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Volume 42, Issue 9
Displaying 1-17 of 17 articles from this issue
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Kozo Kitada, Tatuo Tanaka, Fumiyoshi Miyashita, Giroku Miyatani, Toshi ...1978 Volume 42 Issue 9 Pages 823-830
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to make clear the formation process of Cr3C2 from a mixture of chromium oxide and solid carbon, the carburization reaction of chromium oxide to Cr3C2 was carried out at temperatures ranging from 1100 to 1500°C in hydrogen stream (500 ml/min).
\ oindentThe cross-sections and surfaces of partially carburized pellets were observed by a scanning electron microscope.
The results were summarized as follows:
(1) The carburization products were Cr3C2, Cr7C3 and Cr23C6. Cr3C2 and Cr7C3 consisted of a single phase were obtained.
(2) At the reaction temperature of 1100°C, the yield of Cr3C2 reached 93%.
(3) The formed chromium carbides resembled in shape, but they were identified to be Cr3C2, Cr7C3 and Cr23C6.
(4) The formed chromium carbides were polycrystalline. The crystal grain in each phase grew up with an increase of the carburization temperature.
(5) The formation reaction of chromium carbides was markedly affected by the pressure of CO gas.View full abstractDownload PDF (922K) -
Kotaro Kuroda, Yoshitsugu Tomokiyo, Tetsuo Eguchi1978 Volume 42 Issue 9 Pages 831-837
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe critical voltages, Vc, for 222 and 400 reflections from pure Cu and Al and Cu-based alloys with 15 at%Al, and 5 or 15 at%Au were measured by JEM-1000 HVEM to investigate the effect of alloying on the critical voltage effect. The addition of 15 at%Al to Cu causes Vc for the 222 and 400 reflections to increase by 15 and 32 kV, respectively. The addition of 5 at%Au results in decreases of Vc for the 222 and 400 reflections by about 44 and 77 kV, respectively. A decrease as much as 176 kV occurs for the 400 reflection by the addition of 15 at%Au. These results agree with the expectation that the addition of an element with a smaller (or larger) scattering factor than that of the matrix will produce an increase (or decrease) of Vc. The measured Vc was analyzed by the many beam dynamical theory by taking into account systematic 10 beams. From the measured Vc of Cu-Al and Cu-Au alloys, we estimated the B factors and the Debye temperatures by using the corrected scattering factors. In the case of Cu-Al alloy, a fairly good agreement is obtained between the result of the present work and the one obtained by X-ray measurement. The effect of temperature on Vc has also been investigated by using a liquid nitrogen cold stage. The Vc increases with a decrease in temperature, and the temperature dependence of Vc is more pronounced in Cu-Al alloy than in Cu-Au alloy. In order to investigate the effect of short range order on Vc, the differrence in Vc in Cu-15 at%Au alloy between the specimens furnace-cooled and quenched from 400°C has been measured and the change of 5 kV for the 400 reflection has been obtained.View full abstractDownload PDF (615K) -
Koji Tanoue1978 Volume 42 Issue 9 Pages 837-844
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSStress relaxation tests were carried out to study the existence of the mechanical equation of state, σ=σ(y,\dotε) with “Hardness” (y) proposed by Hart and its temperature dependence in polycrystalline molybdenum. Prior to stress relaxation tests, various deformation histories were given by four loading modes of (A) monotonic loading, (B) cyclic loading, (C) strain rate cycling and (D) swaging, respectively, at 292 K. Consequently, any type of deformation history from (A) to (D) shows a good linear relationship with stress-strain rate scaling at the same temperature and forms one concave-upward master hardness curve. The stress-strain rate scaling parameter, m[=(dln\dotε⁄dlnσ)ν], is different from each other by the deformation history. It is therefore concluded that the mechanical equation of state, σ=σ(y,\dotε) lacks generality, because the form of the relationship changes when the deformation history differs. While the scaling relations of the hardness curves following monotonic loading hold good over the temperature range from 292 to 550 K, m decreases drastically and the master hardness curve shows a less concave-upward behavior with increasing temperature.View full abstractDownload PDF (647K) -
Hiroyasu Araki, Yoshinori Fujimura, Kenzaburo Kumada1978 Volume 42 Issue 9 Pages 844-850
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to investigate the σ phase formation in a series of 25 Cr-20 Ni steels, the effect of prestrain up to 20% by tension on the σ phase formation at 800°C was studied for low carbon 25 Cr-20 Ni steel with and without an approximately 3% addition of Mo or Si.
