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Volume 44, Issue 8
Displaying 1-18 of 18 articles from this issue
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Etsuji Kimura, Akio Fuwa, Seitaro Fukushima1980 Volume 44 Issue 8 Pages 839-845
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe reaction between chlorine and Australian ilmenite ore particles preoxidized at 1223 K was studied by iso-thermal gravimetry over the temperature range of 1133∼1223 K and the chlorine partial pressure range of 0.1∼101 kPa. The predominant chlorination reaction was found to be:
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\ oindentThe rate of reaction was reasonably expressed by the unreacted-core shrinking model that the product layer, from which the iron contents were removed, was formed out of the reaction boundary. The kinetic analysis using this model for the ore particles shows that the rate controlling step is the surface chemical reaction at the early stages, when the rutile product layers are thin, and then changes later to the gas diffusion step through the product layer. From analysis of the temperature and pressure dependencies of the reaction rate, the plausible elementary reaction steps of chlorine adsorption and chemical reaction are presented and their physico-chemical values are evaluated.View full abstractDownload PDF (639K) -
Kazuyoshi Takezawa, Kenji Adachi, Shin’ichi Sato1980 Volume 44 Issue 8 Pages 846-852
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe mechanism of the reversible shape memory effect (RSM) is studied for small-grained (φ∼1 mm) Cu-Zn-Al alloys by optical and electron microscopy. Optical micrographic examinations show that crossing structures consisting of two β1′ martensite variants which are formed by heating the specimen under constraint contribute remarkably to the appearance of RSM. The habit plane of one martensite (β1′(I)) in the structure is approximately parallel to the basal plane of the other martensite (β1′(II)) and vice-versa. It is confirmed by electron microscopy that the crossed region of two β1′ variants was transformed to an α1′ martensite of fct structure (3R). Furthermore, around this region in the matrix, special bend contours from localized strain fields were often observed. The above facts lead to a conclusion that the crossing structure plays an important role as a source of the internal stress which induces the original β1′ martensites upon cooling. The formation mechanism of the structure is qualitatively discussed on the basis of stress variation during the heating under constraint. A quantitative discussion of the problem in the next paper will follow the present result in succession.View full abstractDownload PDF (1279K) -
Kazuyoshi Takezawa, Shin’ichi Sato1980 Volume 44 Issue 8 Pages 852-857
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn the previous studies on the reversible shape memory effect in Cu-Zn-Al alloy, it has been verified that a planar structure consisting of α1′ and β1′ martensites is constructed after heating the specimen under constraint and also that this composite structure is expected to produce special stress field by which the original β1′ martensite is induced on subsequent cooling.
In the present paper the above mechanism was crystallographically examined by the phenomenological theory of transformation. The shape deformation due to the two-step transformation, β1→β1′→α1′, and the reverse transformation, α1′→β1′, were first formulated assuming a shear deformation on the close-packed planes in the second transformation, β1′→α1′. The numerical calculations of shape deformation using these formulae with the practical lattice parameters indicate that β1′ martensites with a different orientation from the original one can be formed under the influence of the β1′→β1 reverse transformation of the original one. It is also theoretically confirmed that around the retained α1′ martensites, with which the above β1′ martensites construct the composite structure, the stress field having a sense to produce the original β1′ martensite is reasonably formed.View full abstractDownload PDF (450K) -
Kazuo Kameda, Yoshio Yoshida, Senzi Sakairi1980 Volume 44 Issue 8 Pages 858-863
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThermodynamic properties in liquid silver-tin alloys have been determined for NSn=0.27∼0.80, over the temperature range of 636∼983 K, by the following E.M.F. method:
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Activities of tin show both positive and negative deviations from Raoult’s law, and aSn values agree well with the data measured by Chowdhury et al. but differ from those of Laurie et al. and the others. Activities of silver exhibit negative deviations from Raoult’s law over the whole concentration range.
It was observed that the anomalous behaviors in Δ\barHSn and Δ\barSSn at approximately NSn=0.35 are affected by the phase diagram of this system, suggesting that these strongly concentration dependent anomalies are related to the existence of ζ, ε compound clusters in the melt.
