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Volume 58, Issue 3
Displaying 1-18 of 18 articles from this issue
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Yoshihiro Takahara, Junichi Tamenari, Hidehiko Matsuda1994 Volume 58 Issue 3 Pages 245-251
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe compositional dependence of the crystallization process at constant rate heating has been studied for Fe-B-Si amorphous alloys by electrical resistance measurement and differential scanning calorimetry (DSC). The crystallization products have been examined by X-ray diffraction. The relationship between the crystallization process and the amorphous structure was discussed in terms of the Dubois and Le Caer’s structural model.
A strong compositional dependence was observed in the changes in electrical resistivity and DSC curve during the crystallization. Based on the way of the changes in the physical properties, the crystallization process was classified into five groups. Furthermore, it was found that the crystallization process changed significantly at a critical concentration where the structural change was predicted from the model. Outside the critical concentration amorphous alloys crystallized at temperatures above 800 K and produced Fe3B and Fe2B as well as Fe3Si at the initial stage. Inside the concentration α-Fe(Si) or Fe3Si appeared as the primary crystalline phase and then Fe-B compounds emerged from the remaining amorphous phase. The formation of the metastable Fe3B phase is considered to be closely related to the order-disorder transformation in the Fe-Si phase which appears in the initial stage of crystallization.View full abstractDownload PDF (599K) -
Kenji Matsuda, Shizuo Tada, Susumu Ikeno1994 Volume 58 Issue 3 Pages 252-259
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe morphology of planer precipitates and the orientation relationships between the precipitates and the matrix in an Al-1.0 mass%Mg2Si-0.4 mass%Si alloy were investigated by transmission electron microscopy (TEM).
Some equilateral triangular precipitates and many polygonal precipitates were observed by a scanning electron microscope. TEM observation of the precipitates and the extracted precipitates from the matrix by thermal phenol method shows that the equilateral triangular precipitates are thin plates. The electron diffraction patterns taken from these precipitates were analyzed as a silicon that has a diamond structure (a=0.543 nm). Energy dispersive X-ray spectroscopic (EDS) analysis measured at the extracted precipitates showed only Si peak. Some straight boundaries exist in the equilateral triangular precipitate. It was observed by high resolution electron microscopy that the boundaries are plane defects such as stacking faults. Electron diffraction spots taken from this precipitate show the forbbiden reflection. Such spots are caused by stacking faults.
Therefore, the equilateral triangular precipitate is silicon. Orientation relationships between the precipitate and the matrix is as follows; (001)Al\varparallel(111)Si and the angle between [100]Al and [\bar110]Si is 10 degrees. Three sides of the triangular Si precipitate are parallel to the direction of ⟨110⟩Si in (111)Si.View full abstractDownload PDF (2207K) -
Yasuhiro Uetani, Hideki Murase, Kenji Matsuda, Hiroshi Anada, Shizuo T ...1994 Volume 58 Issue 3 Pages 260-266
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSLocalized deformation near grain boundaries in an Al-0.996 mass%Mg2Si-0.395 mass%Si alloy was investigated by interference microscopy and scanning tunneling microscopy.
Both the displacement of scratch lines and the steps at the grain boundaries were observed. The number of the grain boundaries with displacement of scratch lines had a maximum at the grain boundaries making angles of about 45 degrees to the tensile axis. While a large numbers of the steps were observed at the grain boundaries making angles of near 90 degrees to the tensile axis. In both types of grain boundaries, the direction of the maximum resolved shear stress (corresponding to Fmax) on a grain boundary plane is close to the moving direction of the grain boundary.
