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Volume 54, Issue 7
Displaying 1-15 of 15 articles from this issue
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Masahiko Ikeda, Shin-ya Komatsu, Takashi Sugimoto, Kiyoshi Kamei1990 Volume 54 Issue 7 Pages 743-751
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe composition and temperature dependence of resistivity ρ was investigated for Ti-5-50 mass%V alloys quenched from 1173 K. The retained β phase after water quenching from 1173 K was observed in the alloys containing more than 11.9 mass%V. At room temperature, distinct X-ray diffraction peaks of ω phases were observed only in the Ti-15 mass%V alloy. The negative temperature dependence appeared between 20 and 35 mass%V.
In a way similar to the Ti-Mo and Ti-Nb systems, the anomalous resistivity-temperature curves of the Ti-V alloys may be classified into three types; the curves with a maximum, a negative temperature coefficient and minimum, respectively. Starting and final temperature, ωs and ωf of athermal ω phase formation were estimated through a translational ρ-T curves fitting. Both ωs and ωf were lowered with increasing V content.
Selected area electron diffraction patterns were taken at suitable temperature intervals during both cooling and heating of the samples. In the Ti-25 mass%V alloy, relatively sharp ω reflections appeared during cooling to 123 K in TEM, and these reflections disappeared during re-heating to ca. 300 K. Also, in the Ti-35 mass%V alloy, β reflections and weak diffuse scattering were observed at room temperature (ca. 293 K), and the intensity of diffuse scattering, associated with an athermal ω phase, increased during cooling to 125 K. This result was supported from the evidence that the negative temperature dependence of ρ was related to the formation and disappearance of the athermal ω.
Finally, the measurement of the temperature dependence of resistivity has higher sensitivity than diffractometry to detect the athermal ω formation.View full abstractDownload PDF (1624K) -
Yoshihiro Takahara, Atsushi Morita, Tsutomu Takeda, Hidehiko Matsuda1990 Volume 54 Issue 7 Pages 752-757
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSStructural relaxation processes have been investigated for Fe60Ni20B10Si10 and Fe50Ni30B10Si10 amorphous alloys by differential scanning calorimetry. The activation energy spectra P(E) for the processes were estimated on the basis of AES (Activation Energy Spectra) model. The spectra (P(E) ) were asymmetric in shape. The P(E) in both the amorphous alloys shifted to the higher side of E with increasing temperature as a result of the contribution of relaxation centers activated at higher temperatures. The activation energies for relaxation over the annealing temperatures investigated were distributed in a range from 164.1 kJ/mol (1.7 eV) to 202.7 kJ/mol (2.1 eV). This explains well that the P(E) results from the relaxation centers in which the short-range rearrangements of metal-metal pairs could take place.View full abstractDownload PDF (859K) -
Tomoyasu Aihara, Mikio Kaji, Tadashi Igarashi1990 Volume 54 Issue 7 Pages 758-763
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThermomigration is a mass transport phenomenon under the influence of a temperature gradient. This effect has been found in the applications of high temperature heat transfer to have a pronounced influence on the thermal stability of functionally gradient materials (FGM). FGM consists of two or more compositions and phases having continuously changing distributions. The numerical analysis by the finite difference method is applied to the compositional distribution change induced by the thermomigration in two-phase βTi/TiC and V/V2C FGM’s or alloys having a uniform compositional distribution. The results show a considerable difference in the compositional distribution change between the two alloy systems, with a proportional relationship between the temperature conditions and the duration time for βTi/TiC FGM’s.View full abstractDownload PDF (729K) -
Akira Nozue, Keiji Ohki, Tadatsune Okubo1990 Volume 54 Issue 7 Pages 764-771
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe purpose of the present study is to improve the mechanical properties of the beta-quenched and beta-annealed specimens with little strain due to processing, only by heat-treatment. Control of volume fraction, morphology and distribution of alpha is of great importance in achieving desired mechanical properties with a good combination of yield strength, elongation and fracture toughness. Accordingly, a special (S) solution treatment has been proposed to obtain bimodal structures of equiaxed and acicular alphas. The microstructures of the specimens subjected to the S solution treatment consisted of nearly equiaxed and acicular alphas with the matrix of the tempered martensite. As a result, the mechanical properties became almost equivalent to the specimens of the double solution treatment, which has been widely known to exhibit an optimum combination in the specimens with the strain due to forging and rolling. The fracture toughness for the S solution treatment was found to increase due to zone shielding and crack deflection. Finally, the S solution treatment was applied to welded materials.View full abstractDownload PDF (5610K) -
Shuichi Furuya, Noboru Soga1990 Volume 54 Issue 7 Pages 772-777
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe repassivation potential for crevice corrosion (ER crev.) of commercial aluminum alloys was measured successfully using the method developed for stainless steel. The measured ER crev. was then compared with the pitting potential of various alloys. The results showed that the ER crev. of aluminum alloys was less noble than the pitting potential by 150 to 200 mV, confirming that crevice corrosion is the more easily occurring type even in aluminum alloys just as in the case of stainless steel.
