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Volume 50, Issue 2
Displaying 1-18 of 18 articles from this issue
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Hiromichi Horie, Kumi Ochiai, Itsuo Arima, Mikio Morita1986 Volume 50 Issue 2 Pages 127-132
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSHigh frequency magnetic properties of composites for magnetic core, made from magnetic metal powder and resin compound, were investigated.
The effects of specific resistance and mean particle size of magnetic powders on the high frequency magnetic properties were examined. Magnetic metal powder was surface treated by using a coupling agent to obtain good insulation between metal particles.
The following results were obtained. Composites for magnetic core have a high effective permeability at high frequency up to 500 kHz and also have a large saturation induction over 1T.View full abstractDownload PDF (1285K) -
Tsuneo Takahashi, Tatsuo Sato1986 Volume 50 Issue 2 Pages 133-140
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe formation of a modulated structure and an ordered structure in concentrated Al-Mg alloys during the low temperature aging was investigated by means of hardness measurements, specific heat measurements at low temperatures and transmission electron microscopy.
Two types of heat absorption due to dissolution of both the modulated and L12 ordered structures were observed distinctly in the specific heat curves below a certain critical temperture. Through the precise analysis of heat evolution and absorption, the dependence of these structural changes upon the aging temperature and time was clarified. Both the modulated and L12 ordered structures are formed below 353 K, only the L12 ordered structure is formed at 358 K and none of them are formed above 363 K in an Al-14%Mg alloy. Consequently, the L12 ordered structure is found to be formed in two modes; i.e. one is a continuous formation from the modulated structue and the other the nucleation and growth in the matrix.View full abstractDownload PDF (1613K) -
Susumu Onaka, Masaharu Kato, Ryohei Tanaka1986 Volume 50 Issue 2 Pages 141-147
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to clarify the mechanism of the so-called intermediate temperature embrittlement, Cu-GeO2 dispersion-hardened alloys were tensile tested at various temperatures between room temperature and 900 K with the strain rate of either 10−3 s−1 or 10−4 s−1. In the case of single crystals, elongation till fracture increased monotonically with increase in temperature. On the other hand, the ductility of polycrystals first decreased, and then increased again, showing the ductility minimum associated with intergranular fracture at an intermediate temperature range around 600 K. The degree of such intermediate temperature embrittlement was sensitive to both the strain rate and the size of GeO2 particles at grain-boundaries. Microscopic observation of deformation and fracture characteristics of polycrystalline samples indicated that the initial decrease of ductility occurred concurrently with the occurrence of grain-boundary sliding and that the recovery of ductility at higher temperatures was due to the initiation of extensive recrystallization. From these experimental results, it is concluded that at the intermediate temperature range, local stress which concentrates near the GeO2 particles at the sliding grain-boundary induces the formation of voids which eventually grow and coalesce to cause intergranular fracture. At higher temperatures, the stress concentration is relaxed by the recrystallization, resulting in the recovery of ductility. The effects of strain rate and particle size on the intermediate temperature embrittlement were also discussed in association with the occurrence and disappearance of the stress concentration.View full abstractDownload PDF (2484K) -
Hisashi Itoh, Mitsuo Kido, Keijiro Nakasa, Hideo Takei1986 Volume 50 Issue 2 Pages 148-153
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe crack propagation velocity in delayed failure was measured under repeated and static load, using specimens with various pre-austenite grain size of JIS SNCM 439 steel quenched and tempered at 473 K. Main results obtained are as follows:
(1) The crack propagation velocity in delayed failure under static load, da⁄dt, is varied with the pre-austenite grain size, d, and da⁄dt is the largest in the specimen of d=15 μm, followed by those of d=5 μm and 30 μm.