The results obtained are as follows:
(1) The effect of prestrain on the σ phase formation was observed in all of the three specimens and the σ phase was formed in the early stages of heating in the prestrained specimens.
(2) The morphology of the σ phase thus formed was not the widmanstätten type, but the σ phase existed along the annealing twin boundaries and its amount, slightly increased with increasing prestrain.
(3) In the strongly prestrained specimens, the σ phase formation also occurred on the slip bands in the vicinity of grain boundaries.
(4) In the undeformed specimens with Si and Mo, there were denuded zones where the σ phase formation was hardly observable.
(5) It seems probable that the σ phase formation in the prestrained specimen is enhanced by the deformation-induced crystal defects, while that in the undeformed specimens depends on the point defect concentration.View full abstractDownload PDF (2169K) -
Hidehiko Kamide, Hideo Sugawara1978 Volume 42 Issue 9 Pages 850-857
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe role of hydrogen in the mechanism of stress corrosion cracking of 18-8 stainless steel has been studied under cyclic charging of the cathode and the anode in H2SO4-NaCl solution.
Under the cathodic charging without applied stress, the formation of ε- and α′-martensites in the austenite grain were confirmed by X-ray diffraction and transmission electron microscopy. These martensites were dissolved during anodic charging. The repetition of cathodic and anodic charging resulted in the formation of the corrosion striation.
On applying a stress of 70% of the yield stress, deep cracks were formed during cyclic charging, but no cracks were observed under the cathodic charging.
It is concluded that the occlusion of hydrogen will facilitate the formation of martensite, thus stress corrosion cracking be enhanced with the repetition of the formation and dissolution of martensite by cathodic and anodic charging.View full abstractDownload PDF (1067K) -
Nobuya Iwamoto, Norimasa Umesaki1978 Volume 42 Issue 9 Pages 857-863
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to clarify the structural change in GeO2 glass due to the addition of alkali metal oxides, the radial distribution functions for Na2O-GeO2 glasses containing 0, 10, 20 mol%Na2O were determined by X-ray diffraction measurement.
The results are summarized as follows:
(1) The structure of GeO2 glass was composed of tetrahedral GeO4 basic structural units with an average Ge-O distance of 1.74×10−10 m. The average structure of GeO2 glass in the short range resembled that of the quartz modification.
