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Volume 53, Issue 7
Displaying 1-16 of 16 articles from this issue
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Tetsurou Abe, Takeshi Araki, Kazuhide Tanaka1989 Volume 53 Issue 7 Pages 635-642
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThermal desorption spectra (TDS) of hydrogen dissolved in amorphous Fe-Ti and Ni-Zr alloys have been measured. Each spectrum presents, below the crystallizing temperature TX, a broad maximum which continually shifts toward lower temperatures with increasing initial hydrogen concentrations. This maximum usually consists of a few peak components which originate from the desorption of hydrogen atoms occupying nonequivalent sites in the amorphous alloy. An atempt was made to simulate the TDS spectra by employing a surface recombination model in which the desorption rate is controlled by the reaction H+H→H2 at the surface. Assuming that the site energy distribution function, N(E), for the dissolved H atoms is given by a combination of a few Gaussians, the TDS has been calculated and compared with the observed spectrum. With a proper choice of the Gaussian parameters, a good fit was obtained between the simulation and the experiment. The physical meaning of N(E) involving the plural Gaussian distributions is discussed.View full abstractDownload PDF (1073K) -
Toshiyuki Koyama, Toru Miyazaki1989 Volume 53 Issue 7 Pages 643-650
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt is considered that the free energy of the microstructure ought to be evaluated as the set of many precipitate particles. In the present work, a new method to estimate the total free energy of the microstructure containing a chemical free energy, an elastic strain energy, an interfacial energy and so on was proposed, and then a possibility of prediction to the microstructure development was discussed on the basis of the free energy evaluated. The results obtained are as follows: (1) The interfacial energy of the microstructure vaties in parabola with the volume fraction of precipitates f. (2) The sequence of microstructure development during ageing can be predicted by comprehensive evaluations on the free energies of the various modes of microstructure.View full abstractDownload PDF (1194K) -
Toshiyuki Koyama, Toru Miyazaki, Minoru Doi1989 Volume 53 Issue 7 Pages 651-657
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe development of the microstructure arising from the phase decomposition in the materials has been inferred from the equilibrium phase diagram. However, the equilibrium phase diagram does not give any information on the process of phase transformation. In the present work, we newly propose a Time-Temperature-Composition diagram, which is named as a T-t-c system diagram. By using the system diagram the sequense of phase transformation and the microstructural development with progress of ageing can be comprehensively described.View full abstractDownload PDF (1050K) -
Akira Tahara, Kiyoshi Kuruma, Yasunori Hayashi1989 Volume 53 Issue 7 Pages 658-663
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe Permeation response of hydrogen through palladium coated iron specimens by an electrochemical oscillating method was studied to elucidate the behavior of hydrogen at the Pd-Fe interface. The Frequency dependence of the phase lag between the osicillating cathodic current and the oscillating anodic current was measured: the cathodic current means the rate of the hydrogen charging, and the anodic current the rate of the hydrogen permeation.
The phase lag of the Pd-coated Fe specimen was larger than that of the non-coated Fe specimen. This excess of the phase lag was due to the diffusion of hydrogen through Pd film and to the reaction at the Pd-Fe interface.
The boundary conditions at the Pd-Fe interface were proposed as
(This article is not displayable. Please see full text pdf.)
\ oindentwhere JPd and JFe mean the hydrogen fluxes in the Pd and Fe phases, respectively, and CPd and CFe are the concentrations of hydrogen in both phases, h and k being the kinetic parameters. The frequency dependence of the phase lag measured was explained reasonably under these boundary conditions.View full abstractDownload PDF (777K) -
Masahiko Ikeda, Shin-ya Komatsu, Takashi Sugimoto, Kiyoshi Kamei1989 Volume 53 Issue 7 Pages 664-671
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSOn Ti-20∼40%Nb alloys quenched from 1073 K, the changes in resistivity and its temperature dependence during the early stage of aging at low temperatures were related to phase transformations confirmed by X-ray diffraction. The following results were obtained:
(1) 26-40%Nb alloys tended to approach a negative temperature dependence (NTD) of resistivity, which was attributed to reverse transformation of α″ orthorhombic martensite confirmed in 26-35%Nb alloys.
(2) An isothermal reverse transformation of α″ continued for a long period by 473 K aging of the 35%Nb alloys.
(3) As and/or Af temperatures of α″ were distinguished from the starting temperatures of athermal ω formation by reversibility of the resistivity change with cooling or heating of specimens and by the direction change of resistivity-temperature coefficients.
(4) As and Af of α″ formed by quenching were lowered with increasing Nb content and were estimated to be 620 and 720 K in 26%Nb, 550 K and 610 K in 30%Nb, 450 and 500 K in 35%Nb, 400 and 450 K in 40%Nb, respectively.