(2) There appear two peaks on the relationship between the frequency, f, and the decrease rate of crack propagation velociy, 1−β=((da⁄dt)S−(da⁄dt)R)⁄(da⁄dt)S, where (da⁄dt)S and (da⁄dt)R are the crack propagation velocity under static and repeated stress, respectively. The frequencies at which these peaks appear are the highest in the specimen with grain size of d=15 μm, followed by those with 5 μm and 30 μm. The height of these peaks is decreased with increase in the grain size d.View full abstractDownload PDF (879K) -
Shoji Goto, Kazuhiko Mori, Hideo Yoshinaga1986 Volume 50 Issue 2 Pages 154-161
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to investigate the shape effect of the particles on the high-temperature strength of dispersion-hardened alloys, two kinds of nickel alloys with SiO2 particles of complex and spherical shapes were made by internal oxidation only and a heat-treatment after the internal oxidation, respectively. Their strengths were measured by means of tensile test at high temperatures.
The modulus-corrected yield stress increment of the alloy with particles of complex shape depended neither on the temperature nore on the strain rate, and agreed with the Orowan stress calculated from the observed dispersion, which suggested that the effect of dislocation climb over the particles was effectively suppressed by making the particle shape complex. While, the yield stress increment of the alloy with particles of spherical shape agreed with the value of Orowan stress at room temperature but decreased with increasing temperature and decreasing strain rate at 1173 K, which suggested that the effect of dislocation climb was large for the spherical particles.
Because of the higher planar number-density of particles, the Orowan stress of the alloy with complex shaped particles was always higher than that with spherical ones.
From the result mentioned above, the complex shaped particle was found to be effective for dispersion hardening at high temperatures.View full abstractDownload PDF (1887K) -
Shoji Goto, Yuzo Nishijima, Hideo Yoshinaga1986 Volume 50 Issue 2 Pages 162-167
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThermal stability of the lamellar structure in a Mo-TiC eutectic composite has been investigated through the heat-treatment at 1523-2223 K for 5.76×104−3.6×105 s under a low vacuum pressure of 13 mPa.
It was found that the TiC phase in the eutectic lamellar disappeared above the critical temperature of about 1750 K, but below the critical temperature the disappearance of TiC phase was hardly observed and TiO film was formed on the surface. The Mo matrix phase was not oxidized and was stable at all test temperatures, since its affinity for oxygen is lower than that for carbon and titanium.
It is presumed that at higer temperatures the disappearance process of TiC phase is controlled by the diffusion of carbon atoms through the matrix to the surface, and carbon and titanium atoms on the surface are removed by CO gas formation and TiO evaporation, respectively, but at lower temperatures the evaporation of TiO is so slow that the TiO film is formed on the surface.View full abstractDownload PDF (2159K) -
Toshio Shimoo, Tsutomu Isobe, Shigeru Ando, Hiroshi Kimura1986 Volume 50 Issue 2 Pages 168-175
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn the relation to the reduction of molten chromite ores with carbon, the rate of CrO reduction from aluminate slag melted in a graphite crucible has been studied by means of thermogravimetry under Ar atmosphere.
The reduction of CrO occurs at an interface between the slag and the carbon contained chromium melt which is formed on the crucible wall after contact of the molten slag with the graphite. The rate of CrO reduction is represented by the first-order-type rate equation. The reduction of CrO by solid carbon is a slow reaction, and the rate constant ranges from 10−4 to 10−3 kg/m2s at 1893 K. The constant increases with increasing cao/Al2O3 ratio. In some slags, the temperature dependence of the rate constant at lower temperatures is larger than that at higher temperatures. The reduction rate of CrO is affected by the geometry of the graphite crucible as a reductant. It is considered that the area of the slag in contact with the graphite depends strongly on the foaming of the slag in the early stage of the reduction. At low concentrations of CrO, the reduction is controlled by chemical processes.View full abstractDownload PDF (1294K) -
Hitoshi Taimatsu, Kazumi Ogino, Fumitada Nakatani1986 Volume 50 Issue 2 Pages 176-180
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe wetting behavior between liquid Ni-O alloys and MgO substrates was studied by using the sessile drop method in Ar-H2-H2O3 mixtures at 1873 K. The surface tension of the liquid Ni-O alloys was markedly lowered with the addition of a small amount of oxygen, and the contact angle decreased gradually with increasing oxygen content. The work of adhesion calculated from the surface tension and the contact angle slightly decreased with increasing oxygen content and reached a constant value beyond 0.01 mass%O in liquid Ni. Over the oxygen content ranges investigated, the MgO-NiO solid solution was formed at the solid-liquid interface. The above results and so far reported ones show that the form of the reaction product which produces a reduction of the contact angle in a liquid metal-oxygen/solid oxide system can be deduced from the phase diagram for the lowest oxide of the liquid metal-solid oxide system.View full abstractDownload PDF (1010K) -
Yoshinori Sasaki, Toshihiko Yamazaki, Akira Shimada1986 Volume 50 Issue 2 Pages 181-185
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe reaction of vanadium with phosphorus vapor was studied with particular reference to the layer structure of phosphide films, the relationship between reaction conditions and the products, and the kinetics and the mechanism of the reaction. A vanadium sheet was phosphidized in phosphorus vapor of 0.133 to 101 kPa at 1023-1373 K by means of a sealed-tube method.