(2) Analysis of the radial distribution functions indicated that oxygen coordinations around some of Ge4+ ions in Na2O-GeO2 glasses changed from GeO4 tetrahedra to GeO6 octahedra when Na2O was added up to 20 mol%.View full abstractDownload PDF (523K) -
Shigeo Tsujikawa, Yoshihiro Hisamatsu1978 Volume 42 Issue 9 Pages 863-870
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSRotating-bending fatigue test of Type 304 steel rods has been conducted potentiostatically in 1 N H2SO4 containing 0.5 M NaCl at 25°C. From the experimental results reported previously, it was concluded that cracks developed from the dissolving walls of corrosion-pits in the presence of pronounced faceting dissolution. Then the individual contributions from crystallographic pits and the corrosion-pit as a mechanical notch were studied separately by using the following technique. The rod subjected to solution heat-treatment was first pitted potentiostatically in the same solution and washed with running water to repassivate the corrosion-pits and remove the covers of the pits. The passivated specimen was then electrochemically etch-pitted in the active potential region, followed by rotating-bending at the same potential. Initiation sites for micro-cracks were the edges of growing etch-pits developed in the inner surfaces of the passivated corrosion-pits. The observed orientation relation between micro-cracks and etch-pits showed the fact that cracks penerated along {100} planes. The critical size of the etch-pits which could form micro-cracks was independent of the depth of the passivated corrosion-pits. The development of micro-cracks into macro-cracks that would lead specimens to failure occurred only at the bottoms of the passivated corrosion-pits of which depth was larger than a threshold value. In contrast with the situation in the micro-crack initiation, the crack growth rates depended significantly on the depth of the passivated corrosion-pits and those at the threshold depth were found to be just above the faceting dissolution rate. The presence of the threshold depth of the passivated corrosion-pit as a mechanical notch is interpreted as meaning that the rate of crack growth must be higher than that of the faceting dissolution.View full abstractDownload PDF (647K) -
Kuniaki Ushijima, K\={o}ichi Fujii1978 Volume 42 Issue 9 Pages 871-875
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA process for production of fine WC powders using Co3O4 as an additive was investigated. The mixed powder of WO3, carbon black and 0.4 to 6.25%Co3O4 was reduced and carburized in H2 at various temperatures. This report deals with the result of the examination on the operating conditions and the particle size of the obtained WC.
From the chemical analysis of combined carbon contents of the products and identification of the compounds by X-ray analysis, it was found that the mixed powder containing more than 1.6%Co3O4 could be carburized at 900°C. When the Co3O4 content is less than 1.6%, the lower the Co3O4 content the higher the carburization temprature, and the effect of Co addition was almost negligible at less than 0.4%Co3O4. The WC particle size obtained became coarser as the degree of reduction, carburization temperature and Co3O4 content increased. The particle size of more than about 0.6 μm could be controlled by regulating these three factors. Although in this process the WC was carburized at a much lower temperature than in the usual process, where WC was prepared by the reaction between W and C, its grain size of WC determined by X-ray diffraction was comparatively large and became larger with increasing Co3O4 content of the mixed powder.View full abstractDownload PDF (571K) -
Kuniaki Ushijima, K\={o}ichi Fujii, Takeo Ohtsuka1978 Volume 42 Issue 9 Pages 876-881
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe processes for the formation of WC and Co mixtures from a mixed powder of WO3, Co3O4 and carbon by heating in H2 atmospher were investigated by means of differential thermal analysis and identification of the compounds by X-ray analysis.
In the usual formation process of WC from the mixture of W and C, W2C was formed at about 980°C and the reaction between W2C and C occurred above about 980°C, but WC formation was incomplete even at 1150°C. However, WC was formed completely at about 900°C when Co took part in the reaction between W and C, as WC was produced from eta carbides of W, Co and C. The reduction of Co3O4 and WO3 by H2 occurred at a lower temperature and Co6W6C was formed above about 740°C. An abrupt exothermic reaction occurred at about 840°C and terminated at about 900°C. In this temperature range there occurred the reactions to form Co3W3C from Co6W6C and further to form WC and Co from Co3W3C. At the same time, W2C was also formed from W and C, which immediately reacted with Co and changed to Co6W6C and WC. The carburization of eta carbides and the reaction between W2C and Co simultaneously occurred from about 840°C and the perfect mixed powder of WC and Co was produced at 900°C.View full abstractDownload PDF (488K) -
Hiroh Numata, Shiro Haruyama1978 Volume 42 Issue 9 Pages 882-886
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSElectrochemical study of nickel has been made in LiCl-KCl eutectic melt containing nitrate, with regard to the electrochemical estimation of the corrosion rate.
