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Volume 61, Issue 11
Displaying 1-18 of 18 articles from this issue
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Isao Tochigi, Tsunemichi Imai, Kyosuke Ai1997 Volume 61 Issue 11 Pages 1147-1152
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSβ-Si3N4 whisker reinforced 6061 aluminum alloy composite fabricated by squeeze casting was extruded with the extrusion ratios of R=44 and R=100 at 773 and 803 K. The tensile strength and superplastic characteristics of the composite were investigated. The composite indicates the tensile strength of 400 MPa at room temperature and about 250 MPa at 573 K. The composite extruded with R=100 exhibits the m value of 0.31 in the strain rate range from 0.01 to 1.07 s−1 and the total elongation of 173% at the strain rate of 0.02 s−1. The whisker reacted with 6061 aluminum alloy so as to synthesize AlN and make Si soluble to the matrix at interfaces. Therefore, an interfacial sliding in semi-solid condition might occur during superplastic deformation. The grain sizes of the composite heated up at 818 K and deformed superplastically was under 3 μm which is almost the same size of the composite fabricated by PM method before extrusion. The difference of superplastic characteristics in the composite between squeeze casting and PM method routes might be associated to subgrain behavior.View full abstractDownload PDF (1110K) -
Naoyuki Kanetake, Takahisa Kaneko, Takao Choh1997 Volume 61 Issue 11 Pages 1153-1159
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCold rolling and subsequent annealing processes were investigated to fabricate SiC particle reinforced pure aluminum composite sheets. Composite bars with different volume fractions of particles were prepared by a powder extrusion and cold rolled in various reductions and subsequently annealed at various temperatures. The limit rolling reduction, that is the maximum reduction at which no cracks are observed in the rolled sheet, was measured for the composites. The effects of cold rolling reduction and annealing temperature on the tensile properties of the composite sheets were evaluated and compared with those of unreinforced pure aluminum sheets.
The composite sheet with a lower SiC volume fraction than 10% can be successfully cold rolled in higher reduction than 90%. The proof stress and tensile strength of the composite sheets rolled in higher reduction than 60% are hardly changed with the rolling reduction, though those of the unreinforced pure aluminum sheets are increased with the reduction. The proof stress and tensile strength of rolled pure aluminum are rapidly decreased and its elongation is rapidly increased by subsequent annealing at 548∼573 K. But those properties of the composite sheets are only gradually varied with subsequent annealing temperature.View full abstractDownload PDF (1140K) -
Seungkyun Ryu, Junichi Kaneko, Makoto Sugamata1997 Volume 61 Issue 11 Pages 1160-1167
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSiC whisker reinforced composites with a pure magnesium matrix were fabricated by two different processing routes, high pressure casting and powder metallurgy. The structures and mechanical properties were compared on the obtained composites after hot extrusion. The extruded composites by the P/M process showed slightly higher average aspect ratio and less uniform distribution of SiC whiskers than those by high pressure casting. Increases in hardness and elastic modulus with the whisker Vf were observed to be the same for both composites. However, the P/M composites showed much less increases in tensile strength than those by high pressure casting. In the P/M composites, decohesion at the matrix-reinforcement interface occurred under tensile load. No chemical reaction was observed between the matrix and SiC whiskers in P/M composites, whereas surface oxide of whiskers reacted with magnesium melt in high pressure cast composites. Such an interface reaction is necessary for strong matrix-reinforcement cohesion, and thus the P/M process is considered to be unsuitable for fabrication of SiCw/Mg composites.View full abstractDownload PDF (1151K) -
Akio Hirose, Shinji Fukumoto, Kojiro F. Kobayashi1997 Volume 61 Issue 11 Pages 1168-1174
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn the present work, we have investigated the role of interlayers in bonding continuous SiC fiber reinforced Ti-6Al-4V composites and have applied step joint forms and scarf joint forms to bond the composites.