\ oindentThe following conclusion was drawn:
(1) X-ray diffraction patterns and an electron microprobe analysis of the product phosphide films showed that the phosphide layer structure was VP1+x/VP/V2P/(V3P)/V.
(2) All the phosphidation reactions obeyed a parabolic rate law; hence, the rate-determining step was assumed to be a diffusion process. A marker experiment indicated that the component which diffused was not phosphorus but vanadium.
(3) The pressure dependence of the parabolic rate constant Kp resulted experimentally in the expression, Kp∝(vapor pressure of P4 molecule)1⁄4, at 1073 K. From the application of the mass action law to lattice defect equations of the VP formation, the phosphidation of vanadium was presumed to be controlled by diffusion of a cation vacancy with three trapped electron holes.
(4) The Kp was given by the following expression:
(This article is not displayable. Please see full text pdf.)
(5) The Kp of vanadium was considerably smaller than Kp-values for iron, nickel and chromium, which are the main constituent metals of stainless steel. Therefore, vanadium metal should be superior to these three metals with respect to phosphidation resistance.View full abstractDownload PDF (813K) -
Shigeaki Sugino, Hisato Hagiwara1986 Volume 50 Issue 2 Pages 186-192
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe activities of Zn in dilute solutions with molten Cu and Cu-Au alloys have been measured by the use of isopiestic method at temperatures 1423 K and 1373 K, from which the first and second order interaction parameters in molten Cu have been determined.
The activities of Zn in molten Cu-Zn and Cu-Zn-Au alloys exhibit negative deviation from Raoult’s law. Additions of a small amount of Au to the Cu-Zn binary alloys decrease the activity of Zn, the interaction parameter, εZnAu, being negative. The Cu-Zn binary liquid alloy seems to behave as subregular solution at dilute Zn concentrations. The activities of Zn in Cu-Zn-Au ternary liquid alloys are well expressed by a quadratic relation, lnγZn=lnZn°+εZnZnNZn+εZnAuNAu+ρZnZnNZn2+ρZnAuNAu2+ρZnZnAuNZnNAu, in the temperature and composition ranges studied in this investigation.View full abstractDownload PDF (880K) -
Teruo Tanabe, Makoto Ogawa, Zenjiro Asaki, Yoshio Kondo1986 Volume 50 Issue 2 Pages 192-200
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA dense plate of the mixed Ni-Fe sulfide of Ni3S2-3 mass%FeS was oxidized in a mixed O2-N2 gas stream at 923, 973 and 1023 K. The oxygen partial pressure was maintained at 2.0×104 Pa. The sample mass was increased during the oxidation, and the rate of mass increase was higher than that in the oxidation of Ni3S2. A very small amount of SO2 gas was evolved in the initial few hundred seconds, and no SO2 gas was evolved thereafter during the oxidation for 72 ks. SEM observation, EPMA and powder X-ray diffraction revealed that a multi-layered oxide film of Fe2O3, Fe3O4 and NixFe3−xO4 was formed on the sample surface.
