All issues
Volume 51, Issue 5
Displaying 1-14 of 14 articles from this issue
- |<
- <
- 1
- >
- >|
-
Hisashi Kuwano, Kiyohiro Iioka, Yoshikazu Hamaguchi1987 Volume 51 Issue 5 Pages 385-389
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe internal field of iron nucleus in iron-chromium alloys has been measured by Mössbauer spectroscopy to clarify a change in the matrix concentration attended by the spinodal decomposition during aging at 748 K. The internal field change is analyzed by the Johnson-Mehl equation. The spinodal mechanism is characterized by four steps of time evolution of the compositional fluctuation, which is distinguished from the nucleation-growth process in the lower Cr content alloys. A Cr-rich precipitate is formed at the end of the third stage of the spinodal decomposition followed by the coalescence by a mechanism similar to the Ostwald ripening in the fourth stage.View full abstractDownload PDF (692K) -
Kazushige Tokuno, Sadakichi Kitajima, Yuzo Nakamura, Chiken Kinoshita, ...1987 Volume 51 Issue 5 Pages 390-399
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMacroscopic and microscopic inhomogeneities in plastic deformation of quenched aluminum single crystals and polycrystals were examined by observing slip bands and dislocation structures using optical and transmission electron microscopes to make clear the enhancement of heterogeneous deformation in FCC metals due to the introduction of a large number of small dislocation loops. Main results are as follows: Both secondary and primary slip bands in single crystals appear heterogeneously along the length of crystals both in macroscopic and microscopic scales. Primary edge dislocations of the same sign are distributed in excess in coarse primary slip bands. Secondary slip banbs are initiated from a point of a primary slip band and then extend into a definite direction, and dislocation structures indicating one-directional extension of multiplied secondary dislocations are observed. Secondary dislocations protruding into an area between coarse primary slip bands from coarse primary slip bands sweep away dislocation loops existing there. Shear displacement in a conjugate slip band corresponds to that expected in compressive deformation, in spite of tensile deformation. The decrease in uniform elongation is recognized to occur in quenched polycrystals.
The inhomogeneous formation and unusual behavior of secondary silps are attributed to the constraint of deformation due to grips in single crystals and due to neighbouring grains in polycrystals. The ductility loss in metals containing a large number of small dislocation loops is discussed on the basis of the present results.View full abstractDownload PDF (3317K) -
Seiji Miura, Shouichi Ochiai, Yoshihiro Oya, Yoshinao Mishima, Tomoo S ...1987 Volume 51 Issue 5 Pages 400-406
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSingle crystals of Ni3(Al, Ti) with selected orientations were deformed in compression at temperatures between 77 K and 1223 K with strain rates varying from 1.4×10−5 to 1.4×10−2 s−1, in order to investigate the effect of strain rate on the flow stress. Results obtained are as follows: In the intermediate temperature range where the strength increases anomalously with increasing temperature, the strain rate dependence of flow stress is very weak. This phenomenon is likely to be characteristic of intermetallic compounds with L12 structure which show positive temperature dependence of strength. On the other hand, in the higher temperature range where the flow stress decreases gradually and {100} slip occurs predominantly, the strength is very sensitive to the strain rate and shows a normal strain rate dependence. Judging from the magnitudes of activation energy and activation volume for higher temperature deformation, it is concluded that {100} slip is controlled by the Peierls-Nabarro mechanism. Equations to relate flow stress and strain rate for {100} slip are derived, and they well account for the experimental results at all strain rates tested.View full abstractDownload PDF (1005K) -
Yutaka Hiraoka, Masatoshi Okada, Hirosada Irie, Tadayuki Fujii1987 Volume 51 Issue 5 Pages 407-412
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe purpose of this study is to investigate the macro- and microstructures and the tensile properties of electron-beam-welded single crystals of molybdenum. The single-crystal sheets were prepared by means of secondary recrystallization. The welding was carried out by a melt-run technique.
The weld metal had the same crystallographic orientation as the base metal, and no grain boundary was observed. However, many large weld pores were formed mostly along the weld bond. The strength and ductility of the welded joints of single crystals were almost the same as those of the base metal (“annealed” single crystals). It is concluded that the joint efficiency of molybdenum single crystals at room temperature or above was excellent and nearly 100%.View full abstractDownload PDF (1748K) -
Keisuke Ishikawa, Toshio Ogata, Kotobu Nagai, Tetsumi Yuri1987 Volume 51 Issue 5 Pages 413-418
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSWe have examined the effect of strain rate on the tensile behavior of austenitic stainless steels in liquid helium. We observed similar flow curves of the materials in He I as well as He II. We also measured some temperature rise of the specimens during tensile deformation. The serrated deformation was associated with the temperature rise and was dependent on the strain rate.
