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Volume 59, Issue 11
Displaying 1-18 of 18 articles from this issue
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Ken Atagi, Yoshiharu Ootani, Yosihiro Okumoto, Kouichi Maruyama1995 Volume 59 Issue 11 Pages 1087-1094
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFatigue crack initiation along boundaries was studied by using aluminum bicrystals. The bicrystals were grown by the Bridgman method to have three different inclinations of 0, π⁄36 and π⁄15 rad between the grain boundary and the primary slip plane. They were tested by a bending fatigue machine under strain amplitudes of 0.13, 0.08 and 0.05%, and the effects of the strain amplitudes on crack initiation and propagation were examined. Fatigue cracks are nucleated along the grain boundaries at all the strain amplitudes down to 0.05% in the 0 rad aluminum bicrystal. In the aluminum bicrystals with the inclination of π⁄36 and π⁄15 rad, the fatigue cracks are nucleated along grain boundaries at the high strain amplitude of 0.13% only, but are not nucleated at the low strain amplitude of 0.05%. The number of cycles to failure of the 0 rad bicrystal is lower than those of the π⁄36 and π⁄15 rad bicrystals, suggesting that the active slip on the planes parallel to the grain boundary enhances the crack initiation along grain boundaries.View full abstractDownload PDF (1160K) -
Atsuko Tsuge, Kaoru Mizuno, Tomohiro Uno, Kohei Tatsumi1995 Volume 59 Issue 11 Pages 1095-1102
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDiffusion across the Al2O3 film in the Au/Al2O3/Al film system (the Al film with 1 μm thickness was vapor-deposited on a SiO2/Si substrate and exposed to the atmosphere to form a natural oxide layer, then the Au film was deposited on it.) at temperatures between 25° and 500° has been studied by using Auger Electron Spectroscopy, X-ray Photoelectron Spectroscopy and electrical resistivity measurement. The temperature where Al is detected on the surface of the Au/Al2O3/Al system is 100°C higher than that on the surface of the regular Au/Al system without the Al2O3 film. The activation energies for the intermetallic layer growth of the Au/Al2O3/Al system and the Au/Al system are 110 and 72 kJ/mol, respectively. The Al2O3 film formed by the exposure in air (ca. 3.2 nm in thickness) acts as a barrier for diffusion in Au/Al. In addition, we observed the SEM image of cross section of the Au/Al2O3/Al system. The Au-Al intermetallic layer is formed in the Al layer in the initial stage of Au/Al2O3/Al diffusion by Au diffusion through the Al2O3 film into the Al layer.
On the other hand, we studied the effect of annealing environment on the diffusion for the Au/Al2O3/Al system by using 18O as tracer for SIMS analysis. The Au-Al intermetallic layer grows in an island formation for the Au/Al2O3/Al system and when annealed in air, the number of islands decreases. Because, during heat treatment in air, the Al2O3 film is formed continuously by supply of O2 to the Al2O3 film through Au film.View full abstractDownload PDF (768K) -
Takeshi Ohgai, Ryuichiro Shimono, Hideyuki Saitoh, Yasunori Hayashi1995 Volume 59 Issue 11 Pages 1103-1107
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe film structure and the soft magnetic properties of Fe-N films prepared by the RF reactive sputtering method at a substrate temperature of 473 K were investigated. It was shown that the substrate heating during film deposition is effective in improving the soft magnetic property of the Fe-N film. As the ratio R(=PN2⁄Ptotal) of the N2 gas pressure to the (Ar+N2) gas pressure in the sputtering gas increased, the film structure of the α-Fe single phase changed to a mixture of α-Fe and γ′-Fe4N. The lowest coercive force (Hc=63.6 A/m) and the highest initial permeability (μ′=1500 at 1 MHz) of the film were obtained under a sputtering condition of R=8%. Under this condition, the film maintained a high magnetic flux density (Bs=21.6 T) which value is the same as that of bulk Fe. The excellent soft magnetic property was obtained when the film was a mixture of fine grains of α-Fe and γ′-Fe4N without any preferential orientation. At R=3∼5%, Bs value of the film exceeded the one of pure Fe, and the maximum value of Bs=2.44 T was obtained. This was attributed to the nitrogen solution to the α-Fe matrix.View full abstractDownload PDF (394K) -
Katsutoshi Yamada, Syouichi Sekiguchi, Toshihiro Hanamura, Tohru Inoue1995 Volume 59 Issue 11 Pages 1108-1117
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe bending strengths, compressive strengths and interfacial properties between the carbon fibers and the aluminium matrix of the carbon fiber reinforced aluminium alloys (CFRM, Vf=70%) with two PAN based high modulus CFs and a PAN based high strength CF, combined with two types matrix of Al-7.8%Mg alloy and Al-7.1%Si-0.36%Mg alloy, have been studied. These six FRMs have been classified into three types according to the level of their interfacial strengths. The two CFRMs with high modulus CFs and a matrix of Al-7.8%Mg alloy having a high bending strength of 1250 MPa and a low compressive strength of 600 MPa show pull-out fibers on the fracture surface of a bending test specimen under SEM observation and microbuckling of fibers after debonding at the interface on the fractured compression test pieces. We tried a new analytical method using AES on the fractured surface of the bending specimen and it was supposed that the interfacial strength is very low. The two CFRMs with high modulus CFs and a matrix of Al-7.1%Si-0.36%Mg alloy having a low bending strength of 600 MPa and a high compressive strength of 850 MPa exhibit a flat fracture surface on the bending test specimen and a mixture of shear mode crack and microbuckling of fibers on the fractured compression test pieces. The interfacial strength is supposed not so low as the previous sample.