The composites were successfully diffusion bonded to themselves using a matrix interlayer. The joint strengths increased with thickness of the interlayer. In a composite with a fiber volume fraction (Vf) of 30 vol%, the joint strengths of 800 to 850 MPa, which were equivalent to a strenght of the composite to the Ti-6Al-4V joint, were obtained using interlayers more than 80 μm in thickness. Although the joint strengths decreased with increasing Vf of the composites, they were 150 to 200 MPa higher than the values simply calculated form area fractions of the matrix at bonded interfaces. This is thought to be caused by triaxially constraining plastic deformation of the matrix near the fibers.
Pseudo-step joints of a 10-ply composite (Vf=30 vol%) were fabricated with a varying number of steps and those strengths increased with the number of steps. A step joint with 10 steps showed 90% tensile strength of the composite. Scarf joint forms were applied to diffusion bonding of the composites to a Ti-6Al-4V plate and to themselves. The composites (Vf=30 vol% and 45 vol%) to Ti-6Al-4V joints were fractured in the Ti-6Al-4V plate. The composite (Vf=30 vol%) to composite joints had a maximum strength of 1380 MPa corresponding to approximately 80% tensile strength of the composite.View full abstractDownload PDF (1079K) -
Takahiro Murata, Tetsutoshi Awamura, Kenji Morinaga1997 Volume 61 Issue 11 Pages 1175-1180
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAbsorption spectra of Cu+ and Cu2+ were measured for silicate, borate, and phosphate glasses doped with 0.1 mol%Cu2O. The molar extinction coefficient at the peak wavelength of the 2B1g→2B2g transition of Cu2+ was used as a parameter showing the relative content of Cu+ ions in glass samples. Compositional dependence of Cu+-Cu2+ redox was examined using compositional parameter B which represented the average basicity of glasses. We estimated that glass composition within the B range of 0.2-0.3 is suited for Cu+-doped tunable glass laser because the absorption of Cu2+ was minimized at this range. In borate and phosphate glasses, the Cu+ ion was chemically stabilized by the addition of alumina. We concluded that the glass composition suitable for Cu+-doped tunable glass laser materials is 10Na2O·80B2O3·10Al2O3 on the basis of fluorescence measurement.View full abstractDownload PDF (567K) -
Yoshinobu Tahara, Noriyuki Kuwano, Kensuke Oki1997 Volume 61 Issue 11 Pages 1181-1187
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe temperature derivative of electrical resistivity, αR, in an FeCo alloy was measured with a constant rate of increasing temperature, and the residual resistivity was also measured at the liquid-nitrogen temperature as a function of quenching temperature. We proposed a kinetic equation for αR, which includes the change of vacancy concentration and the degree of order S with the annealing time, and then analyzed the experimental results by using the equation. It was found that the electrical resistivity and the residual resistivity decrease approximately in proportion to S2. The electrical resistivity by magnetic scattering, however, hardly decreases with increasing S. Further, αR caused by only the ordering, or ΔαR, was estimated by eliminating other effects, namely the magnetic and phonon scattering effects in disordered alloys. The observed ΔαR was analyzed by our kinetic equation, and the behavior of ΔαR on isochronal ordering was interpreted satisfactorily.View full abstractDownload PDF (761K) -
Koji Tanoue, Yoshihiko Mukaiyama1997 Volume 61 Issue 11 Pages 1188-1197
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSScanning electron microscopic (SEM) observation is made to examine the geometry of bubbles in P/M tungsten fine wires after their secondary recrystallization is completed. The effect of the geometrical properties of bubbles on abnormal grain growth is then investigated using a Monte Carlo computer simulation technique. While bubbles, with the mean diameter of 23 nm, are present at grain boundaries with a high number density of ρ=1013 m−2, the number density of bubbles inside a grain is about 5% of ρ. As the specimens are annealed, ρ decreases rapidly and thereby the mean bubble diameter increases after many small bubbles form at grain boundaries. The latter is thought to be the process of bubble formation caused by the increase in the internal pressure of potassium gas, while the former is considered to be the coarsening process of large bubbles caused by the diffusion of potassium along grain boundaries from smaller to larger bubbles. Moreover, it can be concluded from the results of the computer simulation that the final abnormal grain structure is very much influenced by the mutual positional relation between the arrays of bubbles and the potential abnormal grains, being indirectly influenced by the bubble intervals in an array, the growth of bubbles, the number of initial abnormal grains and so on.View full abstractDownload PDF (1308K) -
Kazuto Hamaishi, Hidekazu Sueyoshi, Takayuki Shiomizu, Yoshihisa Ohzon ...1997 Volume 61 Issue 11 Pages 1198-1205
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThree types of austenitic stainless steels, SUS304, SUS316 and SUS310, were preheated in air in a temperature range of 293 to 1273 K after diamond-polishing or #120 emery paper-polishing, followed by nitriding in NH3 gas at 843 K for 20 h. The influence of atmospheric preheating on nitriding behavior was examined in connection with the composition of the surface film.