Further, with commercial Al-Mg alloys, the greater the amount of magnesium contained, the less noble the repassivation potential for crevice corrosion (ER crev.) became, thus suggesting that the greater the amount of magnesium contained, the more prone they were to crevice corrosion as well as pitting.
The ER crev. of Al-Mg alloy and Al-Mn alloy using 99.99%Al, were also measured. In Al-Mg alloy, ER crev. became less noble as the amount of magnesium contained increased. In Al-Mn alloy, on the other hand, it became more noble as the amount of manganese contained increased.
In case of both high purity alloys, however, the value of ER crev. became less noble than crevice corrosion (ER crev.) of commercial aluminum alloys by about 300 mV. This is thought to be because Fe, which is contained in commercial Al Alloys as an impure element, acts as a powerful cathode and shifts the potential in a less noble direction.View full abstractDownload PDF (774K) -
Michiko Yoshitake, Kazuhiro Yoshihara1990 Volume 54 Issue 7 Pages 778-783
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTi film was deposited onto Cu substrate by a r.f. magnetron sputtering method. After deposition, the specimen was heated in a vacuum and the reactions between Cu and Ti through diffusion were investigated with Auger electron spectroscopy, X-ray photoelectron spectroscopy and the X-ray diffraction method.
At the temperatures between 700 and 800 K, a small amount of Cu diffused onto the surface of the Ti film, and the surface concentration of Cu was kept about 5%. Its diffusion coefficient was 3×1016 m2s−1, which is thousand times larger than the value obtained by extrapolating the diffusion coefficient of Cu in bulk Ti to 700 K. The segregated Cu existed near the surface of the Ti film, and Cu seems to form a two-dimensional compound. This diffusion behavior was blocked by the oxygen surface contamination.
Above 800 K, after a small amount of Cu diffused rapidly onto the surface of the Ti film, the surface concentration of Cu increased further. In this process, Cu and Ti reacted at the interface and some kinds of intermetallic compounds were formed in layer. The value of the diffusion coefficient of Cu in this process was close to that in bulk Ti. The intermetallic compound, γ-TiCu, Ti3Cu4 and TiCu3 were formed. However, γ-TiCu and Ti3Cu4 disappeared with heating for a long time. It is reported that Ti2Cu, γ-TiCu, Ti3Cu4, Ti2Cu3, TiCu2 and Ti2Cu7 are formed from ‘bulk Ti’-‘bulk Cu’ couple. In this work, from ‘film Ti’-‘bulk Cu’, we did not observe the formation of Ti2Cu, Ti2Cu3, TiCu2 nor Ti2Cu7. We observed the formation of TiCu3 which is not formed from ‘bulk Ti’-‘bulk Cu’ couple.View full abstractDownload PDF (837K) -
Yoshinori Wakamatsu, Toshitada Shimozaki, Masami Onishi1990 Volume 54 Issue 7 Pages 784-793
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSZinc dross specimens containing 3 mass%Fe were heated with various amounts of Al-50 mass%Zn alloy at 773 to 1023 K, in order to investigate the formation process of Fe-Al alloy crystals in the Al addition method employed for Zn recovery from the dross formed at the bottom of a hot-dip galvanizing bath.
In the dross specimens heated with the amounts of the Al-Zn alloy equal to 1-3, 3.6-6 and 8-12% of their weight, crystals of α phase, α and Fe2Al5 phases and Fe2Al5 phase are formed, respectively. Although crystals of δ1(FeZn7) and ζ(FeZn13) phases are also formed together with these crystals, they decrease gradually with the lapse of heating time and disappear completely when the specimens are heated with the amount of the Al-Zn alloy more than 4.4% of their weight. The decrease in the amounts of δ1 and ζ crystals is due to the decrease in Fe concentration in molten Zn by crystallization of the α and Fe2Al5 phases and their disappearance time decreases with increase in heating temperature and amount of Al-Zn alloy.