It is presumed that the transition from discontinuous deformation to smooth one corresponds to the traisition of heat transfer behavior between the specimen surface and the surrounding liquid helium.
It is found that the martensitic transformation of austenitic stainless steels has conspicuous influence on the tensile behavios and the temperature rise of the specimens.View full abstractDownload PDF (784K) -
Masanobu Matsumura, Yoshinori Oka, Toshihiko Odohira, Ryuichiro Ebara, ...1987 Volume 51 Issue 5 Pages 419-424
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCavitation erosion tests to steels coated with TiN layer by physical vapor deposition were conducted by using a wall-facing vibratory testing facility. In this facility a stationary specimen was held with a narrow gap (0.4 mm) against a vibrating horn by which the cavitation was generated over the specimen surface. The erosion damage on the test specimens was evaluated by various methods, and it has been confirmed that the erosion resistance of TiN-coated steel is superior to steel coated with Cr of the same film thickness by electroplating, of course to base metal (SUS410J1 stainless steel) not coated. The causes of this improvement in the erosion resistance of TiN coated materials were elucidated as follows: Firstly the TiN layer do not peel off from the substrate surface owing to its enough adhesion. Secondly the erosion resistance of the layer itself is more excellent than that of the substrate material. In addition, it has been also confirmed that the excellent erosion resistance is kept even after the damage has reached the substrate material, since the residual stress generated by the layer deposition improves the durability of base metal.View full abstractDownload PDF (1430K) -
Akito Yoshida1987 Volume 51 Issue 5 Pages 425-431
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSeveral microscopic dimensionless numbers have been devised by extrapolating microscopic dimensionless numbers to atomic scale. These microscopic dimensionless numbers show a nearly constant value for most metals, and then the following equations have been obtained for expressing some physical quantities of liquid metals. The surface tension is given by γ=0.86×10−7 TmV−2⁄3θ−0.81, where Tm, V and θ are the melting temperature in K, the atomic volume in m3/mol and the reduction temperature, respectively. The coefficient of viscosity is expressed in the form of η=4.87×10−4V1⁄6(ργθ0.63)1⁄2, where ρ is the density in kg/m3. The self-diffusion coefficient is also given by D=6.2×10−3η⁄ρ.View full abstractDownload PDF (762K) -
Masao Iwai, Noriko Okui, Koichi Arai, Toshio Izaki, Yasuhiro Awakura, ...1987 Volume 51 Issue 5 Pages 432-438
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe feasibility of the hydrometallurgical treatment of mixed ore of Mn-nodule and nickel sulfide by using the oxidative-reductive leaching method was investigated from a thermodynamic and a kinetic aspect based on experimental results of the leaching rate, the stoichiometry of the leaching reaction and the determination of the rest potentials of the samples.
The experimental results are summarized as follows:
(1) The oxidative leaching rate of NiS and the reductive leaching rate of MnO2 from a mixture of NiS and MnO2 increase with the concentration of HCl and the temperature of the solution. However, the leaching rates are independent of the agitation of the solution. The leaching of Ni and Mn ions from the mixture of NiS and MnO2 increases with the molar ratio of NiS/MnO2.
(2) The reductive leaching rate of Mn-nodule from a mixture of Mn-nodule and Ni3S2 is larger than that of a mixture of Mn-nodule and NiS.
(3) The oxidative leaching reaction of nickel sulfide is a simultaneous one of the formation of sulfate ion and elemental sulfur.
(4) From the thermodynamical consideration and the experimental studies, it is concluded that the new hydrometallurgical treatment process for Mn-nodule by using the oxidative-reductive leaching method is available.View full abstractDownload PDF (1022K) -
Toshio Shimoo, Shigeru Ando, Hiroshi Kimura1987 Volume 51 Issue 5 Pages 439-445
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe rates and mechanism of the reduction of chromium oxide slags by solid carbon have been investigated at temperatures between 1773 and 1973 K in the concentrations of Cr2O3 ranging from 10 to 50% with the slag basicity CaO/SiO2 taking values from 0.5 to 1.4. The rate of reduction has been determined from the mass loss measured by means of thermogravimetry under argon atmosphere.
