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Volume 61, Issue 10
Displaying 1-17 of 17 articles from this issue
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Isamu Yamauchi, Hajime Ohata, Itsuo Ohnaka1997 Volume 61 Issue 10 Pages 1021-1030
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe formation behavior of a β-phase in the newly proposed Fe2Si5-B alloy with a small amount of Cu and their thermo-electric power were examined. The results are summarized as follows: The as-solidified structure of the Fe2Si5 based alloys with B and Cu was found to be mostly the α single phase by conventional X-ray diffractometry while a few B-rich and ε phase were observed by SEM. The β-phase formation rate in a conventional (FeSi2)99B1 alloy was increased by the addition of Cu, but still quite a long annealing period was necessary to attain the complete formation of β-phase. In the case of the Cu-added (Fe2Si5)99B1 alloy, the β formation was completed by annealing at 1073 K for 1.8×102 s. It is 100 times shorter than that in the binary Fe2Si5. The thermoelectric power of the newly proposed (Fe2Si5)99B1 alloy elucidated to be comparable with the conventional (Fe2Si5)99B1 alloy. The Si phase retained in the final state also found to cause no deterioration on the thermoelectric power.View full abstractDownload PDF (2904K) -
Keisuke Ishikawa, Yasuo Kobayashi, Toshiaki Kaneko, Toshinori Shibusaw ...1997 Volume 61 Issue 10 Pages 1031-1036
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe magnesium alloys are high in specific strength. Mg-Al-Zn alloys, in particular, have the excellent balance between strength and ductility. A magnesium alloy containing over 5% aluminum yields the cellular structures through the grainboundary reaction. AZ91D is modified for the heat treatment with killing the gaseous pore, since the strength is improved with the aging. The cellular reaction takes place heterogeneously along the grain boundary at the early stage of aging. The spacing of the lamellar, actually does not alter during the aging. The hardness has a linear relationship with the reciprocal spacing. The effect of the microstructures was observed on the mechanical properties; tensile and fatigue ones. Both the yield and tensile strengths increase in the aged structures, while the ductility decreases. The S-N curve appears to have little to do with the aging processes, though the fatigue crack propagation rate is fairly reduced for the aged materials. The homogeneous precipitation, however, would not bring large degradation in the fatigue properties. Although both homogeneous and heterogeneous structures can contribute to the strength of AZ91D, we observed the difference in the effect on the fatigue properties. The interface of the cellular precipitations could not be an effective barrier against the propagating fatigue crack.View full abstractDownload PDF (1083K) -
Setsuo Aso, Shoji Goto, Yoshinari Komatsu1997 Volume 61 Issue 10 Pages 1037-1043
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe structure of chromium white cast iron containing spheroidal graphite (SG-alloy) consists of three phases of M7C3 carbide, ferrous matrix and spheroidal graphite. The SG-alloy is produced by addition of Ce misch metal to a flaky graphite type of white cast iron (FG-alloy). A compression test was conducted at high temperatures for the SG-alloy. A shape of the stress-strain curves is classified into two types, that is, one type shows a shape with large work hardening up to a maximum stress level, which appears at lower temperatures below Tm/2 (700 K, Tm is the absolute melting temperature of the SG-alloy), and another one a shape with gradual work softening followed by the maximum stress, which appears at high temperature about Tm/2. The strain rate dependence of the maximum stress becomes remarkable at high temperatures above 873 K, and the values of strain rate sensitivity (m-value) is in the range from 0.11 to 0.14. The apparent activation energy (Q) for deformation is estimated to be from 300 to 400 kJ/mol in a higher temperature range above Tm/2, which is close to the activation energy for creep deformation of iron and steel. This suggests that the high temperature deformation process at high temperatures is controlled by the deformation of the matrix phase, while the strength of the SG-alloy is supported by the hard carbide phase. Spherodized graphite on the SG-alloy is effective to increase the strength below Tm/2, but it has no effect on the strength above Tm/2. This suggests that the high temperature deformation dose not depend on the morphology of graphite. The fracture surface after bending tests appears brittle below 673 K, and ductile above 873 K.View full abstractDownload PDF (1272K) -
Kuniteru Mihara, Takao Takeuchi, Hirowo G. Suzuki1997 Volume 61 Issue 10 Pages 1044-1049
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA small amount of carbon was doped into a Cu-15 mass%Cr in-situ composite to increase the strength of the material. It is found that in the as-cast state Cr dendrites exhibit a needle shape, which can be deformed into fibers much easier than the equiaxial ones.
