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Volume 49, Issue 10
Displaying 1-16 of 16 articles from this issue
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Utako Onose, Masashi Suezawa, Masato Imai, Koji Sumino1985 Volume 49 Issue 10 Pages 811-817
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDislocation-free crystals of high purity are needed for investigation of dynamic properties of dislocations. Kamada et al. succeeded to grow dislocation-free Nb crystals of diameters up to 0.5 mm in a vacuum of about 10−3 Pa. However, crystals with higher purity and larger dimensions are required for the above investigation.
In the present work, the technique of Kamada et al. was improved by employing an apparatus for the crystal growth by the pedestal method operating in an ultra high vacuum of 10−7 Pa which avoided the contamination of growing crystals from surroundings. Using zone-refined and degassed high purity Nb polycrystalline rods as pedestals, crystals with arbitrarily controlled orientations have been grown with this apparatus. According to examinations by means of X-ray topography utilizing the Borrmann effect, dislocation-free Nb crystals of diameters up to 1.1 mm have successfully been grown at speeds of 6.7×10−6-12×10−6 m/s.View full abstractDownload PDF (1248K) -
Akihiko Tachikake, Tsunenori Suzuki, Yoshitake Nishi, Etsujiro Yajima1985 Volume 49 Issue 10 Pages 818-824
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFor the purpose of studying the growth process of γ′ particles a supersaturated Ni-15 at%Al alloy was prepared by the liquid-quench method. The growth process was investigated by means of magnetic mass balance, transmission electron microscopy and field ion microscopy. It is definitely shown by this study that there were three stages in the precpitation and growth process of the γ′-particles.
In the first stage the γ′ phase was produced by nucleation or spinodal decomposion in the Ni-15 at%Al alloy.
In the second stage spherical γ′-particles were arranged at random in the matrix with the size independent of aging time. Then the Al concentration of the matrix decreased with (aging time)−1⁄3. The results suggested that the degree of ordering increased with aging time in the γ′ particles.
In the third stage the γ′-particles were coarsened with aging time. These particles were arranged in the (100) zone in the matrix and were cubic with the cube face lying on (100). The interfacial free energy was evaluated to be 28.4 mJ/m2 at 873 K and 22.4 mJ/m2 at 973 K. The diffusion coefficient of Al atom in the Ni matrix was 1.00×10−18 m2/s at 873 K and 3.69×10−20 m2/s at 973 K.View full abstractDownload PDF (1541K) -
Hiroshi Okuda, Kozo Osamura1985 Volume 49 Issue 10 Pages 825-831
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe phase decomposition process of dilute Al-Zn binary alloys aged at 274 K was investigated by means of the small-angle X-ray scattering (SAXS) method. Structural parameters such as radius of gyration Rg, integrated intensity Q, etc. were obtained from the scattering intensity for each specimen. It is found that the aging process at 274 K can be divided into three stages, I, II and III for all specimens studied here. In stage I, where the phase dicomposition developes, Rg lay between 0.3 nm and 0.6 nm. In stage II corresponding to the coarsening process, the 1/3 power law on Rg vs time was observed. Rg lay between 1.5 nm and 2.5 nm in stage III, where slowing down of the coarsening occurred. The scaling rule was successfully applied to the scattering intensity in stages II and III. From the discussion about the scaling behaviour on the basis of two-phase model, the half width of scaled structure function was pointed out to increase depending on volume fraction.View full abstractDownload PDF (924K) -
Yoshitaka Mori, Ishi Miura1985 Volume 49 Issue 10 Pages 832-838
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe morphology of two-phase grain structures have been studied by computer simulation on the basis of assumption of random nucleation sites and constant growth in two dimensions. Two-phase structures are generated by two models; nucleation and growth of both α- and β-phase to cover the whole region (model I) and nucleation and growth to limited fraction of α-phase in β matrix (model II). Various types of two-phase structures are generated by changes in nucleation law, growth rate, growth anisotropy given by ellipsoidal growth and growth direction.