It can be clearly seen that the anomalous fluctuations in the values of Δ\barHSn and Δ\barSSn at approximately NSn=0.65∼0.70, and possibly also at NSn=0.55 in the experimental result of Laurie et al. are difficult to rationalize.View full abstractDownload PDF (412K) -
Kiyoshi Yokogawa, Seiji Fukuyama, Kiyokatsu Kudo1980 Volume 44 Issue 8 Pages 864-869
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTensile behavior of carbon steels (SUY, S15C, S35C and S55C) has been investigated in high pressure hydrogen and argon up to 39.3 MPa at room temperature. The results obtained are as follows:
(1) Yield points and ultimate tensile strength are almost independent of the pressure in either hydrogen or argon.
(2) Elongation and reduction of area in hydrogen decrease with increasing the pressure in contrast with those in argon. The elongation and the reduction of area of carbon steels attain constant values at pressures above a critical value which depends on the carbon content. The critical hydrogen pressure and the critical elongation increase with decreasing carbon content. It is found that the critical elongation corresponds to the point of maximum load on the load-elongation curve in argon.
(3) It is proposed that fracture of carbon steel in hydrogen is caused by cracks grown rapidly on the surface. The surface cracks are induced by local necking which forms at the strain corresponding to the point of maximum load.View full abstractDownload PDF (539K) -
Kiyoshi Yokogawa, Seiji Fukuyama, Kiyokatsu Kudo1980 Volume 44 Issue 8 Pages 870-875
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCrystallographic and morphological investigations have been made of fracture surfaces of carbon steels (SUY, S15C, S35C and S55C) under tensile loading in high pressure hydrogen and argon up to 39.3 MPa at room temperature. The results obtained are as follows:
(1) In argon, the fracture surface characteristics is independent of argon pressure. Only the dimple rupture is observed for SUY, S15C and S35C, and a mixed fracture of dimple and cleavage for S55C.
(2) In hydrogen, predominantly observed is quasi-cleavage fracture propagating concentrically from the surface to the center. Dimple rupture is also observed in the low pressure region. Cleavage fracture is observed for SUY, S15C and S35C in the high pressure region and for S55C over the pressure range tested. Intergranular fracture is found especially for S55C at 39.3 MPa hydrogen.
(3) It is inferred that in hydrogen quasi-cleavage fracture essentially results from hydrogen embrittlement at room temperature, but cleavage fracture proceeds with the notch effect caused by surface carcks.View full abstractDownload PDF (821K) -
Tetsuya Ohashi, Hiroshi Hanzawa, Michiya Kishida1980 Volume 44 Issue 8 Pages 876-883
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSElastic incompatibility stresses in the vicinity of a grain boundary plane are analysed, assuming anisotropic bicrystal models of three-dimensional geometry and using the finite element method. Three types of bicrystals, differing from each other in combination of elastic constants, are analysed, eg, (1) bicrystals of shear strain incompatible type, (2) bicrystals of normal strain incompatible type, and (3) “pseudo-identical” bicrystal.
In bicsystals of types (1) and (2), analyses and discussions are made on distribution of elastic incompatibility stress components reffered to specimen coordinates. And, quantitative changes of elastic incompatibility stresses are examined with various aspect ratios of the bicrystal specimen. As a result, the aspect ratios of the bicrystal specimen are shown to be parameters which mainly affect the gradient of stress distribution. Besides, so called coupling term in a stress-strain matrix is shown to have effects on distribution of elastic incompatibility stresses.
In bicrystal of type (3), resolved shear stresses on some slip systems are calculated. Comparison is made between distribution of these resolved shear stresses and slip line pattern which is previously obtained in an experiment by Hook and Hirth. It is shown that slip process strongly depends on elastic stress field in the early stage of deformation. Discussion is made on probable process of slip line formation under interaction of primary and secondary slip systems in conjunction with the inhomogeneous slip stress field.View full abstractDownload PDF (638K) -
Atsushi Kikuchi, Yuko Yusa, Teiriki Tadaki1980 Volume 44 Issue 8 Pages 884-891
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDeoxidation rate of liquid copper by CO2-CO gas mixture was measured under the conditions of higher temperature and lower concentration of oxygen than those in the previous paper.
The mechanism of chemical reaction was discussed using three different models, and each rate equation was presented as the semi-empirical equation.