The experiments were made under argon atmosphere at 500°C. In the absence of nitrate ion, the anodic polarization of nickel yielded a well defined Tafel line with a slope of 90 mV/decade. In the presence of nitrate ion, the cathodic polarization curves exhibited a limiting current, which was proportional to the concentration of nitrate. The limiting current was attributed to the diffusion controlled reduction of nitrate ion. With increasing concentration of nitrate, the corrosion potential shifted to the noble direction by 67 mV/decade of mol%, and the corrosion rate increased.
The behaviour was fully explained by the superposition of the anodic dissolusion of nickel and the diffusion limited reduction of nitrate, based on the mixed potential theory. Therefore, the corrosion rate was found to be controlled by the diffusion of nitrate. It was also found that the corrosion rate estimated by the polarization resistance methode was consistent with that estimated from the weight loss.View full abstractDownload PDF (370K) -
Genjiro Mima, Fukuji Inoko, Ken Atagi1978 Volume 42 Issue 9 Pages 887-893
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAluminum bicrystals with longitudinal crystal boundaries with twist angles of about 22° (0.38 rad) and {111} planes were produced by a modified Bridgman method. They were tested by the bending fatigue testing machine under constant strain amplitude and the rate of cycles 30.4 Hz.
It was found that fatigue cracks initiated along the crystal boundaries. The initiation of the fatigue cracks along the crystal boundaries was due to the operation of secondary slip systems whose slip planes were parallel to the crystal boundary one.View full abstractDownload PDF (672K) -
Hisashi Suzuki, Koji Hayashi, Yasuro Taniguchi1978 Volume 42 Issue 9 Pages 894-898
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe transverse-rupture strength of WC-(10∼30)%Co alloys was studied at temperatures mainly from 600 to 1000°C in relation to their domain size of the binder phase. Because it was found in the previous studies by the authors that structural defects tended to locate on the domain boundary with their size variations according to the domain size, and moreover fracture occurred frequently from the domain boundary. Two sorts of specimens with coarse and fine domain sizes were made in each alloy system by controlling the cooling rate after sintering.
The results obtained were as follows: (1) At temperatures above about 600°C, the strength of each alloy system was always higher in the specimen with coarse domain size, being in contrast to the case at lower temperatures. (2) The effect of domain size at high temperatures was explained from the fact that the growth of stable crack as a fracture source was highly checked in specimens with coarse domain size, because, in these specimens, a stable crack which started from a domain boundary didn’t easily propagate along the boundary.View full abstractDownload PDF (557K) -
Hidehiro Onodera, Hiromu Oka, Imao Tamura1978 Volume 42 Issue 9 Pages 898-905
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn an Fe-25%Ni-0.65%C austenite, both deformation twinning and martensitic transformation can be induced during deformation. In the present investigation, the effect of deformation twinning on the deformation-induced martensitic transformation was examined to reveal the effect of applied stress and plastic strain on the deformation-induced martensitic transformation.
The results obtained are as follows.
(1) In the temperature range between Ms and Msσ, the critical stress for martensite formation increased linearly with increase in temperature, and the morphology of martensite was the same as the one thermally transformed.
(2) In the temperature range above Msσ, the critical stress for martensite formation was considerably lower than that expected by extrapolating the stress-temperature line between Ms and Msσ. The martensite was frequently observed at the intersection of two deformation twins and the grain boundary or the annealing twin boundary on which deformation twins impinged.
(3) Such martensite was considered to be formed by the aid of both the concentrated stress due to the impingement of deformation twins and applied stress.
(4) Martensite which observed at the junction of two deformation twins was considered not to be formed from the embryo produced by the intersection of two shear bands which suggested by Olson and Cohen. From the analysis, the combination of these deformation twins did not correspond to Bogers-Burgers’s double shear.View full abstractDownload PDF (847K) -
Yuzuru Sato, Tatsuhiko Ejima1978 Volume 42 Issue 9 Pages 905-912
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPhase diagrams of LiCl-AlCl3 and NaCl-AlCl3 binary systems have been determined over the composition range of 0∼100 mol%AlCl3 by means of the direct observation, DTA method and X-ray analysis. The results obtained are summarized as follows:
(1) The chemical compounds LiAlCl4 and NaAlCl4, were recognized at the composition of 50 mol%AlCl3, and their melting points were 416 and 427 K, respectively.