(5) Above the Af, the β phase formed by a perfect reverse transformation of α″ decomposed to α+β phases with diffusion. Long-period heating at a temperature slightly below the As resulted in a direct decomposition of α″ to β+α.View full abstractDownload PDF (1050K) -
Dong Zhilli, Atsushi Sekiya, Wataru Fujitani, Shigenori Hori1989 Volume 53 Issue 7 Pages 672-677
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCu-Zr aged alloys are very interesting as high strength and high electrical conductivity alloys. The precipitation and electrical conductivity change during aging of Cu-Zr binary and Cu-Zr-Si ternary alloys were investigated by means of hardness and electrical resistance measurements and structure observations.
Decomposition of the Cu-Zr super-saturated solid solution during aging occurs by forming a plate-like stable phase with cubic crystal structure. The plate-like precipitates are preferentially precipitate in the grain boundary and so the precipitate free zones about 1 μm in width are formed.
The addition of 0.1∼0.3 mass%Si eliminated the precipitate free zone near the grain boundary and the Cu-Zr-Si ternary fine precipitate within a grain are coarsened slowly during high temperature holding. Thus, the addition of Si to the Cu-Zr binary alloy contributes simultaneously to the retardation of decreasing hardness at high temperature and the improvement of heat resistance.View full abstractDownload PDF (1249K) -
Katuo Saitou, Junji Kihara, Yasuo Otoguro1989 Volume 53 Issue 7 Pages 678-684
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt has been clarified in a previous report that in the case of high machine-stiffness, the stress drop and time interval increase with increasing spring constant ratio α. However, it is unknown whether such a dependence may apply to low-stiffness machine systems. The purpose of this report is to clarify the influence of the stiffness on the plastic elongation and stress drop in the discontinuous deformation using 7075-Al alloy and to discuss it together with the previous results obtained using a high-stiffness machine.
The method to lower the stiffness of the testing machine is to insert a spring between the load cell and the specimen grip. The cross head speed was selected so that the plastic strain rate approximately may equal 3×10−5 s−1. Tensile tests were performed at 303 K.
It was found that the form of the stress-strain curve changed from a periodical to a stepped one as the stiffness is decreased. The stress drop showed a peak at a certain α while the plastic elongation increased monotonously with increasing α. The plastic elongation tended to saturate for large α especially at low strain. The stress drop for large α had a negative value and this was explained in terms of the plastic instability of local deformation of the specimen.View full abstractDownload PDF (842K) -
Tadahisa Matsushima, Kazuo Saito, Atsushi Takei, Akira Ishida1989 Volume 53 Issue 7 Pages 685-691
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTi-Al films with various compositions were prepared by the ion plating method. Compositions of the films were controlled by selecting the experimental conditions of ion plating. The properties of films, such as the homogeneity of composition, structural phases and microhardness, were investigated by Auger electron spectroscopy, X-ray diffraction and hardness measurements.
It was found that the hardness of the as-deposited films showed a maximum at the stoichiometric composition of 50 at%Al and its composition dependence was similar to that of a rapidly solidificated bulk alloy. The films were implanted with 150 keV nitrogen ion N2+ at room temperature to doses from 2×1021 to 1.7×1022 ions/m2. After the nitrogen ion implantation the hardness of the films increased about 2-3 times that of the unimplanted state and its composition dependence changed to exhibit a minimum at the stoichiometric composition of 50 at%Al. The maximum concentration of implanted nitrogen in the Ti-rich films reached about 50 at%, and decreased to 30% for the Al-rich films. In the nitrogen implanted films, nitrides such as AlN and Ti2N were formed and neither TiN nor Ti2AlN were observed. Corrosion resistance of the films was improved markedly by a nitrogen dose of more than 2×1021 ions/m2.View full abstractDownload PDF (2230K) -
Toshio Oishi, Keita Nakagawa, Katsutoshi Ono1989 Volume 53 Issue 7 Pages 692-697
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe corrosion resistance tests of Cu-Fe-O oxide melts equilibrated with Cu-Fe liquid alloys were made for various refractory materials in the temperature range 1773-1873 K. High purity magnesia showed a best corrosion resistance among the refractories tested.
