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Volume 55, Issue 3
Displaying 1-18 of 18 articles from this issue
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Tokushi Kizuka, Hideki Ichinose, Yoichi Ishida1991 Volume 55 Issue 3 Pages 233-240
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAtomic structure of grain boundaries in nanocrystalline silver was investigated by high resolution electron microscopy. Nanocrystalline silver was prepared by compacting ultrafine particles produced by gas condensation technique at mechanical pressures of 250 MPa and 2 GPa in a vacuum of 10−6 Pa. Isochronal annealing was performed in the temperature range from ambient temperature to 1073 K. Vickers microhardness was also measured for samples which were compacted from 250 MPa to 2 GPa and annealed isochronally increasing the temperature.
Coherent twin boundary was dominant in as-compacted nanocrystalline silver. Voids from 3 to 5 nm in size were observed not in the grain but on the grain boundary especially at the grain boundary triple point. Microstructural difference between the specimens compacted at 500 MPa and 2 GPa was small. However, the surface defects of the order of 1 μm in size decreased with increasing compacting pressure. Vickers microhardness (Hv) of as-compacted speciemens increased with compacting pressure. The Hv decreased rapidly with an increase in temperature to about 473 K. Grain coarsening started upon heating. The grain shape was mostly isotropic with a diameter of 20-50 nm and occasionally elongated 100-300 nm when twins were aligned. The average grain diameter of the specimen, however, remained below 1 μm even up to 1073 K.View full abstractDownload PDF (3193K) -
Teiko Okazaki, Ryôfu Miyasawa, Singo Takami1991 Volume 55 Issue 3 Pages 241-247
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe magnetization and the magnetocaloric effect of eight Ni-Mn alloys containing 66-83 at%Ni have been investigated in connection with Ni content.
In those alloys annealed for a relatively short time, the measurements were made in the temperature range extending over some hundred degrees above and below room temperature. The curves indicating the temperature-dependence of saturation magnetization in six alloys containing 71-83 at%Ni showed trends approximately similar to those of the ferromagnetic 3d transition elements. From such a trend curve it was possible to evaluate roughly the ferromagnetic Curie temperature, TF, but it was known that the precise evaluation of TF was more difficult in those alloys than in the 3d transition elements. Then, for those six alloys the values of spontaneous magnetization in the temperature range near TF were derived from the experimental results of the magnetocaloric effect, and the values of TF were determined.
The curves showing the relation between the relative spontaneous magnetization and the reduced temperature, derived from the above-mentioned results for those six alloys, almost agreed with each other. Consequently, the law of corresponding states holds for those alloys. In addition, the curve indicating this law fits on the whole the theoretical curve derived from the Brillouin function whose total angular momentum quantum number is 5/2. On the basis of the results described above, the values of the coefficient of Weiss molecular field at TF and the strength of molecular field at 0 K were calculated for those six alloys. It was also shown that those values varied systematically with increasing Ni content.View full abstractDownload PDF (1000K) -
Yoshihiro Takahara, Makoto Oyamada, Takeyuki Hakuraku, Hidehiko Matsud ...1991 Volume 55 Issue 3 Pages 248-253
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIrreversible structural relaxation processes have been investigated for Fe75B10Si15, Fe78B7Si15 and Fe79B10Si11 amorphous alloys by electrical resistivity measurements and Mössbauer spectroscopy.
The electrical resistivity of as-quenched alloys decreased irreversibly with isothermal annealing. Such resistivity changes are mainly associated with decrease of free volume introduced by quenching from the melt. The irreversible decrease of resistivity was reproduced well using the free-volume-Ziman model which was based on the Ziman theory of resistivity and the free-wolume model for viscous flow. The activation energy for annihilation of free volume was evaluated to be 222 kJ/mol (Fe75B10Si15) and 154 kJ/mol (Fe78B7Si15, Fe79B10Si11) from resistivity changes. On the other hand, a significant difference in the annealing behavior of the average isomer shift and internal magnetic field with time between Fe75B10Si15 and Fe78B7Si15 amorphous alloys was observed. This indicates that the local structural change in relaxation process differs much in both amorphous alloys. Such compositional dependence of activation energy and Mössbauer parameters was explained well by the structural model proposed by Dubois et al.View full abstractDownload PDF (854K) -
Osamu Arai, Fujio Abe, Reimon Hanada, Hiroshi Kimura1991 Volume 55 Issue 3 Pages 254-259
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPalladium specimens loaded with hydrogen(H) or deuterium(D) by an electrolytic method were quenched to 4.2 K to study the precipitation process. In the subsequent isochronal annealing experiments, the resistivity increase due to the quenched H was found to decrease between 80 and 150 K. This decrease shows that the H migrates and precipitates at these temperatures. Almost the same results were obtained for D. The onset of the H migration at a relatively high temperature of 80 K as well as the small isotope effect reveal that the mechanism of H diffusion in palladium is nearly classical.
