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Volume 67, Issue 11
Displaying 1-11 of 11 articles from this issue
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Hiroshi Kimura, Takashi Uchino2003 Volume 67 Issue 11 Pages 629-634
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThis article describes the system design and the development of the thermo-mechanical processing for the high-speed forging with multi-variable control, in which one can evaluate the superplastic flow and achieve a nanocrystalline control. This nanoprocessing consists of three discrete components, the thermal system and the pulse system equipped with the manipulative pulse current discharging and the mechanical system with servo-control hydraulic pressing. The process analysis for the isochronal forging at a constant displacement rate permits us to derive the strain rate sensitivity exponent(m) of approximately 0.4 in the constitutive equation of \dotεm=Aσexp(−Q⁄kT) for the superplastic flow in full density nanocrystalline (Ti50Al50)90Fe10 with the average crystallite size of 20 nm. For the full density amorphous Ti50Al50 sample, the isochronal forging under the constant load leads to a relatively high plastic strain rate of approximately 1×10−2 s−1 at 977 K and the compressivility of 0.89 at the maximum in the die of this experiment, and exhibits the Newtonian viscous flow that is given by a relation of η=η0exp(Qv⁄kT) in a supercooled liquid. The apparent activation energy(Q) for nanocrystalline Ti50Al50 in isochronal forging is derived at 113 kJ·mol−1 that is a nearly quarter of the value(467 kJ·mol−1) of the amorphous alloy.View full abstractDownload PDF (538K) -
Hajime Matsumoto, Eiichi Sukedai, Hatsujiro Hashimoto2003 Volume 67 Issue 11 Pages 635-642
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSClarification of onset time of formation and formation behaviour of aged ω-phase crystals from as-quenched ω-phase crystals is essential to understand β-ω phase transformation in β-Ti and Zr alloys. The onset time and the formation behaviour in a Ti-15 mass%Mo alloy due to aging at 323 K has been investigated using in-situ observation of morphology change of ω-phase crystals, and EDS analysis of Mo contents in ω-phase crystals and their surrounding matrices. It is found that the difference of Mo contents between as-quenched ω-phase crystals and their surrounding matrices is hardly detected. The onset time determined by the Mo contents analysis is 25.2 ks, which is shorter than that determined by the morphology change observations. Aged ω-phase crystals grow at as-quenched ω-phase crystals. Due to aging at 373 K for 54 ks and at 423 K for 21.6 ks, the growth of aged ω-phase crystals was observed, and these results suggest that aged ω-phase crystals grow due to Ostwalt ripening mechanism.View full abstractDownload PDF (2579K) -
Tomohisa Wataya, Masaaki Yoshikawa, Takashi Tanaka, Hiromitsu Kojima2003 Volume 67 Issue 11 Pages 643-646
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to improve the wettability and storage stability of Sn-Zn system Pb-free cream solders, minute amounts of Mg, Al, Cu, Pb, and Sb were added to the Sn-8Zn-1Bi Pb-free alloy, and its properties were evaluated.
The results obtained are:
—Mg and Al additions were effective in improving wettability,
—the addition of Al increased the amount of unmelted solder, and
—the addition of Mg caused degradation of storage stability due to an increase in solder viscosity.