A SIMS with the aid of thermodynamic simulation analysis suggests that Cr carbide exists as a nucleation site of Cr dendrites.
The composite has a tensile strength of 1200 MPa and an electrical conductivity of 38%IACS in the cold-worked state, and 960 MPa and 73%IACS after optimized aging treatment.View full abstractDownload PDF (935K) -
Fumiyoshi Kirino, Shigekazu Ohotomo, Nagatsugu Koiso1997 Volume 61 Issue 10 Pages 1050-1056
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSElectrochemical characteristics of single crystalline Mn-Zn ferrites with different MnO/ZnO ratios were studied when annealed in a vaccum and N2 atmospheres. The thermal treatment condition, which was similar to that used in the magnetic head fabrication process, consists three steps. The ferrite sample was first annealed at 1073 K for 1800 s in a vacuum, then at 873 K for 1800 s in N2 flow, and finally at 673 K for 1.08×104 s in N2 flow. The electrochemical characteristics of ferrite depended on the composition of ferrite (MnO/ZnO ratio). When the (MnO/ZnO ratio was 1.48, it showed the highest corrosion resistance. The electrochemical characteristics of the ferrite did not change, after passing the thorough annealing. When the cathode process of the Mn-Zn ferrite (MnO/ZnO ratio is 1.48) was compared with the anode process of the 9.8 at% Al-doped Fe-Ta-C film, it was found that any galvanic couple is not formed. These results show that electrochemical corrosion does not occur at the interface between the Mn-Zn ferrite and the Al-doped Fe-Ta-C film. The magnetic heads employing the single crystalline Mn-Zn ferrite and the Al-doped Fe-Ta-C film have a high resistance against corrosion.View full abstractDownload PDF (801K) -
Fumiyoshi Kirino, Shigekazu Ohotomo, Nagatsugu Koiso1997 Volume 61 Issue 10 Pages 1057-1063
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSInfluences of substrate materials and oxygen content in an annealing atmosphere on the corrosion resistance of Al-doped Fe-Ta-C magnetic thin films were studied by electrochemical methods. The reaction speed of pitting corrosion of Al doped Fe-Ta-C magnetic thin films prepared on a single crystalline Mn-Zn ferrite substrate was faster than that of the film prepared on a glass substrate. The high corrosion rate was associated with degradiation of the Fe (110) orientation, when the magnetic thin film was prepared on the ferrite substrate. When the Al-doped Fe-Ta-C films were annealed in an atmosphere containing oxygen, the pitting potential shifted to less noble potentials. The corrosion mechanism was studied by AES and ESCA. When the Al-doped Fe-Ta-C magnetic thin films were exposed to oxygen in the annealing atmosphere, Al in the alloys was preferentially oxidized and its concentration was reduced. As a result, the magnetic film became weak against pitting corrosion.View full abstractDownload PDF (675K) -
Ichiya Ishihara, Kenji Takahashi, Makoto Kawaguchi, Fujio Ishii, Mitsu ...1997 Volume 61 Issue 10 Pages 1064-1069
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe deoxidation equilibrium of aluminum in liquid cobalt has been measured at the temperature ranges from 1873 to 1973 K using alumina crucibles with a view to understanding the equilibrium between aluminum and oxygen in liquid cobalt.
The temperature dependence of the deoxidation constants, KAl(=aAl2·aO3⁄aAl2O3(s)), for the deoxidation reaction in liquid cobalt, i.e.:
(This article is not displayable. Please see full text pdf.)
\ oindentwas found to be:
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\ oindentwhile the effect of temperature on the deoxidation product, KAl′(=[%Al]2[%O]3) and the effect of aluminum on the activity coefficient of oxygen in liquid cobalt were determined by the expressions:
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Shoichirou Taira, Noboru Utsunomiya, Yasuyuki Yamasaki, Sigenobu Yamag ...1997 Volume 61 Issue 10 Pages 1070-1076
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe solubilities of nitrogen in CaO-SiO2-Al2O3 slags were measured using N2-H2 gas or silicon nitride ceramics at 1823 K. Moreover Vickers hardness of the quenched slags was measured. Based on these results, the dissolution mechanism of nitrogen into the slags was discussed.
The nitride capacity measured by an equilibrium between N2-H2 gas and slag under a given partial pressure of oxygen decreased with increasing SiO2 content. This result suggested that nitrogen dissolved in the slags by exchanging reaction between oxygen ion and nitrogen. On the other hand, the nitride capacity by an equilibrium between silicon nitride ceramics and slag was 102 to 104 times larger than that from gas-slag equilibrium. Although the nitride capacity was calculated assuming that silicon nitride decomposed, it was not in agreement with that from gas-slag equilibrium. Therefore it was estimated that the dissolution mechanism of nitrogen using silicon nitride ceramics was different from that obtained by nitrogen gas.