The CFRMs with high strength CFs and a matrix of either Al-7.8%Mg alloy or Al-7.1%Si-0.36%Mg alloy, both having a low bending strength of 450 MPa and a very high compressive strength of 1600 MPa, show a flat fracture surface on the bending test specimen and a shear mode fracture of fibers on the fractured compression test pieces under SEM observation. High resolution TEM identified Al4C3 precipitates at a large concentration at the interface. The interfacial strength for these samples is proposed to be very high.View full abstractDownload PDF (1484K) -
Kozo Nakazawa, Atsushi Takei, Kazuo Kasahara, Akira Ishida, Masae Sumi ...1995 Volume 59 Issue 11 Pages 1118-1123
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of Ni-TiC composite film coating formed by reactive ion plating on fretting fatigue behavior in high strength steel was studied. The friction coefficient between a fatigue specimen and the fretting pad decreased by the presence of film coating. The fretting fatigue strength at 107 cycles increased by 25% over that of the uncoated specimen when the specimen was coated even if the pad was not coated, while it remained unchanged when only the pad was coated. The plain fatigue strength decreased by 20% by the coating. It was shown that the plain fatigue strength and the fretting fatigue strength of the steel were not affected by thermal history during the ion plating process. It is probable that the film itself has resistance to fretting fatigue since the increase in fretting fatigue strength by the film coating cannot be readily explained only by the decrease in friction coefficient.View full abstractDownload PDF (667K) -
Kouji Mimura, Michihiro Kasuga, Michio Nanjo, Minoru Isshiki1995 Volume 59 Issue 11 Pages 1124-1129
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSRemoval of metallic and non-metallic impurities from zirconium with nominal purity of 99.8% has been investigated by the electron beam floating zone melting (EBFZM) in a high vacuum.
Metallic impurities such as iron and chromium, being more volatile than zirconium, volatilized preferentially and their contents were reducible to below a few mass ppm after three zone passes at the zoning speed of 2 mm/min. Although no decrease of hafnium, with a slightly lower vapor pressure than zirconium, by volatilization was observed, the redistribution of hafnium, caused by segregation effect, has been found. Deoxidation of zirconium by evaporation of zirconium suboxide like ZrO was scarcely noticed, but it was found that the oxygen content was reduced to below one-half of the initial content in near the final end of the zone melted portion, due to the segregation effect. Segregation of carbon towards the final end was also found, although decarburization by the CO gas evolution was not observed. The effective distribution coefficients for oxygen and carbon at the zoning speed of 2 mm/min were estimated to be 1.5∼2 and 0.7∼0.8, respectively.View full abstractDownload PDF (593K) -
Kazumi Tani, Yoshio Harada, Chang-Jiu Li1995 Volume 59 Issue 11 Pages 1130-1135
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSLamellar structure, splat formation of molten droplets, coating microstructure, transfiguration of carbide particles and deposition yield of the powders in high velocity oxygen-fuel flame spraying of WC-Co coatings using powders with different morphologies were examined. The ratio of the particle diameter to the thickness of splats determined in this experiment is 7 to 17. These values are in good agreement with the calculated values according to the splat formation model proposed by Jones et al.