The steps of mass transfer in the gas phase, chemical reaction at the gas-liquid interface, and mass transfer in the liquid phase were taken into account in formulating an over-all rate equation.
An empirical equation was presented on the liquid-phase mass-transfer coefficient, which was obtained by comparing experimental data with those calculated by the over-all rate equation.
The rate of deoxidation under the experimental conditions in this work as well as in previous one was estimated from the over-all rate equation.
Dimensionless factors were defined to evaluate each resistance of chemical reaction and both mass transfers.View full abstractDownload PDF (538K) -
Keikichi Nakamura, Takehiro Dan1980 Volume 44 Issue 8 Pages 892-898
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to improve hydrogen absorption and desorption rates, an ion-plating method was applied to the plating of Pd and Ni onto Ta and Nb specimens and the optimum conditions were determined. The structure and properties of the ion-plated films for various plating conditions and some problems connected with hydrogen absorption-desorption cycles were also investigated.
The results obtained are summarized as follows:
(1) From the Auger experiment, the surface of Nb as emery polished is covered by equal amounts of oxygen and carbon and a clean surface was obtained by 120 s sputter-etching (2 nm sputter depth).
(2) As for the argon glow-discharge sputter-etching, we have observed critical values for the discharge voltage at which the sputter-yield becomes approximately zero. The values depended strongly on the purity of argon used and were ∼600 V for Nb and ∼400 V for Ta under purified argon (10−6 ppm O2) and ∼1.8 kV for Nb and ∼1.5 kV for Ta under commercial argon (10 ppm O2).
(3) The scanning electron microscopic observation showed that the films have a columnar structure and there are no significant differences among those under different plating conditions (discharge voltage 0.5∼3.8 kV, Ar pressure 1.3∼8.0 Pa and electric power 3∼30 W).
(4) In many cases, exfoliation of the films occurred in the vicinity of the brittle intermediate phases (NbPd3, NbNi3 etc.), which were formed by the heat treatment around 1170 K.
(5) When Pd ion-plated Nb was subjected to the hydrogen absorption-desorption cycles under 573 K, hydrogen induced rupture of the Nb specimen occurred. Even in this case, the Pd film did not exfoliate from the substrate.
(6) The hydrogen absorption rate of Pd ion-plated Nb deteriorated remarkably after the absorption-desorption cycles at 873∼1173 K. In this case, adsorption of carbon and oxygen onto Nb diffused to the surface of the Pd film was observed.View full abstractDownload PDF (680K) -
Osamu Nittono, Hitoshi Iwasaki, Yasumasa Koyama1980 Volume 44 Issue 8 Pages 899-907
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe structural change with increasing tin content and the shape memory effect in indium rich-(0∼20) at% tin alloy crystals have been studied by means of X-ray diffractometry and electron microscopy supplemented by metallographic methods. The alloys containing 0∼11 at% tin are α-phase solid solutions with a f.c. tetragonal structure (c⁄a>1) at room temperature, the axial ratio increasing continuously with tin content. The indium-(11∼15) at% tin alloys are mixtures of α and β phases, the β phase having a f.c. tetragonal structure (c⁄a<1). The alloys containing more than 15 at% tin are β-phase solid solutions. Etched surfaces of these tetragonal alloys do not reveal any banded structure. The indium-(12.9∼15.0) at% tin alloys show a shape memory effect only when quenched to the temperature of liquid nitrogen, although their effect becomes weak and finally disappears after keeping at room temperature for a long time. The structure of quenched alloys (α′ phase) is quite similar to that of the α phase. The quenched alloys show a banded structure due to transformation twinning parallel to {101} planes. The β→α′ phase transformation is of the diffusionless (martensitic) type, and takes place between 330 K at 12.9 at% tin and 150 K at 14.5 at% tin. The hysteresis of transformation temperatures on heating and cooling is considerably large (29∼40 K), depending on the composition. The features of the shape memory behavior are presented and compared with those of indium-thallium and indium-cadmium alloys which show a similar shape memory, effect, and the mechanism of the shape memory effect are also discussed briefly.View full abstractDownload PDF (1041K) -
Yasumasa Koyama, Osamu Nittono1980 Volume 44 Issue 8 Pages 907-914