Vickers hardness of the solidified slag after silicon nitride dissolution decreased with increasing SiO2 content and this tendency was the same as the influence of silica on nitrogen solubility. This suggested that network formation in the slag was strengthened by the dissolution of silicon nitride, which was estimated to proceed with the formation of complex network between Si-N (or Al-N) and oxide.View full abstractDownload PDF (870K) -
Tadaaki Amano, Toshiki Watanabe, Kaoru Michiyama1997 Volume 61 Issue 10 Pages 1077-1085
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSHigh-temperature oxidation behavior of Fe-20Cr-4Al alloys with 3, 35, 53, 104 and 171 ppm of sulfur was studied for 18.0 ks in oxygen at 1273, 1373, 1473, 1573 and 1673 K by mass change measurements, observation of surface appearance of the alloys, X-ray diffraction, scanning electron microscopy and electron probe microanalysis. The mass changes of the alloys increased roughly with increasing oxidation temperature. However, the mass changes of the alloys with 35 and 53 ppm of sulfur at 1473 K and with 35, 53 and 104 ppm of sulfur at 1573 K showed negative values. This fact was in good agreement with spalling of the oxide on the alloys. The oxides on all the alloys were only α-Al2O3 at any oxidation temperature. Oxide morphology on the alloys with 35, 53, 104 and 171 ppm of sulfur changed from convoluted to planar with increasing oxidation temperature. On the other hand, the oxide on the alloy with 3 ppm of sulfur was planar at any oxidation temperature. This result suggested that spalling of the oxide on the alloys was related to the formation of convoluted oxide morphology. After oxidation at 1473 and 1573 K, the spalling of oxide on the alloys with 104 and 171 ppm of sulfur was decreased remarkably as compared with that on the alloys with 35 and 53 ppm of sulfur. The oxide adherence of these alloys with 104 and 171 ppm of sulfur may be attributed to the formation of Cr sulfide at the oxide/alloy interface.View full abstractDownload PDF (3095K) -
Noriyoshi Yuge, Kazuhiro Hanazawa, Kohji Nishikawa, Hisaei Terashima1997 Volume 61 Issue 10 Pages 1086-1093
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSVacuum refining under the atmospheres of 8.0×10−3∼3.6×10−2 Pa was applied for removing phosphorus, aluminium and calcium in metallurgical grade silicon (MG-Si) at 1722∼1915 K, and the low-pressure refining under the atmospheres of 4.0∼190 Pa was applied for removing phosphorus at 1733∼1823 K.
The phosphorus and calcium contents decreased under 0.1 mass ppm by vacuum refining at 1915 K. The removal rates of these elements from molten silicon were roughly expressed by the equations of the first order. The apparent rate constants were expressed as follows;
(This article is not displayable. Please see full text pdf.)
The activation energy of removing phosphorus, aluminium and calcium from molten silicon were estimated to be 130 kJ/mol for phosphorus, 186 kJ/mol for aluminium and 147 kJ/mol for calcium, respectively. It has been demonstrated that the overall removing rates of these elements are controlled by the diffusion in molten silicon and the evaporation from the silicon surface.
The phosphorus content was also decreased by the low-pressure refining. The removal rate of phosphorus was roughly expressed by the equation of the first degree. It increased with decreasing atmospheric pressure, but did not change with increasing melting temperature.
The evaporation rate of silicon observed by vacuum refining was expressed as follows:
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Noriyoshi Yuge, Yasuhiko Sakaguchi, Hisaei Terashima, Fukuo Aratani1997 Volume 61 Issue 10 Pages 1094-1100
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPurification of silicon by directional solidification under the solidification rate from 5.9×10−6 to 2.2×10−5 m/s was applied for removing aluminium, iron and titanium. Aluminium content was decrease of up to the range of two to three orders from about 100 mass ppm. Iron and titanium contents were decreased under 0.1 mass ppm from about 300 and 20 mass ppm, respectively. Aluminium content profile in solidified silicon could be expressed by the Sceil’s equation and Burton’s equation. Iron and titanium content profiles could not be confirmed by those equations, because detective values limit for iron and titanium were higher than the calculated content.
High initial impurity contents lowered efficiency for removing impurity contents in silicon. This was assumed that the stability of planar solid/liquid interface was broken by a low temperature gradient of the liquid phase according to the constitutional supercooling theory.