The temperature of the recovery stage was measured as a function of hydrogen concentration and was found to shift to lower temperatures with increasing concentration.
The result was interpreted as the concentration dependence of a nucleation process.
The resistivity increase due to disolved H was measured as a function of the electrolytic charging time and the current density during the specimen preparation. Analysis of the result reveals that about 28% of H ions produced on the specimen surface are absorbed into the bulk. This result might be useful to estimate the time or current density to load H isotopes into Pd to a high concentration as frequently being done in recent fusion research.View full abstractDownload PDF (790K) -
Influence of Oxygen Content on Electrical Resistivity and Phase Constitution in Quenched Ti-V AlloysMasahiko Ikeda, Shin-ya Komatsu, Takashi Sugimoto, Kiyoshi Kamei1991 Volume 55 Issue 3 Pages 260-266
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSpecific resistivity values of Ti-V alloys previously measured by the present authors were slightly different from those reported by Ho and Collings. Such difference may be attributed to different impurity content, especially oxygen, in the samples. The present study was undertaken to elucidate an effect of addition of oxygen on the specific resistivity and the hardness for three series of the alloys, Ti-10 to 40%V, Ti-20%V and Ti-30%V quenched from temperatures of β phase range. Phase constitution at the RT was confirmed by X-ray diffraction.
The following results were obtained:
(1) X-ray phase constitution of Ti-V-0.3%O alloys showed no remarkable difference from previous alloy series containing about 0.1%O. Lower end of V content range showing nagative temperature dependence were lowered by addition of 0.3%O than previous alloy containing 0.1%O. Oxygen addition always increased the ρ values.
(2) Excepting 15%V, oxygen addition increased hardness. In 20%V alloys, hardening was smaller than other alloys, suggesting that an athermal ω volume fraction existing at RT was decreased by the oxygen addition.
(3) In the Ti-20%V-Y%O alloys containing more than 0.2%O, ρLN/ρRT became larger than unity, and temperature of ρ maximum on ρ-T curve was lowered with increasing oxygen content.
(4) The oxygen addition to Ti-30%V alloy showed a less drastic influence on ρ-T curve than the case of Ti-20%V alloy. Temperature coefficient of resistivity decreased with oxygen content, and a minimum of ρ appeared at 240 K by addition of 1.05%O.
(5) These observations indicate that starting and finishing temperatures of the athermal ω formation are lowered with increasing oxygen content.
The difference in measured resistivity values reported by individual investigators may be explained by the difference in oxygen content.View full abstractDownload PDF (1039K) -
Yasuo Fujinaga, Tasaku Sato1991 Volume 55 Issue 3 Pages 267-271
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAn isobaric temperature-composition (T-C) section of the three-dimensional phase diagram of the Ag-Cu system at 7 GPa is constructed on the basis of the results of X-ray diffraction examination, electrical resistance measurement and electron probe microanalyzer (EPMA) analysis.
The phase diagram shows the expansion of the phase fields of the Ag-rich (α) and Cu-rich (β) primary solid solutions with increasing eutectic temperature. The solubility limits of the α and β phases at 7 GPa and 1223 K are determined to be 21 at%Cu in the α and 10 at%Ag in the β phases, respectively.