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe structural change of the fcc\ ightleftarrowsfct transformation in In-20.5 at%Tl-0.5 at%Li and In-20.7 at%Tl-0.7 at%Li ternary alloy single crystals has been studied by means of the X-ray diffraction profile method and X-ray diffraction topography supplemented by optical microscopy. The alloys transform from the fcc phase to the fct phase on cooling. Since the etched surfaces of these tetragonal alloys always show a banded structure parallel to {101} planes, the fcc→fct transformation takes place with a mechanism involving macroscopic shear, as in the analogous In-Tl binary alloys. The measurements of X-ray diffraction curves at various temperatures show that the axial ratio (c⁄a) of the tetragonal structure greatly decreases toward unity near the transformation temperature, and that a metastable two-phase field is defined over a temperature range which is about 15 K both on cooling and heating. Since no evidence for diffusion is obtained, the fcc\ ightleftarrowsfct transformation is of martensitic type. The temperature hysteresis in the transformation (As-Ms) is too small to be appreciated by the diffraction methods. On cooling the fct region grows without distinct crystallographic relation with the surrounding fcc region. On the other hand, on heating the fcc phase nucleates and grows along the twin boundary. Some features of the transformation behavior are presented and compared with those in the In-Tl binary alloy. The effect of adding Li on the transformation is discussed on the basis of both thermodynamics in the martensitic transformation and psuedo-potential approximation. It is shown that the transformation behavior is of second-order like rather in the ternary alloy than in the binary alloy.View full abstractDownload PDF (980K) -
Nobuyoshi Hara, Katsuhisa Sugimoto1980 Volume 44 Issue 8 Pages 915-924
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSModulated reflection spectra of Co have been measured at various potentials in the passivation and transpassivation regions in borate solutions of pH 8.5 and 11.0. The kinds of oxides or oxyhydroxides which constituted passivation and transpassivation films on Co have been identified by comparing the spectra with those of several Co oxides and oxyhydroxides. Changes in the spectra during the cathodic reduction of the films have also been measured in order to elucidate the in-depth profiles of structures of the films.
It was found that the composition and structure of the films changed remarkably with electrode potential and solution pH. In the solution of pH 8.5, the primary and secondary passivation films had the structures of Co(matrix)/Co1−yO and Co(matrix)/Co1−yO/Co3O4, respectively, and the transpassivation film was of Co(matrix)/Co1−yO/Co3O4/CoOOH. Slightly unlike this, in the solution of pH 11.0, the structures of primary and secondary passivation films changed with increasing potential, that is, from Co(matrix)/Co1−yO/α-Co(OH)2 to Co(matrix)/Co1−yO/Co3O4/α-Co(OH)2, and from Co(matrix)/Co1−yO/Co3O4/β-CoOOH to Co(matrix)/Co1−yO/Co3O4/βCoOOH·CoO2, respectively. The mechanism of formation of these films is also discussed.View full abstractDownload PDF (930K) -
Minoru Nemoto, Jun-ichi Echigoya, Hajime Suto1980 Volume 44 Issue 8 Pages 925-932
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDislocation movements during plastic deformation of L12-ordered Ni3(Al, Ti) single crystals at temperatures between 90 and 873 K have been investigated in-situ by high voltage electron microscopy. Either or both of the two slip systems, {111} octahedral slip and {100} cube slip, operated depending upon the testing temperature and the orientation of tensile axis of the specimen. Movements of {111} slip dislocations were quick and jerly. Once screw dislocations ceased to move, they were immobilized instantaneously. Movements of {100} slip dislocations were smooth and viscous showing high friction stress for the cube slip. The present observations have shown that the positive temperature dependence of the yield stress of γ′-Ni3(Al, Ti) can not be attributable to the intersections between {100} and {111} slip dislocations but to the increasing difficulty of the movements of individual screw dislocations in the {111} slip system with increasing temperature.View full abstractDownload PDF (2217K) -
Minoru Nemoto, Takayuki Honda, Jun-ichi Echigoya, Hajime Suto1980 Volume 44 Issue 8 Pages 933-942