In model I, two-phase structures generated in the condition that two nearest neighboring nuclei belong to different phases show structures similar to the actual two-phase structures which have less coaguration of grains of the same phase. In this structure, the ratio of boundary length between different phases to whole boundary length in the structure shows the maximum values of 60-70% at an identical area fraction of both phases. In model II, coefficients of variation of grain area distribution (CV) and the number of boundaries per one grain in the case of simultaneous nucleation model are increased with increasing fraction of generated phase and growth anisotropy. The CV values in the case of constant nucleation model are larger than those in the case of simultaneous nucleation model. The total length of different phase boundary show the maximum values at the fraction of generated phase of 0.3-0.4 in the case of simultaneous nucleation and of 0.4-0.6 in the case of constant nucleation. Two-phase microstructures in Fe-C alloy, Cu-Zn alloy, Ti-alloy and Al-Cu eutectic alloy are examined by comparison with the structures generated by computer simulation.View full abstractDownload PDF (2195K) -
Takuma Matsumoto, Rikuro Otsuka1985 Volume 49 Issue 10 Pages 839-846
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTo clarify the correlation between the hydrogen embrittlement and the hydride formation, cathodically hydrogen charged Ni-Fe and Ni-Co binary alloys with fcc structure have been investigated by means of X-ray diffraction and tensile test. The results are summarized as follows: (1) The hydrogen embrittlement of these alloys occurred always only when the hydrides were formed. (2) The degree of the embrittlement was dependent on the magnitude of the miscibility gap of the alloy-hydrogen systems and the amount of the hydride formed. (3) The embrittlement was enhanced by the dislocation transport of hydrogen. The enhancement was remarkable, when the amount of the hydride formed was small. (4) Hydrogen charging produced dislocations of high density and grain boundary microcracks in Ni specimens, only when the hydride was formed.
From these results the embrittlement was ascribed to the lattice expansion which accompanied the precipitation of the hydride phase as in the case of Ni-Cu and Pd-Ag alloys.View full abstractDownload PDF (1761K) -
Keijiro Nakasa, Xiaolie Chen, Hideo Takei1985 Volume 49 Issue 10 Pages 846-853
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDelayed failure tests were carried out on Ni-Cr-Mo steel quenched and tempered at 673 K in a NaCl aqueous solution in hydrogen charging condition, and the crack branching as well as crack propagation behaviors were investigated.
The crack propagation rate da/dt increases with increase in cathode charging current density, i, and da/dt increases to a maximum and then decreases with increase in the increasing rate of stress intensity factor, \dotK. The stress intensity factor at crack branching, KIB, decreases to a minimum and then increases with increase in i. These results can be explained by interaction between dislocations and hydrogen atoms, such as dislocation trapping and dislocation transport of hydrogen on the slip planes near crack tip.View full abstractDownload PDF (1071K) -
Takeo Segawa, Tetsuo Sato, Yasuo Kimura1985 Volume 49 Issue 10 Pages 853-859
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn this study, surface layers caused by rubbing of several kinds of copper alloy castings and their mating materials were analyzed with AES and EPMA to examine the relationships between frictional surface characteristics and load carrying capacity. Cu-Sn alloy castings (3∼20%Sn), lead bronze ones and tin bronze ones (Cu-5%Sn-5%Pb-5%Zn) were examined by sliding against carbon steel with a thrust type wear testing machine under conditions of boundary lubrication with SAE#30 lubricating oil, and their load carrying capacities were evaluated. Sulphur distribution on the surface was determined by using EPMA. Depth profiles of element concentration of the rubbing surface were obtained with AES. The relationships between element concentration in the rubbing surface and load carrying capacity were investigated.
The Cu-Sn alloy castings containing from 3 to 6%Sn had a good load carrying capacity. On their mating material surfaces against Cu-Sn alloys, copper was deposited thickly by transfer, and high sulphur concentration was observed in some places. This indicates that the antiseizure property and high load carrying capacity of Cu-Sn alloy depend on high sulphur concentration on the rubbing surface. In lead bronze, its mating surface was covered with tin and lead oxide film instead of copper in Cu-Sn alloys, and this film guarded against seizure and raised load carrying capacity. In tin bronze (BC6), zinc oxide was deposited by transfer on the mating surface, and consequently its load carrying capacity was poor.View full abstractDownload PDF (1567K) -
Takeshi Nagai, Yasuo Udo, Zenzo Henmi1985 Volume 49 Issue 10 Pages 860-864
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAtmospheric corrosion of various surface finished steels exposed at indoors and outdoors has been studied. Cold rolled, Zn electroplated and Zn hot dipped steels were finished by degreasing, dipping in a rust preventive oil, atomizing in a rust preventive reagent, conversion-treating and dipping in a rust preventive oil, and enamel coating. These specimens were exposed at five environments such as air-conditioned office and a roofed parking lot in a plant for 1100 days, and inspected visually.
