All issues
Volume 42, Issue 2
Displaying 1-17 of 17 articles from this issue
- |<
- <
- 1
- >
- >|
-
Atsumi Ohno, Tetsuichi Motegi, Kenji Ishibashi1978 Volume 42 Issue 2 Pages 107-113
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTo know the origin of equiaxed eutectic grains of eutectic alloys, the macrostructures and microstructures of ingots, solidified under static and vibration conditions, of the zinc-aluminum, aluminum-copper, aluminum-nickel, lead-tin, and tin-zinc systems were examined.
In alloys consisting partly of the eutectic, regardless of being a hypoeutectic or hypereutectic alloy, primary crystals separated from the mold wall in the initial stage of solidification and showed the tendency to appear in the central region of the ingots. When primary crystals were not of the leading phase in an alloy, the eutectic which formed on the mold wall grew in to columnar grains independently of the existing primary crystals in the liquid, while when the primary crystals were of the leading phase, the formation of equiaxed eutectic grains occurred on the primary crystals in the liquid.
It was also found that eutectic grains on the mold wall could be separated by turbulence in the liquid.View full abstractDownload PDF (961K) -
Junji Kihara, Fumitaka Iori, Yasunori Torisaka, Isao Gokyu1978 Volume 42 Issue 2 Pages 114-118
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn the production process of concrete piles and concrete poles, prestressed concrete steel wires are held at 363 K for 7.2 ks and at 453 K for 18 ks after being embedded in concrete to increase their strength. In this process it is necessary to decrease the stress relaxation of the prestressed concrete steel wire. Therefore, strain-tempering loaded in the blueing process hase been investigated.
The authors examined strain-tempering conditions and mechanical properties of the prestressed concrete steel wire, and discussed the strain-tempering mechanism.
In strain-tempering, the load must be removed at room temperature for the decrement of stress relaxation. As the result, strain-tempered materials have large σE, and recovery of strain except that elastic strain occurs upon unloading at 473 K, but only elastic strain occurs at room temperature. Therefore, it seems that the strain aging by free C and N is not the main factor in the improvement of relaxation behaviour in strain-tempering.View full abstractDownload PDF (371K) -
Kunihiro Hisatsune1978 Volume 42 Issue 2 Pages 118-124
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe ordering processes of equiatomic alloy CuPt by anisothermal annealing were investigated by means of electrical resistivity measurements, X-ray diffraction and optical microscopic observation.
The main results are as follows:
(1) Disordered CuPt attains an equilibrium ordered state via the coexistence state of disordered and ordered phases.
(2) There are three stages on the ordering process in CuPt alloy; the first stage corresponds to the migration and annihilation of quenched-in excess vacancies (stage Ia), the second to the annihilation of secondary lattice defects (Ib) and the third to the diffusion of equilibrium vacancies (II).
(3) Discontinuous ordering corresponding to the boundary reaction occurs at stage Ia followed by continuous ordering to perfect order at stages Ib and II.
(4) The activation energies for stages Ia, Ib and II are 0.77, 1.05, 2.42×105 J/mol, respectively.View full abstractDownload PDF (791K) -
Hideki Hagi, Yasunori Hayashi, Namio Ohtani1978 Volume 42 Issue 2 Pages 124-130
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSRecently much interest has been focused on the role of hydrogen-dislocation interactions in relation to the susceptibility of materials to hydrogen embrittlement. By using electrolytic iron as a specimen, tensile tests were carried out under conditions of concurrent cathodic polarization to maintain a concentration of dissolved hydrogen in a dynamic steady state. Since cathodic hydrogen charging causes internal damage and dynamic interactions of dissolved hydrogen with moving dislocations, tensile stress shows various changes with charging conditions. In the present study the influence of the dissolved hydrogen on the flow stress was distinguished from that of the hydrogen damage by selection of the charging and tensile conditions. While the dissolved hydrogen increases flow stress by a dynamic interaction with moving dislocations, the precipitation of hydrogen produces a number of cracks and deformation, and decreases flow stress.