When the step was formed simultaneously at two neighboring grain boundaries, fold was not observed. In such a case, the direction of Fmax on the grain boundary plane was slightly deviated from the moving direction. The values of Fobs (corresponding to the resolved shear stress on the grain boundary plane in the moving direction) tended to increase with the amounts of steps and displacements of scratch lines at the grain boundaries.View full abstractDownload PDF (832K) -
Hiromi Miura, Hiroshi Aoyama, Taku Sakai1994 Volume 58 Issue 3 Pages 267-275
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of grain-boundary character on dynamic recrystallization was studied by means of hot-tensile tests and metallographic observations. For this purpose, Cu-Si alloy bicrystals having several [001] twist boundaries were hot-deformed at a temperature of 1023 K and a strain rate of 4.17×10−4s−1, followed by H2 gas quenching. As misorientation angle (grain-boundary energy) increases, dynamic recrystallization took place easier at grain boundary. This grain-boundary dependent characteristic of dynamic recrystallization was closely attributable to the difference in the occurrence of grain-boundary sliding, grain-boundary serration and piling up of dislocations to grain boundary followed by the development of inhomogeneous dislocation substructure nearby grain boundary. Accompanying these results, a new model of dynamic recrystallization, in which dynamic nuclei can be formed by bulging out of part serrated grain-boundary, is proposed.View full abstractDownload PDF (2938K) -
Masao Morishita, Koichiro Koyama, Kazuhiro Yamazoe, Masahiko Morinaga, ...1994 Volume 58 Issue 3 Pages 276-282
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSElectronic states of the molten chlorides of alkali metals, magnesium and zinc have been investigated using DV-Xα molecular orbital calculation. Bond order and ionisity were utilized to clarify charge distributions between metal ions and chlorine ions. The results are as follows:
(1) Within the molten chlorides of alkali metals, as the atomic number increases, the ionisity becomes higher and the bond order becomes lower, that is, the strength of the covalent bond becomes lower.
(2) The molten chlorides of magnesium and zinc metals are higher in the strength of covalent bond than the molten chlorides of alkali metals. This is probably the reason for the formation of the complex ions of the molten chlorides of magnesium and zinc.
(3) It was found that the molten chlorides with higher bond order values showed the lower equivalent conductivities.
Thus, it is found that the molecular orbital calculation is very useful in investigating the electronic states of molten salts.View full abstractDownload PDF (614K) -
Masao Fujishige, Koichi Tabei, Hajime Ino, Toshihide Takenaka, Masahir ...1994 Volume 58 Issue 3 Pages 283-290
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe hydrogenation of calcium carbide to CaH2 in H2 gas flow has been investigated with a pressurized container. The hydrogenation rate was estimated by the analysis of exhausted gas and the chemical analysis of products.
Calcium carbide was converted to CaH2 perfectly even at a relatively low H2 pressure (1.1 MPa) though the reaction rate was not efficiently high. The reaction rate depended upon the surface area of a sample, H2 pressure and temperature. Calcium hydroxide on the surface of the sample, which was formed by the reaction with CaC2 and H2O in air, caused the carbon deposition during heating, but it was removed at the early stage of hydrogenation under a pressurized condition.View full abstractDownload PDF (1028K) -
Katsutoshi Matsumoto, Shoji Taniguchi, Atsushi Kikuchi1994 Volume 58 Issue 3 Pages 291-296
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA kinetic study on the leaching of Fe2O3 in HNO3 solutions has been made by using agitated vessel. Three types of powder specimens, (A) reagent grade Fe2O3, (B) calcinated FeC2O4 and (C) sintered Fe2O3, were sized by a wet classification. The specific areas of these specimens were measured before and after the leaching experiments. Leaching rates of the powder specimens were measured at various conditions of rotation speed of the stirrer (n), concentration of HNO3(CHNO3), and liquid temperature (T). A microscopic observation of a polished surface of a sintered Fe2O3 disk was also made after exposing the surface in HNO3 solution.
The initial leaching rate was found to be independent of n and proportional to CHNO3 and initial specific area. The apparent activation energy was 82 kJ/mol. The leaching rate beyond initial stage increased with increasing time, in spite of very small change in the specific area with leaching. From the micrograph of a partly dissolved surface of a sintered Fe2O3 disk, only the (0001) oriented crystal planes were dissolved and its surface showed coarse irregularities. From these results, the acceleration of the leaching rate was thought to be caused by the anisotropic dissolution and the increase in the surface area of the (0001) plane at the surface of each Fe2O3 particle.View full abstractDownload PDF (931K) -
Katsutoshi Matsumoto, Shoji Taniguchi, Atsushi Kikuchi1994 Volume 58 Issue 3 Pages 297-302
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA kinetic study on the leaching of Fe2O3 in HCl solutions has been made by using agitated vessel to clarify the machanism of the rate acceleration which was found in the previous study for Fe2O3-HNO3 system. Powder specimens with various sizes were prepared by a wet classification of ground powder obtained from pellets sintered at 1623 K (I) and 1523 K (II). The specific areas of these specimens were measured before and after the leaching experiments. Leaching rates were found to be independent of the agitation speed. Leaching rates under various conditions were correlated by the following relationship:
(This article is not displayable. Please see full text pdf.)