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe temperature and orientation dependences of the flow stress of René 80 single crystals have been studied with respect to dislocation structure. Dislocation movements at high temperatures have been observed in-situ in a high voltage electron microscope. It was found that the {100} cube slip which has been frequently observed in γ′ single crystals at high temperatures is difficult in the two phase René 80. When the Schmid factor for the {100} cube slip is large, dislocations move preferentially in the narrow γ region between the γ′ cuboids at temperatures around 870 K. The dislocation density in the γ region increases significantly. The geometrical arrangement of the γ′ cuboids is an important factor in determining the behaviour of dislocations in the nickel base superalloys which contain a high volume fraction of γ′ cuboids. The {111} octahedral slip occurs suddenly and quickly. It is suggested that a strong resistance exists against the movements of screw dislocations on {111} planes of the γ′ phase also in the two-phase alloy.View full abstractDownload PDF (2431K) -
Kenzo Hanawa, Kiyoaki Akechi, Zenshiro Hara, Takeo Nakagawa1980 Volume 44 Issue 8 Pages 943-948
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSRecently sintered products from cast iron swarf powder have promised superior strength to parent cast iron. This strengthening mechanism has been studied using Fe-Si-C mixed powders with reference to the effects of C content, density and graphite morphology on tensile strength. Reduced iron, atomized ferrosilicon (17%Si) and graphite powders were blended to contain 2.5%Si and various C contents in the range of 0∼2.6%, and compacted at 600 MPa. The preforms were sintered or powder-forged at 1423 K in dry H2 atmosphere for various times up to 43.2 ks, followed by air cool (1 K/s).
The products containing about 1%C, sintered for a long time or powder-forged, showed high strength (900∼1200 MPa), since graphite was spheroidized. But, it is not the case for the products containing more than 2%C. In the formers, sintering proceeds in the state of all C dissolved in γ-phase, therefore, during the long time sintering, pores between powder particles are spheroidized. Powder-forging accelerates this spheroidization. In the latters, however, all C cannot be dissolved in γ-phase, consequently, graphite remains along powder particles’ boundaries. In any case, during cooling, the supersaturating C precipitates as graphite to pores (from pore/γ-phase interface to center) or to the residual graphite. This suggests that the precipitated graphite morphology is determined by the pore or residual graphite morphology.View full abstractDownload PDF (1112K) -
Mitsuo Asawa1980 Volume 44 Issue 8 Pages 949-954
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of both strain-induced α′ martensite in Type 304 steel and NaBr concentration in a solution of 2 kmol/m3 H2SO4 at 368 K on stress corrosion characteristics, was examined. The results show that the α′ and NaBr concentration were major variables affecting the susceptibility to cracking. As the amount of α′ was increased or the NaBr concentration was reduced, the crack density increased and the time-to-fracture decreased gradually and either further increase in α′ or further decrease in NaBr concentration led to general corrosion. The attack tended to proceed along the stress-induced α′ martensite, which was anodically more active than the γ phase in the test solutions. Discussion covered the problem concerning the correlation between susceptibility to stress corrosion and the inhibiting action of bromide ions on the basis of the results of anodic polarization and weight loss measurements, and of the results of the above stress corrosion tests.View full abstractDownload PDF (1629K) -
Mitsuo Asawa1980 Volume 44 Issue 8 Pages 955-959
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSStress corrosion behaviors of Type 304 stainless steel wire in 2 kmol/m3 H2SO4-NaI at 368 K were examined under an initial stress of 324 MPa as functions of the amount of α′ martensite induced by prestraining at various temperatures and NaI concentration. The attack like cracks was observed in the steel with a little α′, particularly in the steel prestrained at 293 K and tested in a solution containing 5×10−2 mol/m3 NaI. The attack, however, was blunt and tended to develop into trenches and/or hollows for the steel with a large amount of α′ in the solution with 5×10−2 mol/m3 NaI, or with a little α′ with NaI concentrations below 10−2 mol/m3. This may be due mainly to the fact that both α′ martensite and γ phase are dissolved in the above conditions. From the observation of stress corrosion morphologies and the change in weight loss with time, it has been found that correlation exists between susceptibility to stress corrosion and chemical stability of the protective layer on the steel.View full abstractDownload PDF (1192K) -
Tomoaki Sakurai, Mikihiko Ito, Kimiyoshi Goto1980 Volume 44 Issue 8 Pages 960-961
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (269K)
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