The gas pressure produced by hydrogen damage, such as cracks or voids, was estimated by using the apparent hydrogen solubility deduced from a trapping model and the equation proposed by de Kazinczy. The gas pressure thus estimated was comparable to the tensile strength of the iron specimen. The relation between the applied stress and the internal stress resulting from hydrogen precipitation was also studied by measuring the stress changes caused by heavy hydrogen charging during stress relaxation. The stress relaxation caused by the heavy hydrogen charging was mainly due to the high stress caused by the precipitation of hydrogen.View full abstractDownload PDF (705K) -
Kazuo Masato1978 Volume 42 Issue 2 Pages 131-136
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSChemical vapour deposition of silicon carbide onto carbon fibres has been carried out at temperatures between 1050 and 1400°C using trichloromethylsilane vapour carried with hydrogen. A carbon fibre tow used as a substrate was heated by the direct passage of an electric current. The flow rates of hydrogen gas were 70, 140 and 210 cm3/min. The temperature of trichloro-methylsilane vapour was 24±4°C. The total pressure of reaction gases was 1 atm. At the hydrogen flow rates of 70 cm3/min and 140 cm3/min, silicon carbide was deposited throughout the bulk tow, but the deposit obtained at the outer part of the tow was thinner than at the central part. The thickness of the deposit layer calculated as cylindrical surface deposition increased linearly with the deposition time, rapidly up to about 1 min and thereafter slowly. X-ray analysis revealed that the deposit was predominantly β-SiC. The activation energy for the deposition of silicon carbide was 61 kJ/mol, except when the deposition time was very short. The relation between the surface morphology of deposited silicon carbide and the coating conditions was investigated and three types of deposition were found.View full abstractDownload PDF (624K) -
Hideto Koga, Yasuo Uchiyama, Takafusa Aki1978 Volume 42 Issue 2 Pages 136-142
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTo study the interdiffusion between solid iron and liquid zinc, high purity iron test pieces were dipped into high purity zinc baths of 440∼600°C. The thickness and the growth rate of alloy layers on the iron surface, and the quantity of iron reacted with zinc (iron weight loss, Fe (total), iron remained in the alloy layers, Fe (alloy), and iron dissolved into the zinc baths, Fe (zinc)) were measured.
A Γ layer was formed next to the iron, followed by a δ1K layer. Up to 490°C, a δ1P layer and a ζ layer were formed next to the δ1K layer. The ζ layer decreased with immersion time, and disappeared at 490°C. The growth rate of the δ1 layer was higher than that of the ζ layer. Over the temperature range between 500 and 560°C, a (δ1+η) mixture layer was formed next to the δ1 layer, and dropped off into the bath. Above 560°C, the δ1K layer formed on the surface of the alloy layers dropped off into the bath. Its thickness remained constant (about 10 μm). The total thickness of the alloy layers had a peak at about 520°C.
Fe (total) corresponded to the sum of Fe (alloy) and Fe (zinc), and had a peak at 520°C for a short immersion time (t≤20 min), at 500°C for a long immersion time (t≥50 min); the values of Fe (total) were higher than those in other experiments above 540°C. Fe (alloy) had a peak at about 520°C, corresponding to the thickness of the alloy layers; its peak values remained constant (t≥20 min). Fe (zinc) had a peak at 500°C for a long immersion time (t≥50 min).View full abstractDownload PDF (991K) -
Genjir\={o} Mima, Katsutaka Nakamura1978 Volume 42 Issue 2 Pages 143-148
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe degree of reduction in whisker length and whisker-surface damage is higher in metallic materials than in plastic materials. Then the special methods have been devised for making whisker reinforced metallic composite materials. Among those methods, there is the fluid mechanical alignment of whiskers developed by Calow and Wakelin.
The purpose of our work is to resolve the problems of Calow and Wakelin’s method and then to obtain the optimum processing condition. This report presents the experimental results on the effects of aspect ratio of the rectangular duct cross-section on the discontinuous fiber orientation in high viscous liquid flow when the ratio of the discontinuous fiber length to the duct depth (the minor width) was comparatively large. Here the aspect ratio of the duct cross-section is defined as the width to depth ratio.