A three-dimensional T-C-P phase diagram is also proposed on the basis of the T-C phase diagrams at ambient pressure and 7 GPa as well as melting curves of silver, copper and the eutectic alloy.View full abstractDownload PDF (703K) -
Kazuyuki Ogawa, Shozo Ikeda, Kimiko Sakata1991 Volume 55 Issue 3 Pages 272-278
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSLattice images of Y2O3 are observed by a high resolution electron microscope. Because Y2O3 belongs to the body-centered C-Rare earth Ia\bar3 structure, oxygen vacancies along ⟨111⟩ direction induce a shift of atoms from the CaF2 structure. The periodicity of the obtained lattice images corresponds with that of the projected pattern, where the periodicity is influenced by the shifts Y atoms. For the (001) projection, the images of two neighboring lattice planes make a pair to ⟨100⟩ directions and the 110 spots of the optical diffraction pattern are missing as expected by the projected pattern of the Ia\bar3 structure. For the (111) planes, images of Y atoms make zigzag lines for the shift. For the (110) and (111) planes, the same type of lattice image appears every four layers to the ⟨110⟩ directions. Because the forbidden 110 reflection spots appeared and the fourfold period of lattice image was not clear for very thin area, the structure images of the (110) and (111) planes may include contribution of the double reflection of electron beam.View full abstractDownload PDF (2074K) -
A. Toshimitsu , Jr. Yokobori, Takeshi Isogai1991 Volume 55 Issue 3 Pages 279-285
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe dislocation groups dynamics emitted from the stressed source was analysed under the stress singularity at the crack tip. From this analysis, the mechanical significance of dislocation free zone was clarified. That is, the length of dislocation free zone (DFZ) is a function of applied stress rate, and inverse pile up against the back tip of the dislocation free zone occurs. The maximum dislocation density at the tip of DFZ was represented by the double logarithmic linear function of the length of DFZ. From this analysis, it was shown that fracture occurs within DFZ and dynamic fracture strength decreases with increasing applied stress rate. Furthermore, the scattering of the trigger point for brittle fracture in the region of brittle-ductile transition was clarified by this model and the proposed model of dislocation pile-up. These analysis enable to discriminate brittleness of materials.View full abstractDownload PDF (772K) -
Eiji Inoue, Taku Sakai1991 Volume 55 Issue 3 Pages 286-293
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSHot deformation of a 3%Si steel was studied in compression at the temperatures ranging from 1073 to 1273 K and at constant true strain rates of 10−5 s−1 to 10−1 s−1 by using a microcomputer-aided new testing system. The temperature-corrected strain rate Z vs. yield stress relationship can be approximated by a power law. By contrast, Z vs. steady state flow stress can be approximated by two power law relationships, which are valid above or below Zc\simeq1011 s−1, respectively. The grain morphology compressed to high strains is pan-caked type at Z>Zc, but approaches equiaxed type with decreasing Z below Zc. These suggest that deformation at Z<Zc can be controlled by slip in grain interior and additionally by grain boundary zone shear, the latter leading to the lower work hardening and the development of equiaxed grains.
The flow behavior at constant true strain rates is clearly different from that at constant crosshead speeds. This results from the differences not only in true strain rates, but also in deformation hysteresis. It is concluded that an unsteady or transient state flow takes place at high strains during deformation at constant speeds, while a steady state flow occurs at constant true strain rates.View full abstractDownload PDF (2008K) -
Toshio Shimoo, Masaki Sugimoto, Yoshiharu Kakehi, Kiyohito Okamura1991 Volume 55 Issue 3 Pages 294-303
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTo investigate the mechanism of the pyrolysis of Si-Ti-C-O fibre (Tyranno), the rate of pyrolysis has been measured with a thermobalance at temperatures from 1673 to 1973 K under an argon atmosphere. The pyrolysis product was examined by chemical analysis, X-ray diffraction and TEM observation. Results were compared with those of Ti free fibre (Nicalon).
The amorphous Si-Ti-C-O fibre crystallized to β-SiC and TiC, with evolution of SiO and CO. TEM observation showed the spherical growth of the crystallites of SiC. The pyrolytic rate of Si-Ti-C-O fibre was larger than that of Si-C-O fibre (Nicalon). While the crystallites of SiC in Nicalon grew markedly during holding at high temperatures after the completion of the pyrolysis, the coarsening of the crystallites in Tyranno was retard.