\ oindentwhere α is the fraction dissolved, Sw0 the initial specific area of the specimen, T temperature, C concentration of ionic species. As seen in the above correlation, the leaching rate increased with increasing α. In order to clarify the mechanism of the rate acceleration, a leaching experiment was carried out by using a sintered Fe2O3 disk of which surface was polished and exposed to a HCl solution. Same as the previous study, only the (0001) oriented crystal planes were found to dissolve and its dissolution rate increased with time. The fractional area of the (0001) plane was about 25%. Assuming the same fractional area for the powder specimen, the increase in the overall surface area was well estimated.View full abstractDownload PDF (655K) -
Hidehiko Kamide, Yuichi Tanaka1994 Volume 58 Issue 3 Pages 303-308
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe tensile test of 304 stainless steel on which copper and constantan wires were welded to constitute a thermocouple was done to clear the effect of heat generation due to plastic deformation on current density in H2SO4-NaCl solution at −300 mV (vs SCE).
The temperature and current density of specimens during plastic deformation increased with increasing strain and strain rate. A linear relationship was obtained between logarithm of increased current density with deformation in each strain and real specimen temperature which rised temperature with deformation was added to solution temperature. From this relation, the ratio R of current density due to rised temperature with deformation to current density at real specimen temperature during plastic deformation increased with increasing strain and strain rate \dotε. Relationships between R and \dotε in each strain were obtained for the strain rate range from 5.6×10−3s−1 to 1.1×10−1s−1 as the following equations.
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\ oindentThis rised temperature during plastic deformation did not detect under the strain rate of 5.6×10−5s−1. But it was thought that strain rate at crack tips remarkably increased after crack initiation. Therefore, it is suggested that heat generation due to plastic deformation does not affect to the process of crack initiation but is able to affect to the process of crack propagation in stress corrosion cracking.View full abstractDownload PDF (465K) -
Noboru Akao, Takayuki Matsuda, Katsuhisa Sugimoto1994 Volume 58 Issue 3 Pages 309-317
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of Dy content on the corrosion resistance of sputter-deposited TbDyFeCo alloy films for magneto-optical recording media was investigated by means of immersion corrosion tests and electrochemical polarization measurements. Surface films on the alloy were analyzed by X-ray photoelectron spectroscopy(XPS) after the immersion corrosion tests. As reference specimens, TbDyFeCo alloy tapes prepared by a melt span method were also used.
The corrosion mass loss of the alloy films in 0.01 kmol·m−3 NaCl increased with increasing Dy content of the films. The same results were obtained on the alloy tapes. The selective dissolution of Fe and Co to test solutions and the concentration of Tb and Dy in surface films were found after the immersion corrosion tests. Surface films on TbDyFeCo alloys were composed of hydroxides and oxides of Tb, Dy and Fe. The quantities of hydroxide and oxide of Dy increased after the immersion corrosion tests. Anodic current densities in both the active and passive states increased and the pitting potential decreased with increasing Dy content of the alloys. This shows the stability of passive films is deteriorated by the Dy addition to the alloy.View full abstractDownload PDF (869K) -
Hidetoshi Saitoh, Bun Tsuchiya, Tatsuya Mochida, Ryoichi Urao1994 Volume 58 Issue 3 Pages 318-323
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA Monte Carlo computer simulation was performed to investigate the fundamental roles of N2+ acceleration in an ion nitriding process. The calculation results showed incident energy of N2+ to the cathode was mainly affected by the changing gas temperature when the electric field was assumed to be unchanged. Therefore incident energy increases with increasing gas temperature in a cathode fall region. In addition, two major roles of N2+ acceleration were proposed; (1) direct gas heating in the region near the cathode and (2) sputtering for the surface of the cathode. In order to reveal the effects of the increasing gas temperature or sputtering rate on well-nitriding, the samples of SCM420 were treated using dc plasma reactor with a tungsten hot filament. In this equipment, the reactant gas is heated directly by the hot filament settled around the cathode. Therefore incident energy of cations can be controlled with changing filament temperature. The nitriding speed of the sample increased with increasing filament temperatures in the range of ≤1610 K, suggesting that the amount of radicals required for nitriding becomes larger with increasing gas temperature. However nitriding was inhibited over 1610 K because of the increase in sputtering rate by cations incident on the sample. These results suggest that the optimum acceleration of N2+ affects for well-nitriding through gas and sample heating. However, exceeded acceleration gives the sample severe sputtering, resulting in the inhibition of well-nitriding.View full abstractDownload PDF (573K) -