As a result, it can be said that the discontinuous fibers in the duct become disarranged in the flow direction with increasing aspect ratio of the duct cross-section.View full abstractDownload PDF (537K) -
Kenji Morii, Mitsuo Mera, Yutaka Nakayama1978 Volume 42 Issue 2 Pages 148-155
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe deformation behavior of (211) [\bar111] single crystals of 70/30 brass during rolling has been examined metallographically from a view point of the deformation mode which is characterized by the development of shear bands.
It is shown that a shear band is nearly perpendicular to the side surfaces of the specimen and inclined at 25∼35 deg to the (111) twinning plane. At larger reductions than 40%, at which extensive mechanical twins were nucleated, peculiar slip traces deviated from the (111) plane appear among the slip trace groups of the slip systems having the slip plane parallel to the twinning plane. It is shown that the areas where these peculiar slip traces exist have higher density of mechanical twins and are accompanied by a local lattice rotation of ∼30 deg about the [01\bar1] transverse direction of the specimen. With increasing rolling reductions, these areas are closely arranged so as to form the band-like regions. It is concluded that linear arrangement and accumulation of the peculiar slip traces in these regions cause the formation and development of shear bands.View full abstractDownload PDF (1659K) -
Setsuo Furihata, Kazuo Akashi, Jen-chi Huang, Shun-ichi Kurosawa1978 Volume 42 Issue 2 Pages 155-162
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA modified method for purification of the fused LiCl-KCl eutectic mixture and the unfavorable effect of various impurity ions such as Ag+, Sb3+, Pb2+, Fe2+, Cr3+, Zn2+, Mg2+ and OH− contained in the fused salt were investigated. A very small amount of chloride or hydroxide was added to the LiCl-KCl melt purified, and then the reduction wave in the polarography of the impurity ions was recorded by using a Pt micro-electrode and a Pt/Pt2+ reference electrode at 673∼723 K.
The bubbling of dry HCl and Ar and filtration through a pyrex or silica glass filter were very effective for the purification of the fused LiCl-KCl mixture. After the filtration, the residual current decreased to a value less than 5 μA at a −2.0 V potential indicated by a Pt micro-electrode (0.8 mmφ) vs reference electrode Pt/Pt2+ 9 mol/m3. This value shows that the LiCl-KCl eutectic mixture is purified sufficiently for successive experiments.
The half wave potential of Ag+ was −0.8∼−0.9 V and the impurities having a low boiling point such as SbCl3, which increased the residual current level, could be easily removed by only Ar bubbling. Other cations causing the increase of residual current over the range of −1.0∼−2.0 V were Pb2+, Fe2+, Zn2+ and Cr3+. The remarkable increase of residual current at more negative potentials than −2.0 V which may be due to the reduction wave of OH− and Mg2+ could be observed.
The adsorption of moisture into the fused salt from air increased the OH− content and the residual current level. Accordingly it is very important to perform careful dehydration of the fused salt used as a solvent melt for correct electrochemical measurements.View full abstractDownload PDF (631K) -
Nobuya Shinozaki, Kazuichi Mizoguchi, Yukio Suginohara1978 Volume 42 Issue 2 Pages 162-168
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSElectrical conductivity measurements and electrolytic analysis of MnO-SiO2-TiO2 melts have been carried out in order to clarify the behavior of TiO2 and MnO in silicate melts.
Previous studies on the electrical conductivity of Na2O-SiO2-TiO2 and CaO-SiO2-TiO2 melts have indicated that six oxygen coordinated Ti4+ ions contribute to the electrical conductivity and that the mobility of Ti4+ ions is almost equal to that of Ca2+ ions.