The formation of coating deposits is followed by the expanding flow of the molten binding phase accompanying solid WC particles. The smaller size of WC particles in the spray powder allows the fluidization and flattening together with the molten binding phase, on the contrary, the flattening behavior of particles are restrained by the size of WC particles in the case that the size of spray powder is large. Susceptivity to flattening of the spray powder tends to result in the compactness or the high density of the coating. Consequently, spray powders composed of the smaller size of WC particles allow the formation of the denser coatings. The selection of the spray powder composed of smaller-sized primary WC particles and the moderately larger size of cermet particles is effective for the higher deposition yield of WC-Co spraying.View full abstractDownload PDF (867K) -
Kazumi Tani, Yoshio Harada, Yasuyuki Takatani1995 Volume 59 Issue 11 Pages 1136-1142
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThermally sprayed cobalt-bonded tungsten carbide coatings have been widely used as various wear resistant materials in dry environment. However, generally they have poor corrosion resistance against aqueous solution. The WC-20 mass%Cr3C2-7 mass%Ni(WC-Cr3C2-Ni) spray material, which is a typical WC cermet with non-cobalt binding phase, is sprayed by means of the high velocity oxygen-fuel flame process. Substantial factors that are controlling the coating properties such as microstructure, electrochemical characteristics and abrasive wear resistance are evaluated compared with WC-12 mass%Co(WC-12Co) sprayed coatings. The diameter of the carbide particle, 2.80 μm, and the length of the mean free path, 4.01 μm, determined for WC-Cr3C2-Ni sprayed coatings are almost comparable to those for WC-12Co coatings, respectively. This results suggest that both coatings are almost equivalent in mechanical properties. The passive current density for sprayed WC-Cr3C2-Ni coating is about ten times less than that for WC-12Co coatings. The corrosion resistance of WC-Cr3C2-Ni sprayed coating in aqueous solution is superior to that of WC-12Co coatings. Microhardness and abrasive wear resistance of sprayed WC-Cr3C2-Ni coatings are comparable to those of WC-12Co sprayed coatings.View full abstractDownload PDF (1123K) -
Shinji Hirai, Hiroshi G. Katayama, Yoichiro Uemura, Mamoru Mitomo1995 Volume 59 Issue 11 Pages 1143-1148
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSExperiments were conducted in order to elucidate the hydration process of AlN at various temperatures between freezing and boiling points of water. At the temperatures below 293 K, the hydration did not occur after even an immersion for long time and an increase of oxygen content in AlN was not also observed. At the temperatures higher than 323 K, the hydration proceeded rapidly. It was confirmed that generated ammonia was immediately dissolved into water, simultaneously partially vaporized as an ammonia gas. At the temperatures higher than 343 K, after the quantity of ammonia in water increased rapidly in the initial stage of reaction, it decreased slowly. On the other hand, the quantity of ammonia continued to increase for a long period of time at 323 K. The quantity of evaporated ammonia increased with the increasing temperature and duration of immersion. An amorphous pseudoboehmite as a hydrate was produced in the initial stage of reaction, after which a crystalline beyerite was produced gradually. The reaction rate in the initial stage increased abruptly with the increase of temperature. However. after the duration of 0.9 ks at the temperature of 323 K and above, the reaction rate was reduced rather at higher temperature. The reason for the reverse of reaction rate were presumed that the progress of reaction was inhibited due to the increase of the degree of supersaturation of ammonia in water with increasing temperature and the covering of AlN particles with a dense beyerite, In addition, the reaction rate decreased drastically with increasing a grain size of AlN.View full abstractDownload PDF (893K) -
Takeo Sumida, Takeshi Ikuno, Nobuo Otsuka, Toshio Saburi1995 Volume 59 Issue 11 Pages 1149-1156
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe SUS321H and SUS347H steel tubes, extensively used as superheaters and reheaters in fossil fuel-fired power plant boilers, were subjected to long term steam oxidation tests for up to 3.6×107 s (10000 h) to clarify the steam oxidation behavior.
It was revealed that the scales formed on the both steel tubes exposed in the steam of 848∼923 K for 1.08×106∼3.6×107 s are composed of an outer scale (Fe3O4) and an inner scale ((Fe, Cr, Ni)3O4), and that their thickness ratio is 45:55. When the boundary between the inner scale and the substrate metal reaches to a grain boundary of the original metal, a Cr-rich oxide layer is formed there. The Cr rich oxide layer protects the metal from oxidation. Thus, the growth of the inner scale does not obey the parabolic oxidation law. The inner scale thickness, di, can be expressed as a function of time, t, by the following equation.
(This article is not displayable. Please see full text pdf.)