Tatsuya Ohmi, Kouki Minoguch, Masayuki Kudoh, Youichi Itoh, Kiyotaka M ...1994 Volume 58 Issue 3 Pages 324-329
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe principle of a new process to produce the semi-solid slurry of hypereutectic Al-Si alloy containing fine primary silicon crystals has been proposed: the process was named “slurry-melt mixing (SMM)” process. In this process, a phosphorus-added hypereutectic Al-Si alloy melt (second-alloy melt) was mixed with a semi-solid slurry of a hypoeutectic Al-Si alloy (first-alloy slurry) under a furnace-cooling atmosphere. As the two kinds of alloys were brought into contact with each other with agitation, the second-alloy melt was rapidly quenched to precipitate numerous fine primary silicon crystals, while the equiaxed alpha solid solution in the first-alloy slurry was remelted absorbing the latent heat of fusion. And the enthalpy balance of the two alloys led the mixed alloy to a stable solid-liquid coexisting state.
Al-20 mass%Si alloy slurry was produced by the SMM process with the combination of an Al-8 mass%Si alloy and a phosphorus-added Al-32 mass%Si alloy. The arithmetic mean of area-equivalent diameters of the primary silicon crystals in the SMM slurry was 27 μm. The fluidity of the SMM slurry could be kept for about 1000 s because of the low cooling rate of the atmosphere. Sodium-addition into the SMM slurry makes it possible to achieve the modification of the eutectic silicon crystals without the coarsening of the primary silicon crystals.View full abstractDownload PDF (1020K) -
Shigeta Hara, Masanobu Watanabe, Kiyoshi Nogi, Kazumi Ogino1994 Volume 58 Issue 3 Pages 330-336
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSWetting of a solid graphite by carbon saturated Fe-Ni liquid alloys was studied by the sessile drop method at 1623 K. The results are summarized as follows, (1) Surface tension of the liquid alloys was 1720±40 mN/m which showed no composition dependence. (2) It was found that the advancing contact angle, which was measured by increasing the metal-graphite interface, is higher than that of the receding state, namely the hysteresis of wetting. (3) The advancing contact angle is the same as that observed when the liquid alloy at carbon saturation was dropped on the graphite substrate, while the receding one is close to the value obtained when the carbon-free liquid was melted on the graphite substrate. (4) The difference between the advancing and receding contact angles was discussed by Aksay’s model.View full abstractDownload PDF (879K) -
Hiroyuki Toda, Toshiro Kobayashi1994 Volume 58 Issue 3 Pages 337-345
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSShort crack propagation behaviour of 6061 aluminum alloy with and without SiC whisker was investigated.
Short fatigue cracks initiate and grow in a much lower ΔK range than the threshold stress intensity ranges, ΔKth, of long fatigue cracks in both materials. In addition, there exists a growth dip in the MMC, and it could be explained by measured abrupt awakening of crack closure which is mainly induced by asperity contact.
Statistic scatter in the growth rates of microstructurally short crack is observed in both of the materials. The distribution of crack growth rates well follows a three parameter Weibull distribution function. The shape parameters of this distribution function which reflects the extent of scatter in the crack growth rates are initially small in both of the materials and they increase and close to the respective asymtotic lines with increasing crack length. The crack length range when the scatter converges is 110∼183 μm for the unreinforced alloy and 25∼40 μm for the composite. This is considered as upper bounds of microstructurally short cracks. The differences in crack length may be attributed to the respective crack growth mechanisms that crystallographic crack growths such as slip band cracking and intergranular cracking, which are generally observed in the unreinforced alloy, are suppressed in the MMC due to the existence of closely spaced reinforcement, and a microstructurally short crack mainly interacts with reinforcement itself and a packet of whiskers.View full abstractDownload PDF (1467K) -
Seishi Abe, Yoshitaka Furukawa, Katsumi Mochizuki, Katashi Masumoto1994 Volume 58 Issue 3 Pages 346-352
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSLead chalcogenide solid solution semiconductors are expected to be applied to tunable laser diodes, which operate in the mid-infrared wavelength region between 3 and 4×10−6 m ranges. The laser diode is considered to be mainly utilized to an advanced measurement system for detecting hydrocarbon pollutants in air and also to a new optical fiber communication system over super long distances, which has not been developed yet. In order to put this laser diode to practical use, it is required to operate at room temperature. In this study, we proposed a new quaternary solid solution semiconductor Pb1−xCaxS1−ySey for the cladding layer in a double-hetero or quantumn well structure laser. In our preceding study, it was revealed that the Pb1−xCaxS1−ySey semiconductor was one of the excellent materials for mid-infrared laser diodes compared with the conventional ones. Based on the result, we tryed to fabricate Pb1−xCaxS1−ySey (y=0) thin films by the hot wall epitaxy method and examined their semiconducting properties.