SOG-Si which was experimentally produced through the direct reduction process and the molten purification process showed low impurities contents of less than 0.1 mass ppm of aluminium, iron and titanium. Conversion efficiency of the multicrystalline cell made by those silicon had almost the same performance as made from electrical-grade silicon.View full abstractDownload PDF (619K) -
Yasunori Miyata, Yukio Kume, Manabu Fujimoto, Tomoji Morita1997 Volume 61 Issue 10 Pages 1101-1107
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSRadius of curvature of the tip of needle dendrite, which grows just after the break-down of planar interface, is studied in the unidirectional solidification of succinonitrile-acetone alloy. The measured tip radius of curvatur is very close to the one given by the marginal stability proposed by Langer and Müller-Krumbhaar.View full abstractDownload PDF (1205K) -
Shozo Inoue, Hitoshi Uchida, Takaaki Ohba, Keiji Koterazawa, Akiyoshi ...1997 Volume 61 Issue 10 Pages 1108-1114
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe process of rf reactive magnetron sputtering is suitable for depositing TiN films, because of its applicability for large-area processing. This process, however, shows the so-called hysteresis when the reactive gas is controlled by constant flow rate, which leads to a relatively poor reproducibility.
In this paper, it is shown that the closed-loop nitrogen flow control by plasma emission monitoring (PEM) provides a stable reactive sputtering under a wide range of nitrogen partial pressure. The influence of the nitrogen partial pressure on the Ti-N film composition, crystallographic structure and resistivity was also investigated. The Ti-N films deposited at the nitrogen partial pressure of 2∼5×10−3 Pa revealed the minimum resistivity and appeared to be stoichiometric TiN. The PEM control system makes it possible to stably control this range of nitrogen partial pressure. This system also provides high rate film processing.View full abstractDownload PDF (610K) -
Mitsuyoshi Shimaoka, Itsuo Ohnaka, Isamu Yamauchi, Munehiko Maeda1997 Volume 61 Issue 10 Pages 1115-1121
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThis paper presents the effects of addition of Be on the spinnability of Co-Cu alloys in a concentration range from 5 to 97 at%Cu in the In-Rotating-Water-Spinning process, the solidification structure and mechanical properties of obtained wires. Wires longer than 1.5 m with high roundness in the cross-section could be produced when 5 at%Be was added. To produce a long wire, it was important to quickly eject the melt through a nozzle with high reduction before heavy reaction of the molten alloy with the quartz nozzle. In the case of 5∼50 at%Cu alloys, finer dendritic structures of Co-rich phase caused by rapid cooling were observed and the secondary dendrite arm spacing varied inversely as about the cubic root of cooling rate. The secondary dendrite arm spacing decreased with increasing Cu concentration and such a tendency agreed roughly with the calculated result. In the case of 60∼80 at%Cu alloys, granular structures separated into the Co-rich and Cu-rich phases were observed. Because these structures are formed by the result of undercooling below the liquid immiscibility temperature through rapid cooling, it is estimated that the undercoolings of about 80 K or more occur in this process. In the case of 90 and 97 at%Cu alloys, dendritic structures of the Cu-rich phase were observed. The elongation of rapidly solidified wire was about 20% for the 5 at%Cu wire and decreased with increasing Cu concentration. In the case of the separated two-phase structure, the elongation was lower than about 5%, but the ductility was high enough to be bent through 180 degrees without fracture. The tensile strength was in the range from 300 to 600 MPa.View full abstractDownload PDF (1231K) -
Yoshimitsu Okazaki, Kenji Kyo, Yoshimasa Ito, Tetsuya Tateishi1997 Volume 61 Issue 10 Pages 1122-1131
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe micromotion between the bone and the implant gives rise to metallic ion release. This results in the loosening of the stem and thus gives rise to pain. The effect of frictional load on the corrosion resistance by the anodic polarization test of new Ti alloys against apatite and alumina ceramics in Eagle’s medium and in 1% lactic acid solutions was investigated. It was observed that the corrosion potential decreased under the frictional condition for Ti alloys, but the effect was little under the frictional condition for a Co-Cr alloy and SUS316L. The passive film is broken and formed during applying friction and hence a variation in the current density was seen. The current density becomes higher during friction than static conditions for all the alloys. The fluctuational width of the current density (Maximum-Minimum