\ oindentwhere kE is a function of temperature and α is a function of grain size.View full abstractDownload PDF (1098K) -
Takehiko Itagaki1995 Volume 59 Issue 11 Pages 1157-1164
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFor the fabrication of sintered W-Hf-C alloy, coating of HfC on tungsten powder was attempted by a fluidized bed chemical vapor deposition (CVD). A commercial tungsten powder 3∼5 μm in diameter was used. Argon gas was employed as a fluidized bed former and hafnium chlorides, methane and hydrogen were utilized as raw materials of CVD. Hafnium chlorides were made by internal chlorination. At the preliminary investigation on the formation of fluidized bed, a granular ceramic filter was revealed to have a good performance as a distributor for fine tungsten powder. A foam filter was not suitable for a distributor which was choked in a short operation time. Powder feeding of about 10 g/cm2 associated with argon velocity of 0.2∼0.5 m/s was suitable for forming a stable fluidized bed. W powder showed good fluidity at room temperature due to the existence of WO3 on the particle surface, but at high temperature the fluidity disappeared because the sublimation of the oxide occurred at 1100 K. In order to make stable fluidized bed at high temperature, pre-coating at 900 K and a forced mixing were necessary. Change of bulk density seemed to be useful to evaluate a fluidity of the powder. Auger analysis indicated that Hf containing coated layer of 9 nm was obtained by fluidized bed CVD at 1553 K. EPMA and GDMS showed the coated powder containing 0.35∼0.4 mass% Hf. The relative density of sintered compact which was obtained by sintering of the coated powder at 2573 K for 3.6 ks in vacuum was 92.7%. The sintered specimen contained large amount of W2C and Hf coexisted with W2C.View full abstractDownload PDF (1360K) -
Gang Han, Hidenori Kuroki, Kenji Shinozaki, Yuji Sano1995 Volume 59 Issue 11 Pages 1165-1171
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of uniformity of carbon concentration on the copper growth in liquid phase sintering of a Fe-Cu-C mixture was investigated. Dilatometric curves were recorded for Fe-8 mass%Cu-0∼0.9 mass%C compacts made of mixed elemental powders and Fe-10 mass%Cu-0∼0.9 mass%C compacts made of a coated Fe-Cu powder and graphite during 1130 K-or 1270 K-40 min presintering and 1400 K-40 min sintering processes in hydrogen. Spool models prepared by winding iron and copper wires on a cylindrical Fe-0.76 mass%C alloy were sintered at 1400 K for 8 min in argon and quenched into water in order to simulate the sintering phenomena of Fe-Cu-C compacts.
The copper growth during liquid phase sintering of the Fe-Cu-C mixed powder compacts decreases with the increasing addition of graphite. The growth of the Fe-Cu-C compacts of identical composition has been higher with 1270 K presintering in the temperature range of γ iron, and lower with 1130 K presintering in the range of α iron or without the presintering. The level of the carbon solution into iron has been higher with the γ range presintering, and lower with the α range one or without them. The spool model has shown the solution-reprecipitation phenomena occurring between iron and the Fe-C alloy. These results suggest that the lack of uniformity of carbon concentration causes the solution-reprecipitation phenomena leading to the rearrangement of particles and the shrinkage or the suppressed expansion of compacts.View full abstractDownload PDF (853K) -
Mikio Ito, Kazuhiko Majima, Shigeru Katsuyama, Hiroshi Nagai1995 Volume 59 Issue 11 Pages 1172-1177
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSm2Fe17Nx permanent magnetic powders have been prepared by mechanical grinding (MG) and subsequent heat treatments for crystallization and nitriding. Sm2.5Fe17 and Sm2.3Fe17 alloy powders have been used as a starting material. The oxygen content of the powders crystallized in vacuum is less than that of the powders crystallized in Ar atmosphere: it is less than 9000 ppm for the Sm2.5Fe17 powders. Consequently, the precipitation of α-Fe, which deteriorates the rectangularity of their demagnetization curves, is suppressed.
After MG for 72 ks and crystallization in vacuum the nitrided Sm2.3Fe17 powders close to stoichiometric Sm2Fe17, has also no α-Fe precipitation. The saturation magnetization and remanence are larger than those of the nitrided Sm2.5Fe17 powders.View full abstractDownload PDF (563K) -
Masahiro Fukumoto, Shinichiro Kato, Motoyoshi Ohwatari, Yahui Huang1995 Volume 59 Issue 11 Pages 1178-1184
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effects of both substrate temperature and particle material on the splat behavior of the plasma sprayed powders impinging on the flat SUS304 steel substrate surface were fundamentally investigated.