In the early stage of oxidation, a thin layer of Fe oxide was rapidly formed, and the rate was controlled by the iron diffusion in the sulfide core. The activation energy was 190 kJ·mol−1. In the subsequent stage of oxidation, both the Fe oxide and NixFe3−xO4 layers grew in accordance with the parabolic rate law. The growth rate of Fe oxide was controlled by diffusion of iron through the oxide layer with the activation energy of 127 kJ·mol−1. The chemical diffusion coefficient of Ni in the NixFe3−xO4 layer was estimated as 10−16 to 10−17 m2·s−1. The Ni concentration in NixFe3−xO4 layer was increased with the reaction time, until the composition attained NiFe2O4. Thereafter, NiO was formed between the sulfide and NiFe2O4 in the oxidation at 1023 K.View full abstractDownload PDF (2620K) -
Michiya Okada, Yasunori Hayashi1986 Volume 50 Issue 2 Pages 201-207
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe surface effect on the hydrogen permeation in iron was discussed from the hydrogen charging and releasing characteristics measured by the electrochemical method, special attention being paid to the effect of arsenic addition to the catholyte.
The addition of arsenic to the catholyte changes the solution rate of hydrogen into iron under certain electrochemical conditions and causes the permeation property to change. Such a surface effect was separated from the permeation process by our oscillating method. Kinetic equations at the hydrogen entrance surface were solved, and the surface effect on the permeation in iron was discussed.View full abstractDownload PDF (857K) -
Toshio Suzuki, Yasunori Miyata, Tatsushi Kunieda1986 Volume 50 Issue 2 Pages 208-214
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSRipple marks formed at the surface of tin ingots are investigated in different types of casting processes, which are permanent mold casting, continuous casting and casting solidified rapidly on declined chill plates. Both average spacing and average depth of ripple marks are measured as functions of superheating in permanent mold casting, frequency of mold oscillation in continuous casting and casting speed. The average spacing and depth of ripple marks decrease with the increase of superheating in permanent mold casting. They increase with the decrease of mold oscillation frequency in continuous casting. In all experiments, the average spacing of ripple marks decreases proportionally to casting speed with power −0.34. The casting speed exponent of average depth is about twice as large as that of average spacing. A simple model for ripple mark formation has been proposed assuming the over-lap mechanism. Its prediction on the ripple mark spacing is in good agreement with the experimental results.View full abstractDownload PDF (1128K) -
Toshio Terasaki, Tetsuya Akiyama, Naohumi Kanematsu, Hiromi Sakamoto1986 Volume 50 Issue 2 Pages 215-222
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe time needed for the crack initiation, the rupture conditions and the relationship between the critical rupture stress (σImp)crR and the critical crack initiation stress (σImp)crI were studied using the Implant test method.
The time for the crack initiation was determined by the acoustic emission method (AE) and scanning electron microscopy (SEM).
A specimen unloaded just before the rupture occurrence was heated at 573 K for 1800 s in air. This heat treatment is called a blue line treatment, after which the crack surface becomes blue. The conditions for rupture of the specimen were discussed with the stress intensity factor calculated from the blue crack surface.
In order to study the relationship between (σImp)crI ard (σImp)crR, many commercial steels were tested, of which HAZ maximum Vickerss hardness varied from 205 to 636.
Results obtained are follows:
(1) The time for the crack initiation was less than 300 s.
(2) The fracture toghness of cold cracking is affected by the hydrogen content.
(3) The effect of hydrogen content on the fracture toughness of cold cracking is qualitatively explained with the Beachem’s model.