value) during friction is much broader for Ti alloys as compared to that of the Co-Cr alloy and SUS316L. The fluctuation width was observed in both activity and passivity zones for Ti alloys. However, the fluctuational width was observed in the passivity zone for the Co-Cr alloy. Among the Ti alloys, during friction against apatite, the current density was low for the Ti-Zr alloy even at a high potential and also the fluctuational width of the current density was narrow as compared to other Ti alloys. Hence, the Ti-Zr alloy is superior to other Ti alloys. The effect of the lateral speed was also negligible for the Ti-Zr alloy as compared to that of other Ti alloys. The corrosion resistance during wear conditions, change with the materials used as disk and pin, frictional load, potential zone and with the pH of the solution, the wear properties for Co-Cr and SUS316L were much superior as compared to Ti alloys. The Ti-Zr alloy showed excellent wear properties as compared to other Ti alloys.View full abstractDownload PDF (911K) -
Satoshi Semboshi, Hideki Hosoda, Shuji Hanada1997 Volume 61 Issue 10 Pages 1132-1138
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSome Nb3Al-base alloys are known to be pulverized by holding in hydrogen atmosphere. The pulverization by hydrogenation is expected to be applied to preparation of fine powder with high quality and low cost. The purpose of this study is to investigate the mechanism of pulverization by hydrogenation of Nb3Al-base alloys with or without second phases. Alloys prepared were Nb3Al single phase alloy (Nb-21 mol%Al alloy: Nb-21Al), and two phase alloys including Nb solid solution (Nb-16 mol%Al alloy: Nb-16Al) and Nb2Al (Nb-28 mol%Al alloy: Nb-28Al). They were heat-treated at 1473 K for 86.4 ks in a vacuum atmosphere. After surface treatment, hydrogenation was carried out under hydrogen pressure from 0 to 3.4 MPa at 313 K and 353 K. Powder formed by hydrogenation was observed using a scanning electron microscope. Identification of phases and measurement of lattice constants before and after hydrogenation were carried out by X-ray diffraction. It is clearly seen that both the two phase alloys, Nb-16Al and Nb-28Al, are pulverized by hydrogenation. On the other hand, the single phase alloy, Nb-21Al, is not pulverized under the experimental conditions. Then, it is assumed that the existence of the second phases accelerates the pulverization by hydrogenation. Both lattice constants and volumes increase remarkably through hydrogenation and no hydric compound is recognized. It is concluded that the pulverization of Nb-16Al and Nb-28Al is caused by large strain energy generated by the difference in lattice expansions between Nb3Al and Nb solid solution, and between Nb3Al and Nb2Al in pulverization by hydrogenation. In the case of single phase alloy of Nb-21Al, little strain energy is generated through hydrogen absorption, that leads to difficulty in pulverization under the experimental conditions.View full abstractDownload PDF (1004K) -
Kouichi Higuchi, Hironobu Fujii, Shin-ichi Orimo, Kazuhiko Terata1997 Volume 61 Issue 10 Pages 1139-1146
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSComposite materials were prepared by disproportionation reaction of Y5Mg24 and Y5Mg22.5Ni1.5 with hydrogen in the temperature range from 24 to 400°C. The structural features were examined by using X-ray diffraction technique, SEM- and TEM- observations, while the hydriding and dehydriding properties were studied by using a Sieverts’ method and a thermo-gravimetry analysis.
The results obtained are summarized as follows: (1) At the first hydriding process under 400°C and 3 MPa H2, Y5Mg24 and Y5Mg22.5Ni1.5 were respectively decomposed into two and three main phases of YH3 and MgH2, and YH3, MgH2 and Mg2NiH4. The external region of products was covered by YH3 and lamellar-like YH3/MgH2, and the internal regions were composed of MgH2 and YH3 with the size of several micrometers for Y5Mg24, and MgH2, YH3 and eutectic mixture MgH2/Mg2NiH4 with the size of several hundred nanometers for Y5Mg22.5Ni1.5, respectively. (2) Even at low temperatures below 100°C, Y5Mg22.5Ni1.5 was hydrogenated and decomposed into YH2, MgH2, Mg2NiH0.3 and a small amount of nonreactive Y5Mg22.5Ni1.5 with nanometer size. (3) After several cycles of hydriding - dehydriding process, the products became to show stable hydriding properties and maximum hydrogen content reached 3.8 mass% at 302°C within 10 minutes for Y5Mg22.5Ni1.5. (4) The dehydriding reaction from the hydrogenated Y5Mg24 occurred at 350°C, whereas the dehydriding reaction for all the hydrogenated Y5Mg22.5Ni1.5 in the temperature range from 24 to 400°C started to occur arround 250°C, which is close to the dehydriding temperature of Mg2NiH4.View full abstractDownload PDF (887K)
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