The results obtained are summarized as follows:
(1) In the splatting of Ni, Cr, Cu and Mo powder on stainless steel substrate, typical splashing at the substrate temperature of 300 K and a drastic fraction change of the splat pattern, from the form with splashing to the one without splashing with the substrate temperature, were observed. On the other hand, those were not recognized in the case of Al and Ti. It seems that splatting strongly depends on the powder material.
(2) From the observation of the bottom surface of the splat and the comparison of the latent heats of the powder materials, initial rapid solidification of the splat just after the impingement seems to be one of the remarkable reasons for the splashing.
(3) It was revealed that the surface tension of the powder material was one of the dominating factors for the splashing from the relation between surface tension and transition temperature of the powder.
(4) The initial solidification rates of the powder impinged were estimated by the simple splat and solidification model, and the incident of the splashing corresponded well to the relation between solidification rate and surface tension of the powder material.
(5) As for the intervals between solidification and flattenning, it seems that both occur simultaneously when the solidification tends to occur easier, while the flattenning occurs preferentially followed by the solidification when the solidification rate is lower.View full abstractDownload PDF (925K) -
Masahiro Inoue, Ken-ichi Komatsu, Kazushige Kudoh, Katsuaki Suganuma1995 Volume 59 Issue 11 Pages 1185-1191
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe chemical compatibility of reinforcements, processing and fracture characteristics of δ-Al2O3 short fiber and β-SiC whisker reinforced FeAl composites with the matrix composition of 40∼50 at%Al were examined. The β-SiC whisker does not react severely with FeAl in the temperature range below 1400 K. The FeAl matrix composites of full density are successfully fabricated by the reactive hot press sintering at 1273∼1373 K. The proportional limit of Fe-40 at%Al matrix increases slightly by the addition of δ-Al2O3 short fibers due to the extremely weak bonding at the matrix/fiber interfaces. Although the β-SiC whisker reinforced Fe-40 at%Al composites exhibits brittle fracture by the whisker addition beyond 15 vol%, the remarkable strengthening is achieved at volume fractions of 5∼10 vol%. The brittle Fe-50 at%Al matrix is hardly strengthened at room temperature by the additions of δ-Al2O3 short fibers and of β-SiC whiskers. The fracture toughness of the FeAl matrix composites reinforced with both the discontinuous fibers is reduced at higher volume fractions.View full abstractDownload PDF (965K) -
Masanori Hosomi, Takashi Maeda1995 Volume 59 Issue 11 Pages 1192-1198
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTiAl(γ), a promising high temperature intermetallic compound, suffers from its low ductility at room temperature, which is, reportedly, partly due to environmental brittlement. In this work, the environmental effect on room temperature elongation was investigated in polycrystalline Ti-48.5 mol%Al and Ti-49.9 mol%Al with four different microstructures (equi-axed, duplex, nearly lamellar and fully lamellar) controlled by thermo-mechanical treatment.
The environmental effect was not recognized in tensile properties. In the equiaxed and duplex structure, the tensile elongation between 4 and 7.5% is nearly equal in vaccum and in air, indicating that the environmental effect is negligible. In the nearly lamellar and fully lamellar structures, the environmental effect cannot be detected because of very little tensile elongation around 1% in both environments. All the specimens after tensile test showed brittle fracture surfaces and no difference was found between the specimens tested in vacuum and in air.View full abstractDownload PDF (1485K) -
Shigemi Mashino, Takao Horiya, Teruo Kishi1995 Volume 59 Issue 11 Pages 1199-1205
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe microfracture mechanism and fracture toughness of a near α Ti-8Al-1Mo-1V alloy was examined by acoustic emission (AE) source location, AE source characterization and fractography. The specimen with acicular α structure had higher fracture tohghness than that with equiaxed α structure. In the acicular α structure, there were many large-amplitude AE signals corresponding to the generation of microcracks before final fracture. AE source characterization indicated that in the case of acicular α structure, many microcracks of 110∼370 μm were nucleated in a mixed mode at the crack tip, and main crack extended by coalescence of these microcracks in a shear mode. Furthermore, the fracture toughness was evaluated quantitatively, using ductile fracture criterion featured by the characteristic distance derived from AE source characterization. Then, it was found that factors affecting the fracture toughness of the Ti-8Al-1Mo-1V alloy were the colony size in acicular α and the primary α grain size in equiaxed α.View full abstractDownload PDF (1120K) -
Masahiro Susa, Kazuhiro Nagata1995 Volume 59 Issue 11 Pages 1206
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (87K)
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