In the case of diamond-polishing, atmospheric preheating in the temperature range of 673 to 1023 K for 1 h in SUS304 steel and in the temperature range of 293 to 1023 K for 1 h in SUS316 and SUS310 steels result in the formation of a uniformly nitrided layer. The depth of nitrided layer reached a maximum at the preheating temperature of about 1000 K in SUS304 steel, in the preheating temperature range of 800 to 1000 K in SUS316 steel and at the preheating temperature of about 800 K in SUS310 steel, respectively. The nitriding reaction was promoted with increasing preheating time in SUS304 and SUS316 steels, but it was independent of preheating time in SUS310 steel. The nitriding reaction after emery paper-polishing is inferior to that after diamond-polishing.
It was confirmed that gas nitriding of austenitic stainless steels was possible without any chemical treatment, when atmospheric preheating which forms the surface film consisting mainly of iron oxide at the surface and containing a low concentration of Cr2O3 and a high concentration of FeO in the interior was applied.View full abstractDownload PDF (795K) -
Ryoichi Monzen, Takaharu Echigo1997 Volume 61 Issue 11 Pages 1206-1210
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe growth of BCC Fe-Co boundary particles has been examined for various [011] symmetric tilt and twist boundaries in Cu-Fe-Co bicrystals aged at 723, 748 and 773 K. Except for some specific tilt and twist boundaries in bicrystals aged at 773 K, the particle growth obeys a relationship of the form \barrn=Kt (where \barr is the mean radius, K is a constant and t is the aging temperature) with n=4, as predicted by growth theories of boundary particles. For the special boundaries, n has a value between 3 and 4. The result can be interpreted by considering the relative amount of solute movement along the boundary by grain-boundary diffusion and through the matrix by bulk diffusion. It is found that, for the two types of grain boundary, the activation energy for the particle growth on a boundary shows a good correlation with the energy of the boundary. That is, a lower-energy boundary has a lower diffusivity.View full abstractDownload PDF (465K) -
Satoru Ishihara, Mikio Kondoh, Kazuhiko Itoh1997 Volume 61 Issue 11 Pages 1211-1219
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAl-17Si-4.5Cu-0.5Mg-(0∼6)Fe-(0∼2)Mm (Mm: misch metal) rapidly solidified powder metallurgy (RSP) alloys were prepared by the hot extrusion method. High temperature tensile properties and deformation behavior of these alloys at 773 K were investigated. In the Al-17Si-4.5Cu-0.5Mg alloy with various Si particle sizes, typical superplastic behavior is obtained at the same strain rate of 1×10−2 s−1. The superplastic tensile elongation increased with decreasing Si particle size. With increasing Fe content, the average matrix grain size decreased and the optimum superplastic strain rate increased, but the maximum tensile elongation decreased. The grain-size sensitivity on the superplastic strain rate is about 3, as that of other superplastic Al alloys. Misch metal addition has a significant effect of retardation of coarsening of matrix grains by uniformly precipitated Al2(Si, Cu)2RE (RE: Lanthanoid) particles finer than compounds including Fe, and the maximum tensile elongation was obtained at a high strain rate of 1×100 s−1. It is generally concluded that the superplastic elongation of Al-Si RSP alloys is affected by the size of dispersing particulates.View full abstractDownload PDF (1677K) -
Masayuki Itagaki, Takashi Mori, Kunihiro Watanabe1997 Volume 61 Issue 11 Pages 1220-1227