In the present study, a similar contribution of Ti4+ ion to electrical conductivity is obtained, although the conductivity varies markedly with the MnO/SiO2 ratio. Namely, when the ratio is small the ionic conduction result is a small value of electrical conductivity, where as when the ratio is larger than 2 the electrical conductivity rapidly increases. The increase in the electrical conductivity is considered to be due to the change from the ionic to electronic conduction. Furthermore, the mobility of Mn2+ ions is estimated to be nearly equal to that of Ca2+ ions.View full abstractDownload PDF (490K) -
Hakaru Masumoto, Kiyoshi Watanabe, Masao Mitera1978 Volume 42 Issue 2 Pages 169-172
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAn equilibrium diagram of Mn-19.0∼31.2 at%Ga binary alloys has been investigated by means of X-ray diffraction, thermal expansion and magnetic measurements. At room temerature the alloys show a βMn single phase at about 20.5 at%Ga or less, a β+ε mixed phase at 20.5∼25.0 at%Ga, and an ε single phase at 25.0∼29.3 at%Ga. With a further increase in Ga concentration, the ζ1 phase exhibits a phase mixture of ε+ζ1. It has been found that the intermetallic compound Mn3Ga does not exist in the equilibrium state.View full abstractDownload PDF (322K) -
Paul Hideo Shingu, Kunimasa Takeshita, Ryohei Ozaki, Tetsuo Akiyama1978 Volume 42 Issue 2 Pages 172-179
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe solidification of alloys has been treated as a heat conduction problem involving moving boundaries by many workers. However, the previous treatments of this problem needed a simplified assumption about the solid phase distribution in the freezing region. The necessity of making such assumptions is due to the fact that the solution for the treezing region is complicated because of an interdependence of the heat flow and the rate of solid phase formation. That is, the heat flow is modified by the generation of the latent heat of solidification the amount of which is dependent on the rate of solid phase formation which in turn is governed by the rate of heat extraction from the freezing region. The purpose of this work is to present a solution to this problem by taking into consideration the coupled effect of heat flow and the rate of solidification. The numerical solution for the freezing region is matched, through a trial and error method, with the analytical solutions obtainable for completely solid or liquid regions. The application of a numerical method for the solution of the freezing region can be possible because the rate of solid phase formation is expressed as a function of temperature by the application of the assumption of complete mixing of solutes within a small element in the liquid phase; the use of Scheil’s equation. As the result of calculations, not only the temperature change for the entire region and the velocities of moving boundaries, but also the solid fraction within the freezing region and the shape of the dendrites based on it were obtained. The results of calculations showed good agreement with the experiments using the H2O-NaCl system.View full abstractDownload PDF (563K) -
Susumu Satoh, Takeshi Mori, Hiroshi Fujita1978 Volume 42 Issue 2 Pages 179-185
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe behavior of coplanar slip in fcc metals has been examined in Cu-8 at%Al single crystals. Specimens used were rectangular plates so that the Burgers vectors of primary and coplanar slip were systematically controlled against the specimen surfaces. The results obtained are summarized as follows: (1) Since the latent hardening of secondary slip systems strongly occurs in the alloys, coplanar slip plays an important role for the relaxation of additional stress caused by the grip effect because of a weak interaction with the primary dislocations. (2) Activation of coplanar slip is determined by the ratio of Schmid’s factor of coplanar slip to that of primary slip rather than Schmid’s factor of coplanar slip itself. (3) When the tensile axis is close to the [\bar111]-[011] zone, coplanar slip is easily activated compared with other secondary slip. (4) Coplanar slip in stage II is observed to appear in the vicinity of the well-developed primary slip bands by electron microscopy. Coplanar slip in this stage of deformation contributes to the relaxation of the internal stress caused by primary slip.View full abstractDownload PDF (764K) -
Hiroshi Imagawa1978 Volume 42 Issue 2 Pages 185-190
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSome electrochemical aspects of the stress corrosion cracking (SCC) behavior of HT 80 steel in a liquid ammonia (99.9%) at 30°C have been studied. The measurement of electrode potential was made in reference to the Pt electrode. The results obtained are as follows:
(1) In liquid NH3 and NH3+0.5 wt%H2O, the “as-dipped” specimens exhibited a passive potential regardless of air contaminations, and the “cathodic treated” specimens showed an active potential except in a highly air-contaminating condition. The anodic polarization curves for steel showed no active-passive behavior in the above environments.
(2) In liquid NH3, SCC was observed when ever the potential was in an unstable active-passive region, and the potential suddenly shifted from the active to the passive direction by the addition of air but not by the addition of water or N2 gas. It is considered that the SCC is inhibited by the addition of O2.