(2) The two-liquid regions were observed in the composition range more than 82 mol%AlCl3 for the LiCl-AlCl3 system, and in the composition range more than 79 mol%AlCl3 for the NaCl-AlCl3 system.
(3) The eutectic points were detected at the composition of 57 mol%AlCl3 and the temperature of 383 K for the LiCl-AlCl3 system, and at the composition of 60.5 mol%AlCl3 and the temperature of 381 K for the NaCl-AlCl3 system.
(4) In the composition range less than 50 mol%AlCl3, the liquidus lines of each system show the high temperature as long as the content of AlCl3 increares from 0 to 40 mol% and then rapidly decrease with the increase of AlCl3 to the melting points of the chemical compounds. The tendency to maintain the high temperature is remarkable for the LiCl-AlCl3 system.
(5) The chemical compounds LiAlCl4 and NaAlCl4 are known to be very stable. Therefore, the activities of the components were calculated from the phase diagrams by assuming the quasi-binary systems LiCl-LiAlCl4 and NaCl-NaAlCl4 in the composition range of 0∼50 mol%AlCl3. The activities show large positive deviations from Raoult’s law, and the smaller the cationic radius, the larger becomes the deviation.View full abstractDownload PDF (677K) -
Isamu Tanaka, Takashi Otsuki, Kimitaka Sato1978 Volume 42 Issue 9 Pages 912-915
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt is frequently necessary to try a macroscopic in-depth analysis in the μm range for the surface layer of metallurgical materials. Such a surface layer analysis is difficult when using secondary ion mass spectrometry (SIMS) or Auger electron spectrometry (AES) as up-to-date surface analysis technique, because long sputtering times are needed for etching. In the present study, the usage of spark source emission spectrochemical analysis was investigated, and as the result, it was made clear that the in-depth analysis of about 12 μm units was possible by a proper choice of the polishing and measurement conditions. This method was applied to the clarification of the origin of errors in the emission spectrochemical analysis of steel specimens after rolling and heat treatment and to the material tests of pipes for heat exchanger, and was then confirmed to be a useful technique for the surface analysis of materials.View full abstractDownload PDF (407K) -
Kunio Shiobara1978 Volume 42 Issue 9 Pages 916-922
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSChemical pitting corrosion tests in neutral 1.0 M NaCl solution containing 0.5 M K3Fe(CN)6 and measurements of pitting potentials Vc′ and Vcre′ for stainless steel open surface and creviced specimens in 0.5 M NaCl solution were conducted to study the resistance to pitting and crevice corrosion of 18 Cr-14 Ni stainless steels to which the alloying elements Mo, Si and N had been added. The following results were obtained. (1) Mo and N increased the resistance to both pitting and crevice corrosion, whereas Si increased only the pitting resistance and had no effect on the crevice corrosion tendency. The beneficial effects of Si and N were found to be pronounced especially when 1∼3%Mo had been alloyed together with them. (2) In many cases, the pitting potentials of creviced specimens Vcre′ were found to be 0.3∼0.4 V more negative than those of open surface specimens. However, in the case of 18 Cr-14 Ni-3.5 Si-0.2 N stainless steel, Vcre′ was about 0.9 V more negative than Vc′, indicating a greater susceptibility to crevice corrosion. For practical purposes of assessing the susceptibility and/or resistance of an alloy to localized corrosion, it is essential that the pitting potential Vcre′ of the creviced specimen as well as that of the open surface, Vc′, be measured.View full abstractDownload PDF (628K) -
Takayoshi Yoshimori, Minako Shiga1978 Volume 42 Issue 9 Pages 923-924
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (120K)
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