The acceleration of the reduction of Cr2O3 at an early stage is caused by an increase in the contact area of the slag with the graphite. In some reduction curves of acid slags, a long incubation period is observed. In the range of reduction from 30 to 70%, the rate of reduction is essentially indepedent of the concentration of Cr2O3. The slag wets well the graphite and hence the reduction proceeds rapidly in the region of two-liquid-phase in the CaO-SiO2-Cr2O3 system. The changes in wetting of the graphite surface by the molten slag complicate the temperature dependence of the reduction rate.View full abstractDownload PDF (1317K) -
Li-Wei Zhang, Masahiro Susa, Kazuhiro S. Goto1987 Volume 51 Issue 5 Pages 446-451
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe evaporation and condensation mechanism of a super-ionic conductor, Li2O-B2O3 binary system, has been studied.
The thin oxide films were synthesized in the amorphous state on glass substrates with the use of conventional vacuum-deposition method under the vacuum condition of about 7×10−3 Pa. The compositions of source materials were 3Li2O·2B2O3, Li2O·B2O3, and Li2O-2B2O3. The source- and the substrate-temperature were mostly 1123 K and 373 K, respectively. The typical thickness of the thin films was around 1 μm.
In order to estimate the vapor species in this deposition process of thin oxide films, the following have been especially investigated:
(1) The relation between the compositions of evaporation sources and thin films, (2) the dependence of thin-film composition on the source temperature, (3) the dependence of thin-film composition on the substrate temperature and (4) the dependence of deposition rate on the substrate temperature.
The results are as follows;
(1) For XLi2O(Li2O mole fraction in the source) <0.5, the composition of oxide film is independent of the source composition, but for XLi2O>0.5, the Li2O concentration in the film becomes larger with increasing Li2O concentration in the source.
(2) The composition of the thin film is independent of the source temperature.
(3) The composition of the thin film is dependent on the substrate temperature, and its Li2O concentration becomes larger with decreasing substrate temperature.
(4) The deposition rate is increased with lowering substrate temperature.
From the above results it has been inferred that the vapor species is predominantly LiBO2. The thermodynamics and the kinetic theories of gases have been used for the estimation.View full abstractDownload PDF (790K) -
Hideaki Itoh, Takatoshi Ogawa, Keizou Ohnishi1987 Volume 51 Issue 5 Pages 452-457
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe additional effects of Mm and Al on the hydrogen desorption properties of CaNi5 were studied from hydrogen absorption-desorption cycles in hydrogen containing 300 ppm O2. It turned out that the hydrogen discharge ratio of Ca1−xMmxNi5−yAlx(x=0, 0.3 and y=0, 0.1) alloys decreased in the early cycles, but after that it gradually increased because of the self-restoring mechanism for the degradation of hydrogen discharge ratio. The self-restoration was slower in the case of the addition of both Mm and Al than in the case of the addition of Mm only.
Auger electron spectroscopy revealed that the content of Ca increased in the surface of allays exposed to 1200 Pa O2. The addition of Al caused the structure just under the Ca-rich layer to be poor in Ca content.View full abstractDownload PDF (832K) -
Koichiro Morimoto, Muneaki Watanabe, Takuo Takeshita1987 Volume 51 Issue 5 Pages 458-464
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt is now well established that the addition of Zr and/or Hf increases the coercive force of the Sm2Co17 type magnets. The coercive force of this type magnets is due to the domain wall pinning mechanism, and it is industrially important to improve the squareness of the hysteresis loop in order to minimize the magnetizing field. In this study, influences of aging treatments of Sm(Co0.67Fe0.21Cu0.08Ni0.02Zr0.02)7.6 magnets were investigated with regard to the coercive force and the shape of the hysteresis loop. Results obtained are as follows; the continuous cooling, which is well known as a standard aging treatment for producing a high coercive force in the Sm2Co17 type magnets, increases the intrinsic coercive force, as the starting temperature of continuous cooling is raised in the range of 1103-1173 K. However, the squareness of the hysteresis loop becomes poorer, if the intrinsic coercive force of magnets was increased to a higher value than 520 kA·m−1 by this treatment. On the contrary, we found that a repeated continuous cooling from lower starting temperatures (i.e. 1053-1073 K) induced a high coercive force in this material with a good square hysteresis loop making it easier to be magnetized. For instance, a magnet which possesses an intrinsic coercive force of 820 kA·m−1 and a maximum energy product of 223 kJ·m−3 can be obtained by three cycles of continuous cooling from 1053 K, and it can be magnetized almost fully with a field less than 1600 kA·m−1. We also observed that a cycle-aged magnet has a finer two-phase structure consisting of the 2-17 phase and the 1-5 phase as compared with a single-aged magnet of about the same intrinsic coercive force.View full abstractDownload PDF (1218K) -