Using the high purity magnesia as the crucible, the oxygen potential measurements of the two-phase equilibria between Cu-Fe-O oxide melts and Cu-Fe liquid alloys were made at 1773 K by means of a solid electrolyte galvanic cell technique. The following cell was used:
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The isothermal section of the Cu-Fe-O system at 1773 K was drawn from the oxygen potentials measured and the analysed values of the components of both phases. Alloy-oxide two phase region covered a wide area in the Cu-Fe-O phase triangle and the equilibrium oxygen partial pressure changed between 10−4 and 100 Pa in this region. Copper contents in the oxide melts in equilibrium with liquid alloys were below 2 mol% for the iron concentrations above 2.5 mol% in the Cu-Fe alloys. The solubility of oxygen in the Cu-Fe alloy showed a minimum of about 0.01 mass% at the iron concentration of around 2 mol%.View full abstractDownload PDF (898K) -
Toshiaki Sekine, Naruhiko Nakanishi, Eiichi Kato1989 Volume 53 Issue 7 Pages 698-703
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSExperimental rate data on the chemical vapor deposition of boron by reduction of boron trichloride with hydrogen are analyzed to determine the reaction mechanism. The experiments were conducted at atmospheric pressure. Tungsten was used as the substrate. It has been found that deposited film is WB. The region of mass transport control could be separated from that of chemical reaction control; in the former the mass increase of the sample depends on the total flow rate of the gas, and in the latter the mass increase does not. The activation energies in the higher temperature range and in the lower temperature range have been determined to be 17.1 and 127.9 kJ/mol, respectively. The values of activation energies also indicate that the reaction is controlled by mass transport at higher temperatures. When mass transport limitation is absent, the reaction orders with respect to boron trichloride and hydrogen are one-third and one-half, respectively. By comparing these orders with those obtained from Langmuir-Hinshelwood type equations, the rate controlling mechanism has been identified to be the desorption of hydrogen chloride from the substrate.View full abstractDownload PDF (594K) -
Yoshio Fujishima1989 Volume 53 Issue 7 Pages 704-710
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA study was made to reveal the relation between the hydrogen evolution on and entry into nickel in an aqueous solution of 100 mol·m−3 sulfuric acid using an electrochemical technique.
Nickel foils were electrolytically charged with hydrogen kept at uniform concentrations in the ranges of hydrogen overpotentials 0.1-0.3 V and temperatures 298-343 K. The rates of hydrogen desorption from the hydrogen-charged foils were measured, immediately after the palladium plating following the cathodic charging, at a potential of 0.1 V against a saturated calomel electrode in an aqueous solution of 100 mol·m−3 sodium hydroxide at different temperatures ranging from 276.5 to 343 K. The diffusivity and solubility coefficients for hydrogen in nickel were calculated from the hydrogen desorption rate-time curves, and the values of hydrogen fugacity in conceptual cavities immediately below the cathodic surfaces were obtained from the solubility coefficients by using Sieverts’ law.
The internal hydrogen fugacity, fH2, of the cathodic surface is expressed experimentally as follows:
(This article is not displayable. Please see full text pdf.)
\ oindentwhere η is the hydrogen overpotential, F the Faraday constant, R the gas constant, and T the absolute temperature. It seems that the hydrogen solubility at the reversible hydrogen potential is equivalent to that existing in equilibrium with a hydrogen fugacity of 101 kPa. The heat of solution of hydrogen for nickel changes by (0.655±0.003)ηF with hydrogen overpotential.View full abstractDownload PDF (779K) -
Ryuji Watanabe, Hisashi Andoh, Kiyoji Iwashita, Yukio Kurosawa1989 Volume 53 Issue 7 Pages 711-715
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSVarious electrode materials for low surge vacuum circuit breakers which were impregnated with Ag2Se intermetallic compound into sintered Co matrix were prepared in vacuum.
The microstructures and basic electrical properties for the electrodes have been examined. Ag2Se can be impregnated to the Co matrix very well. There are almost no structural defects in these alloys.
The maximum chopping-current value of the materials are approximately 1∼1.2 A and the average are 0.4 A. Especially, the chopping-currents of the electrodes are very stable and at a low level even after interruptions.
Further, it has been found that the materials have are comparable in performance to the conventional electrode of Cu-0.75 mass%Pb alloy in withstand-voltage and interruption-ability.View full abstractDownload PDF (1470K) -
Tokuhiko Nishida, Masao Yamamiya, Susumu Chida1989 Volume 53 Issue 7 Pages 716-722
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of addition of 20%Fe-70%Ni-10%B master alloy powder on the sintering behavior, microstructure and mechanical properties of atomized iron powder compacts has been studied.
The results are summarized as follows.
(1) The Fe-Ni-B master alloy profoundly activated the sintering process through the formation of eutectic liquid. Rapid densification occurred above 1403 K. Densities of the order 99% theoretical were readily achieved with 2% addition.