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCurrent oscillation of copper electrode in acidic chloride solution was investigated using the channel flow electrode system. Phase space analysis of the oscillation shows the strange attractor and, moreover, the vending and streching behavior in the Poincare sections. The largest Lyapunov exponent of the current oscillation was positive. The above-mentioned results indicated that the oscillation was governed by deterministic chaos. Some reaction models of the two-valiable system were examined to represent the current oscillation. The current oscillation could be explained by the non-linear dissolution rate of the adsorbed intermediate, which was cubic autocatalysis.View full abstractDownload PDF (668K) -
Masayuki Kondo, Tatsuo Morimoto1997 Volume 61 Issue 11 Pages 1228-1233
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAs an oxidation protection system for C/C composites, SiC coating by conversion method (conv-SiC layer) is very important. In order to obtain a clear understanding of SiC conversion mechanisms, microstructure of the conv-SiC layers on carbon substrates was inspected and microstructural evolution process was discussed from a thermodynamical point of view. As carbon substrates, isotropic graphite and C/C composites were selected. conv-SiC is formed through a reaction between C of the substrates and SiO gas. SiO gas is mainly produced through reaction between Si in a raw material for SiC conversion and CO gas from SiC formation reaction. A dominant transportation mechanism of SiO gas and CO gas during SiC conversion is assessed to be gaseous diffusion through micropores with a diameter of about 200 nm in the growing conv-SiC region or surface diffusion on the wall of the micropores instead of solid-state diffusion. A precise microstructural analysis of the conv-SiC layer and SiC/C interface suggested its excellent adhesion characteristics with the substrates.View full abstractDownload PDF (1245K) -
Hiroshi Ono, Tokuo Shimizu, Yoshio Shijo1997 Volume 61 Issue 11 Pages 1234-1240
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe separation and determination of trace amounts of Ti, Zr, Mo, Sn and Hf in Ni were studied. After the sample was dissolved with nitric acid, Ti, Zr, Mo, Sn and Hf were separated from Ni by extracting into benzene with N-benzoyl-N-phenylhydroxylamine (BPA) and subsequently back-extracted into nitric acid for the determination by ICP-AES or ICP-MS. The recoveries of Ti, Zr, Mo, Sn and Hf were satisfactory throughout the extraction with 4.0×10−2 mol·dm−3 BPA in benzene from 1.0 mol·dm−3 nitric acid-0.1 mol·dm−3 trichloroaceticacid solution and the back- extraction with 60%nitric acid. The separation factors (SM=DM⁄DNi, D=distribution ratios) of Ti, Zr, Mo, Sn and Hf from Ni were 9.9×103 for Ti, 3.2×104 for Zr, 3.2×104 for Mo, 1.3×103 for Sn and 4.0×104 for Hf. The recoveries of Ti, Zr, Mo, Sn and Hf decreased somewhat with increasing the added amount of Ni. The detection limits by ICP-MS were found to be 0.031 μg·g−1 for Ti, 0.046 μg·g−1 for Zr, 0.014 μg·g−1 for Mo, 0.7 μg·g−1 for Sn and 0.006 μg·g−1 for Hf using 0.5 g of Ni sample. The proposed method was applied to analysis of the real sample.View full abstractDownload PDF (535K) -
Tokiko Nakagawa, Motoi Hara, Kiyoshi Imai1997 Volume 61 Issue 11 Pages 1241-1248
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe hot corrosion behavior of SiC specimens prepared by solid phase sintering and CVD was examined in molten Na2SO4 at 1223 K under argon and oxygen atmospheres. Measurement of mass change, and surface observation and analysis of specimens after corrosion experiment were carried out. Particular attention was paid to the effect of sintering additives in SiC and gas atmosphere on the corrosion behavior. The SiC prepared by CVD showed the best corrosion resistance in the molten salt under argon atmosphere. For the SiC specimens prepared by solid phase sintering, the SiC containing lower content of sintering additives showed better corrosion resistance than that containing higher content of sintering additives. Many small holes were observed on