The pyrolytic rate was analyzed by means of Avrami-Erofeev equation. The mean value of the exponent in the rate equation was m=1.4. The activation energy was 368 kJ/mol. The pyrolysis of Si-Ti-C-O fibre was controlled by the nucleation and growth of SiC crystallites.View full abstractDownload PDF (2608K) -
Ryo Inoue, Takuma Kozono, Ryozo Goto, Hideaki Suito1991 Volume 55 Issue 3 Pages 304-309
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEffects of HCl, Fe, Na and K in the determination of nitrogen as NH4+ have been studied by the method of Ion-chromatography. The analyzed value of nitrogen was reduced in the presence of HCl (>9×10−5 mol) and K (≥2 μg) in the injected solution, while that was scarcely influenced by 120 μg of Fe or 30 μg of Na. In the analysis of ultra low content of nitrogen in steel or slag, 1 mass ppm of nitrogen in the sample was determined with CV-value=3.5% by a combination of the steam-distillation method and ion-chromatography.View full abstractDownload PDF (640K) -
Masakazu Niinae, Isamu Saito, Hiroshi Sakamoto, Yoshitaka Nakahiro, Ta ...1991 Volume 55 Issue 3 Pages 310-315
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of diluents on extraction of cobalt from weakly acidic solutions with di-(2-ethylhexyl) phosphoric acid (D2EHPA) in various low polar diluents such as n-heptane, cyclohexane, m-xylene, toluene, o-xylene, benzene and n-heptane-benzene mixtures was studied on the basis of the regular solution theory.
As the result of the study, it was found that the dependence of the apparent thermodynamic extraction constants (logK°d,1, with an infinite dilution as the reference state, or the extraction constants (logKd,1)) and the distribution coefficients (logD) on the solubility parameters (δd) of individual diluents could be expressed by second order equations.
In the case of mixed diluents of n-heptane-benzene, it was also found that the dependence of the apparent thermodynamic extraction constants (logK°d,2, with an infinite dilution as the reference state, or the extraction constants (logKd,2)) and the distribution coefficients on the diluent composition could be semi-empirically expressed by first order equations.View full abstractDownload PDF (780K) -
Setsuo Aso, Keisaku Ogi1991 Volume 55 Issue 3 Pages 316-323
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTo clarify eutectic solidification processes of Fe-5%Cr/15%Cr-C-B alloys, eutectic irons containing 5 or 15%Cr, 0.06 to 3.2%C and 0.5 to 3%B were remelted in a Bridgman type furnace at 1723 K and then quenched by water jet spray while freezing unidirectionally at 2.8×10−6 m/s. The species and structures of eutectic phases were examined by using X-ray diffraction and metallographic techniques. Redistribution of solute elements during eutectic growth was analyzed by EPMA. The eutectic compositions of 5 and 15%Cr alloys varied continuously from 4.2%C-0%B and 3.7%C-0%B to 0%C-3.6%B and 0%C-2.5%B (in 5%Cr alloys and 15%Cr alloys), respectively. The γ-Fe3 (C, B) or γ-Fe2B eutectic appeared in 5%Cr alloys depending on B content. In 15%Cr alloys, the γ-Cr7 (C, B)3, γ-Fe23 (C, B)6 or γ-Cr2B eutectic crystallized first, followed by the γ-Fe3 (C, B) eutectic. The γ-Fe3 (C, B) eutectic of the lower B alloy grew in a so-called ledeburite structure, while that of the higher B alloy froze in lamellar structure. The other eutectic grew in anomalous structure. The chromium content of intercellular liquid decreased in all the cases, as the distance from cell tip increased. The B content increased and the C content decreased in the lower B alloys, while they were distributed inversely in the higher B alloys. Because of these changes in liquid composition, the secondary eutectic γ-Fe3 (C, B) crystallized in 15%Cr alloys.View full abstractDownload PDF (2366K) -
Seigi Aoyama, Mituaki Onuki, Yasuhiko Miyake, Ryoichi Urao1991 Volume 55 Issue 3 Pages 324-329
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effects of pre-heating at 873 K on softening during annealing of cold-drawn copper wires containing lead were studied in relation to lead concentration. Annealing behavior of cold-drawn copper wires containing lead and antimony or lead and nickel were also studied. Hot-rolled copper wires after pre-heating were cold-drawn to 90% reduction and annealed at 293-673 K for 3.6 ks. The annealed copper wires were subjected to tensile tests and observations of the microstructure.