The maximum value of area fraction and minimum Al content of the Zn matrix (η phase) are obtained by heating with the amount of Al-Zn alloy equal to about 5% of the weight of the zinc dross specimen. The optimum amount of Al in the Al addition method seems to be about 0.8 times the Fe content in the dross, although the amount has been regarded as 1.5 times.View full abstractDownload PDF (3921K) -
Masayuki Yoshiba, Hiroshi Wada, Takashi Sakaki, Masatoshi Kato1990 Volume 54 Issue 7 Pages 794-801
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to evaluate the utility of a high purity Cr plate developed by an improved processing technique with powder metallurgy for a high temperature corrosion resistant structural material, the molten salt corrosion tests were performed by the laboratorial salt coating method at 1073-1173 K using the V2O5-Na2SO4-NaCl systems of salt mixtures, and the corrosion behavior was investigated from various points of view. The isocorrosion contour; the corrosion map, was established for high purity Cr in the tertiary salt system, suggesting the strong dependence on a NaCl concentration of corrosion resistance. The corrosion kinetics of the representatitve molten salt systems, corresponding to vanadium pentoxide attack and hot corrosive environments were also investigated, to reveal its conformity to a nearly parabolic rate law in both environments. Different aspects of the corrosion behavior were discussed in connection with scale analyses, and it was suggested that Cr2O3 could be always formed at the metal/scale interface to provide a protective barrier. Furthermore, the effect of the pre-oxidation treatment on the corrosion resistance improvement for the high purity Cr was investigated to confirm the improvement in corrosion performance under a variety of molten salt environments.View full abstractDownload PDF (1977K) -
Mechanism of Pyrolysis of Amorphous Silicon Carbide Fibre Obtained from Polycarbosilane as PrecursorToshio Shimoo, Masaki Sugimoto, Kiyohito Okamura1990 Volume 54 Issue 7 Pages 802-808
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe mechanism of pyrolysis of silicon carbide fibre (Nicalon) has been investigated at temperatures from 1673 to 1973 K under an argon atomsphere. The rate of pyrolysis was measured by means of thermogravimetry, and the formation of the pyrolysis product was examined by chemical analysis and TEM observation.
The rate of pyrolysis depends on temperature. The mass loss measured was attributable to both SiO and CO gas evolved by the pyrolysis. During pyrolysis, the three-dimensional growth of the cristallite of SiC was observed in the fibre. As a result, the amorphous fibre was crystallized in β-SiC.
The rate of pyrolysis was described by the Avrami-Erofeev equation. The order of this equation was m=1.3. The Arrhenius plots of the rate constants gave the apparent activation energy of 484 kJ/mol. These results showed that the rate was controlled by the crystal growth of SiC involving the diffusion of carbon in the fibre.View full abstractDownload PDF (2124K) -
Kazuyuki Hokamoto, Li-Qun Ruan, Minoru Yamamori, Akira Chiba, Masahiro ...1990 Volume 54 Issue 7 Pages 809-815
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe formation of wavy interfaces in the multilayered plate made by the explosive-bonding of metal sheets is investigated under various bonding condition.
Homogeneous wave length in the bonded plate of copper sheets with a given thickness can be obtained by (1) the use of a thick driver plate which minimizes the decrease of the plate velocity due to collision, (2) the control of the stand-off distance between the copper sheets arranged in the bonding apparatus, and (3) the reasonable choice of the quantity by which the flying behavior of the driving plate is determined.
In the bonding of the metal sheets of different thickness, uniform wave shapes can be obtained by regulating the stand-off distance between the sheets.
For the bonding of the different metal sheets, an approximately linear relationship is found between the wave length and the kinetic energy loss. The linear constant varies with the combination of metal sheets.View full abstractDownload PDF (1345K) -
Kimio Kubo1990 Volume 54 Issue 7 Pages 816-825
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA model is proposed to describe metals solidifying dendritically. The basic equations for temperatures and compositions of liquid, solid and liquid-solid interface are derived by modeling microscopical heat and mass flows, dendrite shape and constitutional undercooling. In addition, a theoretical equation of dendrite cell size is developed. Calculated values of permeability and dendrite cell size by the obtained model coincide well with the experimental values.View full abstractDownload PDF (1576K) -
Masako Nakahashi, Makoto Shirokane, Hiromitsu Takeda1990 Volume 54 Issue 7 Pages 826-831
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThis study discusses TLP bonding for Ni-base heat resistant alloys MarM-247 and IN939, using filler metals specially designed and fablicated to flexible foils by rapid solidification processes. Filler metals, selected by metallographic studies, produce almost the same microstructure in TLP bonds as in the base metal.
