
Released on J-STAGE: September 01, 2014
JOURNAL FREE ACCESSThe effect of thermomechanical treatment on the strength of a Cu-21 mass%Ni-5.5 mass%Sn alloy was investigated. The alloy was cold-rolled to a 50% or an 80% reduction and then peak-aged at 400℃ (50R-A or 80R-A), or first peak-aged at 400℃ and then rolled to a 50% or an 80% reduction (A-50R or A-80R). The A-50R alloy exhibited a higher 0.2% proof stress σ0.2 of 1120 MPa and a higher tensile strength σu of 1200 MPa than the 50R-A alloy, and the A-80R alloy exhibited larger values of σ0.2=1200 MPa and σu=1310 MPa than the 80R-A alloy. The higher proof stress of the A-50R or A-80R alloy than the 50R-A or 80R-A alloy was ascribed to the higher dislocation density and the smaller deformation twin boundary spacing. The value of σu=1310 MPa for the A-80R alloy is considerably larger than those of commercial Cu-(20~22) mass%Ni-(4.5~5.7) mass%Sn alloys produced by cold rolling and subsequent aging.
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Keijiro Nakasa, Takashi Kubo, Akihiro Yamamoto, Tsunetaka Sumomogi2014 Volume 78 Issue 9 Pages 350-358
Published: 2014
Released on J-STAGE: September 01, 2014
JOURNAL FREE ACCESSArgon ion sputter etching was applied to steels and copper alloys at a radio frequency power of 150 or 250 W for 0.9 to 10.8 ks. Cone- or ridge-shaped protrusions with many secondary fine protrusions were formed on the surface. The sizes of the protrusions were typically comparable to the wavelength range of visible light, i.e. 400 nm to 700 nm, and that of near-infrared ray, i.e. 700 nm to 2.5 μm. Their absorbance of visible light and near-infrared ray was more than 90%, and the absorbance decreased with increasing wave length. These characteristics of the protrusions along with the high heat-resistance of stainless steels and the high heat-conductivity of copper alloys are suitable for the solar selective materials. The exposure of the protrusions formed on the copper alloys to oxygen gas or air just after the sputter etching increased the absorbance of visible light as well as infrared ray with an appearance of the spectrum of Cu2O near the wavelength of 16 μm.
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Shigeru Saito, Toshiyuki Takashima, Katsumi Miyama, Toshio Narita, Lin ...2014 Volume 78 Issue 9 Pages 359-363
Published: 2014
Released on J-STAGE: September 01, 2014
JOURNAL FREE ACCESSThe formation of the inter-diffusion zone (IDZ) between NiCrAlY coating and Nb substrate during vacuum heat treatment was investigated. A NiCrAlY coating was applied on Nb substrate by cathode arc deposition. Vacuum heat treatments were carried out at 800℃, 900℃ and 1000℃ for 2 h. SEM, EPMA, EDS and XRD were performed to analyze the microstructure of the IDZ and the results were interpreted using the 1002℃ isothermal ternary Nb-Ni-Cr phase diagram. It was found that at 800℃ the IDZ has a single NbNi3 layer; at 900℃ the IDZ consists of an outer NbNi3 layer, a thin intermediate NbCr2(HT) layer and an inner Nb7Ni6 layer; at 1000℃ the IDZ has three well-developed layers: an outer NbNi3 layer, an intermediate NbCr2(HT) layer and an inner Nb7Ni6 layer. A small amount of Cr exists in both NbNi3 and Nb7Ni6 phases as solid solution, and a large amount of Ni in NbCr2(HT) phase as solid solution.
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Kazuyuki Shimizu, Masahiko Nishijima, Akira Takeuchi, Takeshi Nagase, ...2014 Volume 78 Issue 9 Pages 364-368
Published: 2014
Released on J-STAGE: September 01, 2014
JOURNAL FREE ACCESSThe nanocrystallization of three kinds of nanocrystalline, soft magnetic FeSiBPCu alloys as well as Fe76Si9B10P5 alloy were investigated by using irradiation and ultrahigh voltage electron microscopy. MeV electron irradiation was selected instead of conventional annealing to clarify the early stage of primary crystallization, which is completed during heating in conventional annealing. The dynamic observations of the Fe85Si2B8P4Cu1, Fe85Si2B12Cu1, and Fe86Si2B8P4 as well as Fe76Si9B10P5 amorphous alloys revealed that α-Fe nanocrystals precipitated at the irradiated region. The amorphous phase could not maintain its original structure; furthermore, α-Fe nanocrystals precipitated via irradiation-induced crystallization, which resembles thermal crystallization. The dynamic observations of the irradiation-induced nanocrystallization behavior clarified the effect of Cu and P elements on the incubation time and growth behavior of the α-Fe nanocrystals embedded in the amorphous matrix during nanocrystallization. This is the first detailed evaluation of the early stage in the nanocrystallization of an amorphous phase in NANOMET by in situ TEM observations and the MeV electron irradiation technique.
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