The half-softening temperature of cold-drawn copper wires without the pre-heating increases with lead concentration from 1 to 590 mass ppm and the half-softening temperature of the pre-heated and cold-drawn copper wire is lower than that of the cold-drawn wire without the pre-heating. The enhancement of softening is due to recrystallization enhancement by the decrease of lead dissolved in the copper matrix and the formation of Pb-oxide.
When lead and antimony coexist in copper, the enhancement of softening is suppressed. When lead and nickel coexist in copper, the softening rate is not affected.
The effects of lead on the enhancement of softening and the effects of antimony and nickel on the enhancement of softening during annealing of cold-drawn copper wire containing lead are clarified.View full abstractDownload PDF (956K) -
Kunimasa Takeshita, Hisashi Takada1991 Volume 55 Issue 3 Pages 330-336
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn this investigation, Ag-Al-Sn filler alloys are identified to allow the brazing of titanium at a temperature well below its α-β transformation temperature of 1155 K and to afford good strength of the brazed joint.
Sn addition to Ag-Al filler alloys has a significant effect on the drop of their liquidus temperatures and the improvement in wetting to the base metal of titanium.
The tensile strength of butt-joint specimens brazed with Ag-5, 10, 15 mass%Al filler alloys containing 2.5 or 5 mass%Sn are, however, 100 to 170 MPa lower than or equal to those brazed with Ag-5, 10, 15 mass%Al filler alloys.
In the case of the Ag-20 mass%Al filler alloy, Sn addition by 2.5 mass% to this filler alloy improves the tensile strength of the brazed butt-joint specimen, the value of which is 290 MPa. Furtheremore, the Ag-20 mass%Al-2.5 mass%Sn filler alloy enables titanium to be brazed at 1000 K, which is 155 K lower than the α-β transformation temperature of titanium.View full abstractDownload PDF (1545K) -
Ryuuji Watanabe, Hisashi Andoh, Kiyoji Iwashita, Yukio Kurosawa1991 Volume 55 Issue 3 Pages 337-343
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSeveral electrodes were fabricated using Ni3Al-Cr and NiAl-Cr alloys for high withstand-voltage vacuum circuit breakers. The microstructure and basic electrical properties for the electrodes were studied. Cr particles were detected and found to be dispersed homogeneously in these alloys.
Ni3Al-Cr and NiAl-Cr electrodes have a high withstand-voltage with a mean value of 110 kV.
Further more, the electrodes were found to be comparable in performance to conventional of copper alloys electrodes in their interruption-ability and chopping-current. These Ni-Al-Cr alloys show promise as a practical electrode material for high voltage vacuum circuit breakers.View full abstractDownload PDF (2345K) -
Tsuneo Kuroda, Hitoshi Wada1991 Volume 55 Issue 3 Pages 344-350
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBecause of large upper critical fields above 30 T at 4.2 K, the Nb3Al superconductor may be regarded as promising for high field superconducting magnet use. Nb3Al multifilamentary wires which have recently been fabricated by a modified composite diffusion process show the high critical current densities at high fields, comparable to those for practical Nb3Sn wires. In this study effects of tensile strain on superconducting properties in the Nb3Al multifilamentary wires have been investigated to see if these wires are useful for applications where superconductors are subjected to high mechanical loads.
Critical temperatures and currents have been studied for multifilamentary wires containing more than 1 million of Nb3Al filaments as a function of applied tensile strain. Relations of critical currents under strain to composite configurations and microstructures of wires are examined through tensile tests and scanning electron microscopic observations of fractured surfaces.
While critical currents for samples with Al-Mg or Al-Cu-Ge alloy cores in the Nb matrix decrease monotonically with applied strain, samples with a Cu-Ni alloy sheath around the Nb matrix show peaks in the critical currents vs. strain curves. The strains for the occurrence of permanent degradation in critical current have been more than 1% and the strain dependences of critical currents in these Nb3Al wires have been much smaller than that for Nb3Sn wires.View full abstractDownload PDF (1464K) -
Yasushi Ikai, Takashi Takemura, Hisaki Miyamoto1991 Volume 55 Issue 3 Pages 351-352
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (230K)
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