(3) In a liquid NH3 in which SCC occurred in a field tanks, cracking was not observed in the dynamic slow strain rate testing procedure. This seems to be due to the effect of concentrated impurities in the field to assist the cracking.View full abstractDownload PDF (476K) -
Shinji Narishige, Mitsuo Sato, Masateru Suwa, Sadami Tomita1978 Volume 42 Issue 2 Pages 191-196
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe initial wear and effects of hardness, tape speed, tape tension and relative humidity on the wear of permalloys and SUS 304 by a lapping tape for magnetic head and by a magnetic tape have been investigated. The initial wear was found to result mainly from virginity of tape and partly from virginity of alloy. The wear did not vary with the hardness, tape speed and tape tension but remarkably with the tape brand and relative humidity. The humidity dependence differed by the tape brand and the alloy. When the relative humidity was varied from 50 to 60%, the wear of permalloys increased by more than two times while that of SUS 304 was almost unchanged. SUS 304 had higher wear resistance than permalloys under an identical condition. Alloy surfaces worn by tape were investigated by Auger electron emission spectroscopy. An oxygen enriched layer was found to exist in the alloy surface when the alloy was slightly worn by a tape. On the other hand, the oxygen-enriched layer was not found in the alloy which was highly worn.View full abstractDownload PDF (663K) -
Tooru Tsuru, Tomohisa Zaitsu, Katsumi Masamura, Shiro Haruyama1978 Volume 42 Issue 2 Pages 197-202
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAnodic behaviour of iron and iron oxides was studied in neutral and acidic solutions in order to determine the passivity of iron. The oxides exhibited passivity-like behaviour at the potentials corresponding to that of the passive state of iron. Cathodic chronopotentiograms of passivated oxides showed that the oxides were covered by a thin higher valent oxide of γ-Fe2O3, the thickness of which was comparable with that of passive iron. The impedance measurements of Fe, FeO, and Fe3O4, and the deposited γ-Fe2O3 in the passive potential region showed that the greater part of the applied potential appeared at the film-solution interface, and the faradic resistance at low ferequencies was of the order of 10−6 Ω, corresponding to the fact that there were no appreciable transfer reactions across the interface. Because the formation of passive films on oxides does not involve a dissolution process, it is found that the precipitation process, which is often regarded as a pre-passivation process, is not a necessary for the formation of a passive film, but inevitable for the potential of iron to shift to the passive region. The open-circuit decay of passive iron was attributed to the coupled reaction of the anodic oxidation of iron substrate and the cathodic reduction of γ-Fe2O3, both forming Fe3O4. The mechanism was confirmed by the fact that the passive films on FeO and Fe3O4 did not show any open-circuit decay.View full abstractDownload PDF (522K) -
Kouichi Maruyama, Tatsuo Fujita, Seiichi Karashima1978 Volume 42 Issue 2 Pages 203-209
Published: 1978
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe purpose of the present study is to make clear the effects of grain boundaries on mechanical properties in incompatible zinc bicrystal specimens. Two types of incompatible bicrystal specimens, one having a symmetric ⟨1\bar100⟩ twist boundary and the other having a so-called random boundary, were used in this study. The obtained results revealed that mechanical properties of incompatible bicrystal specimens were related to the degree of incompatibility as follows.
(1) The ratio of 0.1% proof stress in the bicrystal specimens to the theoretical one increases with the degree of incompatibility. The theoretical value was calculated on the basis of mixture law using values of 0.1% proof stresses of single crystal specimens having the same orientations with component crystals, respectively.
(2) With increasing degree of incompatibility the extent of the stage I work-hardening region decreases and the work-hardening rate of the region increases. The stress-strain curve eventually shows parabolic hardening behaviour throughout.
(3) Twinning deformation initiates at a very early stage of deformation in the bicrystal specimens. The amount of plastic strain at which twinning deformation begins to occur decreases as the degree of incompatibility increases.
From a detailed examination of the 0.1% proof stress data obtained from bicrystal specimens it was concluded that the back stress acting on dislocations of the primary slip system due to plastic incompatibility is one of the most important factors determining the proof stress.View full abstractDownload PDF (569K)
- |<
- <
- 1
- >
- >|