the SiC specimens prepared by solid phase sintering after corrosion experiment. However, the SiC specimens did not corrode under oxygen atmosphere regardless of the kinds of specimens. The formation of cristobalite SiO2 film was observed on the specimen surfaces after corrosion experiment under oxygen. The pre-oxidation treatment led to a stop of corrosion for the SiC specimens with and without sintering additives in the molten salt even under argon atmosphere. The formation of cristobalite SiO2 film was also observed for the pre-oxidized specimens after the corrosion experiment. Consequently, it was found that the SiO2 film formed on SiC stopped corrosion of SiC in molten Na2SO4.View full abstractDownload PDF (1354K) -
Eiji Tada, Kazuhiko Noda, Shinji Kumai, Tooru Tsuru1997 Volume 61 Issue 11 Pages 1249-1254
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCorrosion fatigue tests of a commercial iron were carried out in a borate buffer solution containing sodium chloride at a constant passive potential. In order to detect crack initiation and quantify the extent of corrosion fatigue damage, the polarization current responding to the strain cycles has been studied. From this current, the current amplitude and the phase shift between the current and the strain were calculated. By analysis of these parameters, crack initiation was detected in such an early stage of about 10% of the fatigue life. The extent of the surface damage was detected from the distortion of the wave form due to the higher harmonics components. The corrosion fatigue process was investigated by the polarization current behavior.View full abstractDownload PDF (868K) -
Shouhei Hata, Toshio Narita1997 Volume 61 Issue 11 Pages 1255-1259
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFracture strength of Si3N4 ceramics joined to stainless steels with a Ag-Cu-Ti filler and a Ni(0.02∼0.5 mm)/W/Ni interlayer was investigated as functions of the ceramic strength and Ni-interlayer thickness.
For the joints with a 1500 MPa ceramics fracture strength of the joints increased monotonously with decrease of Ni-interlayer thickness from 300 MPa at 0.5 mm to 660 MPa at 0.02 mm. For the joints with 800 and 1100 MPa ceramics, however, the fracture strength decreased rapidly when the Ni-interlayer was thinner than 0.25 mm. This degradation seems to be due to cracks formed during a bonding process. The effect of ceramic strength on the fracture strength of ceramic/metal joints was hardly observed when these pre-cracks were eliminated from the joints.
It was suggested that the bonding layer plays decisive role in the fracture strength of ceramic/metal joints in addition to the thermal residual stress, irrespective of the ceramic strength itself.View full abstractDownload PDF (1086K) -
Kunimasa Takeshita, Satoshi Sakamoto1997 Volume 61 Issue 11 Pages 1260-1267
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTi-10 mass%Zr alloy was resistance brazed with laminated filler metals composed of Ni-Cu and Cu-Be alloy foils by varying the method of cooling. The effect of rapid cooling on the tensile strength of the joints was investigated in connection with the brazed microstrucrtures.
The joint with the highest tensile strength of 642 MPa is obtained by using the laminated filler metal of a 50 μm thick Ni-Cu alloy foil interposed between 15 μm thick Cu-Be alloy foils and by subjecting to rapid cooling, the rate of which is about 400 K/s. The brazed microstructure of the joint exhibits that the stabilized β-Ti within the filler metal region interconnects the base metals, which causes a characteristic of its high joint strength.View full abstractDownload PDF (1197K) -
Toshitada Shimozaki, Takahisa Okino, Masahiro Yamane1997 Volume 61 Issue 11 Pages 1268-1269
Published: 1997
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (205K)
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