The mechanical properties for TLP bonds with the filler metals have been estimated by the stress-rupture test, which is the severest test used to evaluate bonding strength, at 1253 K. The test has demonstrated that TLP bonds with selected filler metals have strength equivalent to the base metal strength.
The results have also revealed that bonding pressure is indispensable for MarM-247 to gain high bonding strength.View full abstractDownload PDF (1835K) -
Takeo Sakurai, Tomoya Minegishi, Shotaro Morozumi, Kazuo Hamajima1990 Volume 54 Issue 7 Pages 832-838
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBonding structures of zirconium diboride, ZrB2, Joined to active metals, Ti, Zr and Hf, containing alloys, were investigated by optical microscopy. EPMA and X-ray diffraction methods. The results obtained are as follows:
(1) When a Cu/active metal/Cu three-foil filler was used for brazing at temperatures between 1273 and 1673 K for 1200 s and at 1273 K for 600 to 3600 s, the active metal migrated and segregated at the bonding interface of the brazing metal and ZrB2. The thickest active-metal-segregated layer was obtained in the joint bonded with Ti containing the filler alloy, even though the standard free energy of formation of boride is the highest in Ti of the other three IVa transition group metals.
Since the Ti-segregated layer increased linearly with the increase of temperature and time, it was deduced that the Ti atom might migrate as a cation in the molten or solid filler alloys by any electric motive force.
(2) When an Al/active metal/Al foil filler was used for brazing at 1173 K for 1200 s, the active metal also migrated and segregated at the bonding interface, though the segregated layer was very thin in comparison with that in the Cu filler alloy. This thin layer was thought to be due to the low brazing temperature at which the solubility of Ti in liquid Al is very limited.
(3) When Ni/active metal/Ni foil fillers were used for brazing at 1473 K for 1200 s, joining was carried out by solid state diffusion bonding. The segregation of the active metal at the bonding interface was observed, accompanied by diffusion of Ni into the ZrB2 matrix.View full abstractDownload PDF (1323K) -
Hideo Nakae, Kazuhiro Yamamoto, Kenji Sato1990 Volume 54 Issue 7 Pages 839-846
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSWetting of graphite by liquid aluminum and Al-Si alloys was studied at 1273 K in purified He-3 vol%H2 with the Meniscography.
The wetting was divided into three characteristic stages with the change in adhesive tension (Fa): (1) Initial wetting with decreasing Fa due to dewetting of the specimen by the melt, (2) quasi-equilibrium in wetting with constant Fa, and (3) spreading of the melt at the surface of graphite with increasing Fa.
The highest wetting speed was obtained with graphite/Al-20 mass%Si. SEM observations and X-ray data showed that Al4C3 was formed at the graphite/melt interface up to the addition of 10 mass%Si, and that SiC was formed by the Al-20 mass%Si melt during the holding. The phenomenon was caused by the energy change at the graphite/melt interface when the graphite reacted with the melt.
The contact angle (θ) of graphite/aluminum calculated from the adhesive tension measured with the Meniscography became smaller than that with the sessile drop method at the third stage. The difference in θ was caused by the presence of an oxide film of the melt which inhibited the melt spreading. The oxide film formed over the meniscus was found to delay the stating time of spread by wetting in the Meniscographic examination.View full abstractDownload PDF (2233K) -
Tadashi Ariga, Masamori Iida, Tateo Kurosu, Yasuo Miyamoto, Keitaro Ko ...1990 Volume 54 Issue 7 Pages 847-852
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of heat treatment of electron-beam deposited W films on SiO2/Si was investigated by means of electrical resistivity, structure and W/SiO2 interface reaction. The W source material selected was grade 99.999% pure. W films (800-1150 nm) were deposited at the substrate temperatures 623 and 823 K and different vapor deposition rates. The typical pressure during the evaporation was 10−4 Pa. The W films was annealed in a vacuum at temperatures between 973 and 1273 K for 3.6 ks.
Columnar structure was observed at the cross-section of the deposited W films. The electrical resistivity of the W films was four times higher than that of bulk. The electrical resistivity depended upon the substrate temperature and vapor deposition rate. The electrical resistivity decreased with growing grain by the heat treatment. The films by the heat treatment at 1173 K shows the electrical resistivity similar to that of bulk. SiO2 films were not changed by the heat treatment at 1273 K but Si was diffused to the surface of W films.View full abstractDownload PDF (1355K)
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