Addition of the other elements did not improve the wettability. The combination of Mg and Al additions was found to improve wettability and storage stability, leading to stable wettability. Results of AES surface analyses showed that the solder with Mg and Al additives forms an Mg-Al-composite oxide film in the surface layer, which suppresses Zn oxidation observed in non-added solders. The suppression of Zn oxidation and the formation of a thin Mg-Al-composite film contribute to the wettability and storage stability improvements.View full abstractDownload PDF (384K) -
Tetsuyoshi Suzuki, Yoshihisa Kaneko, Satoshi Hashimoto2003 Volume 67 Issue 11 Pages 647-651
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSA new white gold was fabricated by alloying iron and chromium to gold matrix. Au-Fe-Cr alloys of various chemical compositions were prepared by arc melting first in order to examine plastic workability, which was estimated by cold rolling and bending tests. The workability tended to increase at the alloys which had high Au and low Cr contents. With a view to confirming color tone which has been important for white golds, surface color of alloy was evaluated on the basis of Yxy and L*a*b* color spaces. It was recognized that the surface color of the Au-Fe-Cr alloy was almost identical to that of a conventional Au-Pd-Cu-Ag white gold. Tensile deformation properties of wiredrawn specimens were investigated at the alloys showing the high plastic workability. It was found that ultimate tensile strengths of some as-drawn Au-Fe-Cr alloys exceeded 1 GPa, which is comparable with the strength of an Au-Ni-Cu-Zn white gold. Au-14%Fe-1%Cr alloy exhibited the highest strength among the Au-Fe-Cr alloys tested in the present study.View full abstractDownload PDF (864K) -
Toshikazu Akahori, Mitsuo Niinomi, Keita Ishimizu, Hisao Fukui, Akihir ...2003 Volume 67 Issue 11 Pages 652-660
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSFatigue properties of Ti-29Nb-13Ta-4.6Zr underwent various thermomechanical processings were investigated in order to establish the optimal thermomechanical processing conditions for getting excellent fatigue properties.
Precipitated α phase in Ti-29Nb-13Ta-4.6Zr aged at 673 K for 259.2 ks after cold rolling presents very fine needlelike phase as compared with precipitated α phase in Ti-29Nb-13Ta-4.6Zr aged at 673 K for 259.2 ks after solution treatment at 1063 K for 3.6 ks or aged at 723 K for 259.2 ks after cold rolling. Ti-29Nb-13Ta-4.6Zr aged at 723 K for 259.2 ks after cold rolling shows the greatest fatigue strength in both low cycle fatigue and high cycle fatigue life regions, and the fatigue limit, which is around 770 MPa, is nearly equal to that of hot-rolled Ti-6Al-4V ELI with equiaxed α structure.View full abstractDownload PDF (1460K) -
Masahiro Kitada2003 Volume 67 Issue 11 Pages 661-667
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe microstructures and corrosion behavior of tin thread made in the late Edo period have been investigated. Specimens are obtained from brocades made using the tin thread and from a sample book of tin brocade. Reflectance is measured with a spectrophotometer. Fine structures are observed using a transmission electron microscope. An X-ray diffractometer and X-ray photospectrometer are used to identify corrosive matter. Sn foil glued on Japanese paper shows a brownish black color spectrum. The thickness of the corroded Sn foil is 8∼10 μm. SnO2, SnO, and Sn3O2(OH)2 are detected in the corroded Sn foil. The top layer consists of the most stable SnO2, and there is a SnO layer beneath the SnO2 layer. A Sn3O2(OH)2 layer exists between the SnO layer and the unreacted Sn layer. From these results, corrosion has been promoted in the order of Sn3O2(OH)2, SnO and SnO2.View full abstractDownload PDF (2242K) -
Masaaki Yamamura, Takao Yamaguchi, Imao Nagasaka, Setsuro Hiraoka, His ...2003 Volume 67 Issue 11 Pages 668-674
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe spectral emissivity of metals has been analyzed by the linear equation governing motion of electrons. Such analysis is sufficient if we discuss the spectral emissivity for relatively wide wavelength range from macroscopic viewpoint.
When we determine the true temperature from a measured color temperature, we need the accurate spectral emissivity in the narrow wavelength range in the vicinity of the visible ray. But the spectral emissivity of color metals, such as gold and copper, varies roughly depending on wavelength in that range. Therefore the spectral emissivity obtained by the linear dissipation theory does not agree enough to be measured due to the nonlinear characteristic of this phenomenon.