(2) Sintered strength increased with the amount of master alloy powder. With 5% additive, the tensile strength of 400 MPa was obtained. Maximum elongation of 33% occurred at 2% addition.
(3) Elongation was closely related to the eutectic phase and decreased as the brittle intermetallic phase became continuous.
(4) The sintering process of this work could be treated as traditional persistent liquid phase sintering. The volume fraction of liquid necessary for full density was 8%.View full abstractDownload PDF (2041K) -
Koji Hayashi, Hiroyuki Eto, Hiroshi Kihara1989 Volume 53 Issue 7 Pages 723-728
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe green compacts of Fe+(25-80)%Co and Fe+(25-75)%Ni mixed ultrafine metal powders (average particle size of Fe, Co and Ni each powder, 0.02 μm) were mainly pressure-sintered under 100-500 MPa for 3.6 ks in H2 gas, after the reduction of the oxide. The lowest temperature for complete densification (Tsc), the average crystal grain size and hardness (HV) of the sintered compacts were investigated, compared with the results on Fe, Co and Ni single component powders.
The results obtained were as follows: (1) The Tsc under 500 MPa for Fe+50 at%Co and Fe+50 at%Ni mixed powder compacts were about 700 and 680 K respectively, which were higher by 100-210 K than those for single component powder compacts. (2) The minimum of the average crystal grain size of the nearly dense compacts, which were sintered at 640 K under 500 MPa, were about 0.12 μm at 50 at%Co and 0.11 μm at 25 at%Ni respectively. These were smaller by about 0.03-0.14 μm than those of single component compacts obtained under the same condition. (3) The highest hardness of the Fe-Co and Fe-Ni sintered compacts were about 870 HV at 50 at%Co and 730 HV at 25 at%Ni, which were higher by 100-200 HV than those of single component compacts at the same crystal grain size and higher by about 600-700 HV than those of usual coarse-grained metals. The Hall-Petch linear relationship was observed to hold for the hardness of Fe-50 at%Co and Fe-50 at%Ni single phase compacts.View full abstractDownload PDF (1149K) -
Tomoki Tomita, Yasuyuki Takatani, Genzo Hashizume, Yoshio Harada1989 Volume 53 Issue 7 Pages 729-734
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to develop materials having corrosion resistance and wear resistance, NbC dispersed overlay weld alloys were formed on mild steel by a plasma powder welding process using mixed powders of NbC and Ni-50 mass%Cr alloy. The microstructure and hardness of these overlay weld alloys were studied by using SEM, TEM, EPMA and the hardness tester.
The matrix was contaminated by a large amount of Fe from mild steel and became the γ-phase, Fe(Ni, Cr) solid solution. Most of NbC was dispersed nearly uniformly as unmelted particles in the matrix alloy. A part of NbC was melted in the molten pool, and during solidification primary NbC, eutectic (γ+NbC) and eutectic (γ+NbC+M23C6) appeared.
With increasing mixing ratio of NbC, the hardness of the overlay weld alloys increased and reached HV370 at 60 mass%NbC.
The solidification process of the matrix alloy and the effects of the solidification structure on hardness were discussed by observation of the morphology and distribution of carbides.View full abstractDownload PDF (1650K) -
Tomoo Takayama, Shojiro Ochiai, Kozo Osamura1989 Volume 53 Issue 7 Pages 735-743
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt is known that the critical current density of Ba2YCu3O6+x superconductors made by the solid state reaction method is much lower than that of conventional metallic superconductors. Recently, there has been considerable interest drawn to the improvement of the critical current density for their practical applications. In this report, we investigated the factors which enhance the critical current density of the Ag sheathed tape prepared by powder in tube method.
The composite consisting of the calcined powder sheathed with the Ag tube was cold-rolled or pressed to form a tape and then sintered. In the case of the Ag-sheathed composites, crack generates during a heat-treatment because of thermal stress due to a distinction of thermal expansion coefficient between oxide and Ag sheath. In a part of experiments, the calcined powder was reduced to a partially metallic mixture by hydrogen gas in order to eliminate the generation of cracks. The critical current density and the microstructure have been investigated.
The usage of the hydrogen gas reduced powder was effective for eliminating a serious degradation of the critical current density for the thin tape specimens. The critical current density tended to increase with decreasing tape thickness. The improvement was attributed to the formation of textured structure and densification. From the analysis of the pole figure and the observation of the microstructure, the c axis of grains was deduced to incline by about 10 degrees to the tape surface normal. The pressing technique was found to be more effective for improving the critical current density than the cold-rolling. The present investigation confirmed that the higher critical current density can be obtained for the thinner tape prepared by the pressing technique.View full abstractDownload PDF (2363K)
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