Hiroaki Kumakura, Kazumasa Togano, Susumu Tsukamoto, Hirosada Irie, Ky ...1987 Volume 51 Issue 5 Pages 465-471
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSNb3Al and Nb3(Al, Ge) composite tapes with excellent superconducting properties were fabricated by the continuous electron beam irradiation method. Nb-25 at%Al and Nb-20 at%Al-5 at%Ge tapes were prepared by the powder metallurgy process using Nb-sheath. Electron beam irradiation was applied to the tape surface in a vacuum at a tape velocity of 6 m/min. The acceleration voltage, current and diameter of the electron beam were 20 kV, 5-30 mA and 0.5-3 mm, respectively. As the power density was high and the irradiation time was short, the tapes were heated and cooled much faster than a tape heat-treated by a conventional method. As a result stoichiometric A-15Nb3Al and Nb3(Al, Ge) compounds were formed without any excess grain coarsening. Tc of the as-irradiated tape was 16-18 K, which was increased by ∼2 K by a subsequent annealing at 973 K for 360 ks (100 h). The maximum Tc(onset) values obtained were 18.5 K for the Nb-Al tape and 20.2 K for the Nb-Al-Ge tape. Jc increases with increasing power density until the melting occurs and then rapidly decreases at higher power densities, due to the decrease of A-15 volume fraction. The Nb-Al and Nb-Al-Ge tapes processed under proper conditions show excellent Jc-H properties. Jc exceeds 108 A/m2 in the fields up to 25 Tesla for Nb-Al and up to 30 Tesla for Nb-Al-Ge. Jc of Nb-Al-Ge is the largest one so far obtained in the superconducting materials at ∼30 T. The large Jc values in the fields, as well as the easy scale-up procedure, indicate that the continuous electron beam irradiation method is promising for the fabrication of advanced superconductors, e.g. Nb3Al and Nb3(Al, Ge) capable of generating fields over 20 Tesla.View full abstractDownload PDF (1254K) -
Naoji Nakamura, Hakaru Masumoto1987 Volume 51 Issue 5 Pages 472-478
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSInvestigation has been made into the electrical resistivity ρT and its mean temperature coefficient Cf at temperatures from 293 to 373 K, the electrical resistance at elevated temperatures from room temperature to 1073 K, and the melting point for Cu-0-75 at%Mn-0-50 at%Al alloys in the air-quenched state. The alloys show a complicated variation near ρ293 at 293 K with Mn and Al concentrations, respectively. Generally, ρ293 in the composition in 25 at%Al shows a lower value. To be more specific, its value increases slightly at first and monotonously after showing a minimum value lower than 0.3 μΩ·m at 20-31 at%Mn with increasing Mn concentration, and then reaches the highest value of 2.0 μΩ·m at 70 at%Mn. On the other hand, Cf at 293-373 K shows a maximum value higher than 5000×10−6 K−1 near the composition of ρ293 minimum, and contours of equivalent values of Cf take the form of a long elliptical shape which expands with the Mn concentration.
When the temperature is elevated, the electrical resistance Δρ⁄ρ273 vs. temperature T curves of the Cu-Mn-25 at%Al alloys show a very complex change with the Mn concentration. In general, the heating and cooling curves do not agree with each other. However, near the composition of 25 at%Mn, the Δρ⁄ρ273−T heating curve agrees well with the cooling curve at a temperature lower than the magnetic transformation point. This appears to be due to the reason that the electrical properties of the (αCu+T3+γ) and (γ+T3+βMn) phases which exist in the lower temperature range are balanced.
When quenched in air at the cooling rate of 1.75 K·s−1 after heating at 1073 K for 3.6 ks, a Cu-22.5 at%Mn-25.0 at%Al alloy exhibits ρ273 and Cf of 0.26 μΩ·m and 4100×10−6 K−1, respectively, and its product ρ·Cf is 1066 pΩ·mK−1 which is 2.7 times as large as that of the practical element material being used for temperature sensors. In addition, this alloy has many advantages as follows: The linearity of electrical resistance at temperatures lower than 400 K is good; the electrical properties are scarecely changed after heating for a long period less than 100 ks; the melting point is as low as 1200 K; the material is inexpensive.
Except for their poor antioxidation and non-workability, the alloy is a very promising element material for use in low-temperature sensors of a relatively low temperature range.View full abstractDownload PDF (1013K)
- |<
- <
- 1
- >
- >|