In this paper, we take into account the nonlinearity in the equation governing free electrons motion, and using the solution of this equation we derive the nonlinear optical dispersion formula which estimates dependency of the wavelength on spectral emissivity. As the result, by using this formula we have succeeded to describe more accurately the spectral emissivity of color metals which varies roughly with wavelength.View full abstractDownload PDF (329K) -
Seung-Hun Kang, Yuho Deguchi, Kaoru Yamamoto, Keisaku Ogi, Makoto Shir ...2003 Volume 67 Issue 11 Pages 675-680
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe thermal and metallographic analysis revealed that the solidification of Inconel 718 alloy proceeds in order of primary γ at 1615 K, γ/NbC eutectic at 1561 K, and γ/Ni2Nb eutectic at 1452 K. On the other hand, equilibrium evaluation using Thermo-Calc expresses the following solidification sequences; primary γ at 1633 K, followed by γ/NbC eutectic at 1555 K. The γ/Ni2Nb eutectic phase doesn’t appear in the equilibrium calculation, indicating that the γ/Ni2Nb phase crystallizes as non equilibrium eutectic phase.
The partition coefficients of alloying elements to primary γ and eutectic phases were also determined experimentally (k(Exp.)) and compared with the values estimated with Thermo-Calc (k(T-C)). The behaviors of alloying elements during solidification were estimated by using k(Exp.) and k(T-C) on the Clyne-Kurz model. It was found that both of them are in a good agreement.View full abstractDownload PDF (631K) -
Nobuhito Sakaguchi, Mitsuo Niinomi, Toshikazu Akahori, Takashi Saito, ...2003 Volume 67 Issue 11 Pages 681-687
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSEffect of Nb content on microstructure, tensile properties and elastic modulus of Ti-XNb-10Ta-5Zr alloys made by a sinter-forged method for biomedical applications was investigated. Ti-30Nb-10Ta-5Zr, which is the simplified compositional alloy of Ti-29Nb-13Ta-4.6Zr developed for biomedical applications, has been selected as the basic alloy composition and, Nb contents of the alloy were varied from 0 through 40 mass%.
Blended elemental powder metallurgy method was applied to fabricate these alloys. The alloying elements powders were mixed and pressed to form green products by a cold isostatic pressing (CIP) machine. Green products were then sintered at 1573 K for 57.3 ks in a vacuum of about 1.33×10−3 Pa. Subsequently, they were forged and swaged at 1223 K in air. Finally, heat treatment at 1123 K for 1.8 ks in air to remove residual strain was done on the swaged bar. Tensile tests and elastic modulus measurements and mocrostructural observations on different Nb content were carried out.
The microstructure of the alloy containing 0 mass%Nb shows single α phase. Other phases such as α″ phase, ω phase and β phase become to be recognized with increasing Nb composition of Ti-XNb-10Ta-5Zr alloys. Microstructures of the alloys containing over 30 mass%Nb show single β phase.
Elastic moduli of Ti-XNb-10Ta-5Zr alloys decrease with increasing Nb contents. However, 15Nb, 20Nb and 25Nb alloys, whose microstructures contain ω phase, show a tendency of the increase of elastic moduli. These tendencies of elastic moduli are the same with general binary titanium alloy systems.
The alloy containing 25 mass%Nb, whose microstructure have ω phase, shows the largest elongation. Tensile properties of the alloys containing over 30 mass%Nb, which have same microstructures, change a lot. These phenomena are caused by the change of deformation mechanism of β phase.View full abstractDownload PDF (1242K) -
2003 Volume 67 Issue 11 Pages 688a
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSPlease see Errata PDF Wrong:[Please see pdf] Right:[Please see pdf]View full abstractDownload PDF (113K) -
2003 Volume 67 Issue 11 Pages 688b
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSPlease see Errata PDF Wrong:Fig. 4 High resolution micrograph of a specimen aged for 10 s at 473 K after quenching from 853 K. Moiré pattern region (α) and streak contrast region (β) can be seen., Fig. 5 High resolution micrograph of a specimen aged for 20 s at 473 K after quenching from 853 K. Moiré pattern region (α) and streak contrast region (β) can be seen. Right:Fig. 4 High resolution micrograph of a specimen aged for 10 s at 473 K after quenching from 853 K. Moiré pattern region (β) and streak contrast region (α) can be seen., Fig. 5 High resolution micrograph of a specimen aged for 20 s at 473 K after quenching from 853 K. Moiré pattern region (β) and streak contrast region (α) can be seen.View full abstractDownload PDF (113K)
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