It is expected that this laser diode with double-hetero structure has a higher operating temperature than that of the ones reported previously.View full abstractDownload PDF (622K) -
Tetsuya Watanabe, Masayuki Hasaka, Takanori Miyase1994 Volume 58 Issue 3 Pages 353-358
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe objective of this paper is to fabricate a thermoelectric semiconductor with high-generating power. After powders were prepared from the melt-spun ribbons of FeSi2-1 at%M (M=B, Mn, Co) which were made by a single roll method, they were sintered with Ag-powder or AgNO3-solution. When the powders of FeSi2-1 at%Co were sintered with AgNO3-solution, the large power factor is obtained due to the reduced electrical resistivity.View full abstractDownload PDF (526K) -
Fumiyoshi Kirino, Norio Ohta, Fumio Kugiya1994 Volume 58 Issue 3 Pages 359-367
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe relationship between the thermal stability and the magnetic characteristics of an amorphous magneto-optical recording film was studied by using TbFeCoNb and TbFeCoNbPt films with same curie temperature and the compensation temperature. The film with small decrease of the perpendiculer anisotropy of addition of elements such as Nb, or Pt and Nb, had a high thermal stability. However, the perpendicular anisotropy of the film with the addition of Pt and Nb decreased more than 1/10. When the film was annealed at 250°C, the perpendiculer anisotropy was disappeared. From the results of Auger electron spectroscopy, the differential thermal analysis, the X-ray diffraction method and the magnetic torque measurement, this change of the perpendicular anisotropy is not caused by the crystallization of the recording film or the oxidation of the film, but by the structure relaxation. As a result, it is found that the important factor for the thermal stability of the film is to control the change of the perpendicular anisotropy with less than the desired constant value.View full abstractDownload PDF (1200K) -
Fumiyoshi Kirino, Shigenori Okamine, Norio Ohta1994 Volume 58 Issue 3 Pages 368-375
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCu-X alloy film (X=Al, Ni, Mn) such as the reflective film of the quadri-layer structure magneto-optical disk was studied. Cupper has the high reflective index of 97%, but has too high thermal conductivity for magneto-optical recording. For the control of the thermal conductivity and increasing the corrosion resistance, Al, Ni, and Mn was added to Cu. The thermal conductivity were measured by the resistivity of the metal alloy films. The magneto-optical disk (glass substrate/SiNX(85 nm)/TbFeCo(30 nm)/SiNX(20 nm)/CuAl layer(50 nm)) was produced, using the Cu88Al12 alloy film, which has the highest reflective index of 94.5% (λ=830 nm) in these Cu-X alloys (X=Al, Ni, Mn). The C/N (carrier to noise ratio) of this disk increases to 1 dB more than the disk using the Al reflective layer (carrier level is 1 dB larger than the disk using the Al reflective layer and the noise level is increasing 2 dB). That the noise level is higher than the disk using the CuAl reflective film is caused by surface state or the cristarization of the Al film. The recording film whose thickness is thinner than 30 nm, is effective for increasing the carrier level, whose thickness is calculated by the computer simulation. The characteristics of the write/erase repetition were measured. The repetition cycle is more than 107 cycles. The corrosion resistance of Cu-X films (X=Al, Ni, and Mn) was studied. The Cu-X film is weak to the wet corrosion (using the acceleration atmosphere such as 80°C and relative humidity: 95%) and the pitting corrosion (using the acceleration atmosphere such as 1 N NaClaq).View full abstractDownload PDF (1201K)
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