(4) (σImp)crI was able to be safely predicted by considering a stress by 100 MPa less than (σImp)crR.View full abstractDownload PDF (1566K) -
Teruo Takahashi, Yasuhiko Hashimoto, Shinichiro Omori, Koichiro Koyama1986 Volume 50 Issue 2 Pages 223-228
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDilute Cu-Zr alloys containing 0.39-1.95 mass%Zr were internally oxidized in the temperature range of 973-1323 K. The phases of dispersed oxides were identified by X-ray diffractometry, and the mean oxide particle sizes were measured by transmission electron microscopy. From X-ray diffractometry of the nitric-acid-treated insoluble residues, the oxide phases precipitated by internal oxidation were monoclinic and tetragonal ZrO2. The amount ratio of monoclinic ZrO2 to the total oxide was increased with the concentration of Zr at a constant internal oxidation temperature. In the case of alloys having the same concentration of Zr, the amount of monoclinic ZrO2 presented the minimum values at about 1223-1243 K. By transmission electron microscopy, it was revealed that large monoclinic ZrO2 particles were precipitated at grain boundaries of Cu and fine monoclinic and tetragonal ZrO2 particles were precipitated inside the Cu grains. The mean particle size of fine precipitates in Cu grains was increased with the distance from the surface. Any difference in the mean particle size of fine ZrO2 inside the Cu grains was not observed among the alloys having different concentrations of Zr, owing to the limitation of solution of Zr into Cu.View full abstractDownload PDF (1967K) -
Toshiro Kobayashi, Mitsuo Niinomi, Yoshihiro Koide, Kenji Matsunuma1986 Volume 50 Issue 2 Pages 229-235
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMany researches on ceramics have been reported, but no authorized method on impact test of ceramics exists at present.
In the present study, the absorbed energy of partially stabilized zirconia (PSZ) and SiC is analyzed in instrumented Charpy impact test and in static three-point bend test. Moreover, the influence of stress-induced phase transformation on the toughness in PSZ is investigated.
As a result, it is shown that the real fracture energy of PSZ is 57-59% of the total absorbed one and that the one of SiC is 38-56%. It is also shown that the amount of stress-induced phase transformation in Charpy impact test is more than the one in static three-point bend test. Furthermore, it is shown that a singular screwed loading is found in impact test of PSZ, which is due probably to an inertia effect and a stress-induced phase transformation.View full abstractDownload PDF (922K) -
Yoshio Morita, Takateru Umeda, Yasuo Kimura1986 Volume 50 Issue 2 Pages 235-241
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt is well known that Sm(Co,Cu,Fe)z (Z=near 7) alloys containing a proper quantity of Cu and Fe possess high coercivity and are used as superior permanent magnet materials. The Sm-Co-Cu-Fe quaternary phase diagram has not been studied. Therefore, the phase diagram near compositions of magnet alloys, and furthermore, relationships between phase transformations at high temperatures and coercivities were investigated. That is, Sm-Co-13 at%Cu-10 at%Fe and Sm-Co-9 at%Cu-18 at%Fe sections of the phase diagram were determined in the Sm content range from 10 to 15 at%. Furthermore, for various Sm(Co,Cu,Fe)z (Z=near 7) alloys, relationships between crystal structures after homogenizing treatment and coercivities after aging treatment were examined. The results are summarized as follows:
(1) The Sm2(Co,Cu,Fe)17 intermetallic compound (2/17 phase) has solubility from 10.5 to about 13.0 at%Sm at high temperatures. In the extended homogeneity region, the 2/17 phase possesses the hexagonal TbCu7 structure or the rhombohedral Th2Zn17 structure depending on the quantity of Cu and Fe. The limits of the former compositions are given by approximately 16≤Cu(at%)+0.73Fe(at%)≤23 and Cu(at%)+3>Fe(at%).
(2) The Sm(Co,Cu,Fe)z (Z=near 7) alloys quenched after homogenizing treatment, by which the 2/17 phase with TbCu7 structure is obtained, can possess high coercivity after the aging treatment.View full abstractDownload PDF (1375K) -
1986 Volume 50 Issue 2 Pages 242
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPlease see pdf. Wrong:7.2 ks at 773 K Right:3.6 ks at 1333 KView full abstractDownload PDF (23K)
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