Comparing an indoor corrosion rate with an outdoor one, a degreased cold rolled steel was corroded for a day at outdoors, but later stained for 1100d at an air-conditioned office. As a result, the degreased cold rolled steel was corroded at outdoors approximately 1000 times as fast as at indoors. The difference between the indoor and the outdoor corrosion rate is discussed.View full abstractDownload PDF (611K) -
Chemical Composition of Inclusions Observed in High-purity Iron Ingots Melted in an Alumina CrucibleTakehiro Dan, Noriyoshi Aritomi, Kazuyuki Ogawa, Yoshisuke Nakamura1985 Volume 49 Issue 10 Pages 865-870
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe purpose of the present work is to investigate the contamination of molten iron with crucible materials during the melting process.
High purity iron was melted at 1873 K for 900 s in an alumina crucible by use of a tungstenmesh heater furnace, and the ingot was subjected to the chemical analysis. The cross section of the ingot was deeply etched electrolytically and was observed with a scanning electron microscope. From the deeply etched cross section, inclusions were extracted onto a carbon film ancl the chemical composition was analyzed with an analytical electron microscope.
The results are as follows:
(1) Iron was contaminated with silicon during the melting process. The extent of the contamination depended on the silica content of the crucible.
(2) By use of an alumina crucible which contains silica by only 0.005 mass%, the contamination of melt was suppressed.
(3) The silicon content of inclusions depended on both the silicon and oxygen contents of ingots. It can be estimated by the equilibrium relationship and the change in melt composition during solidification.View full abstractDownload PDF (1029K) -
Katsutoshi Ono, Shoji Miyazaki1985 Volume 49 Issue 10 Pages 871-875
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTitanium with low oxygen content has been expected to be obtainable by direct reduction of titanium dioxide with saturated calcium vapor, because it can remove the oxygen to the extent to which it is able to overcome the affinity of the oxygen for the metal in the solid solution range.
A knowledge of the thermodynamic stability of oxygen in the Ti-O solid soluton is indispensable in any discussion of the refining of titanium from its oxide. Oxygen in titanium has, however, so high stability that ordinary gas equilibration or EMF method using solid electrolyte is not applicable to activity measurement. In this investigation, titanium metal was, therefore, equilibrated under coexistence of saturated calcium vapor and calcium oxide in closed bombs of steel at temperatures between 1173 and 1573 K, quenched and analysed for oxygen. The equilibrium gas concentrations were 300 and 900 mass ppm at 1173 and 1573 K, respectively. The data were then used to derive the relationship among oxygen potential, temperature and composition in the β-Ti phase field:
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Attempts were made to produce titanium by reducting TiO2 powders with saturated calcium vapors at 1273 K according to
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\ oindentElectron micrographs of the reduction products showed that the reduced titanium particles were completely surrounded with the solid reaction product, CaO. The reduction rate become very low at the reduction stage at which the decomposition of oxide almost ceased and the deoxidation of the Ti-O solid solution began to take place.View full abstractDownload PDF (1080K) -
Akiomi Kohno, Toshihiro Yamada, Kazuaki Yokoi1985 Volume 49 Issue 10 Pages 876-883
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBonding of non-oxide ceramics (pressureless sintered silicon nitride, silicon carbide and sialon) to metals with interlayers of aluminium clad with aluminium-silicon alloy was performed at high temperatures and at pressures in vacuum of 2-4×10−2 Pa. Bonding conditions, bending strengths and thermal stresses generated due to the difference in thermal expansion between ceramic and metal were studied. Bending strengths of the specimens were measured by means of four point bending.
Silicon nitride, silicon carbide and sialon were able to be bonded to metals by means of the interlayer of aluminium sheet clad with Al-10%Si alloy on both sides. High bending strengths were obtained in the specimens bonded in the temperature range between the melting point of the aluminium core and that of the Al-10%Si clad metal.
The bending strength was found to be influenced by the thermal expansion mismatch, thus it decreased with increasing difference in thermal expansion coefficient between ceramic and metal. Further, it is considered that other factors such as the parent strength, fracture toughness, the Young’s modulus of ceramic and the reaction products at the bonded interface also exert an influence on the bending strength.
Increase in thickness of the aluminium core of the interlayer was effective in the improvement of the bending strength. This improvement was explained by considering the relief of the thermal stress due to the softness of aluminium.
According to high temperature bend test, the bending strengths up to 573 K were as high as that at room temperature.View full abstractDownload PDF (1246K) -
Akihiko Kamio, Hiroyasu Tezuka, Shinji Kumai, Kenji Ono, Tsuneo Takaha ...1985 Volume 49 Issue 10 Pages 883-890
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMonotectic Cu-36 mass%Pb alloys were solidified unidirectionally in various growth conditions and quenched during growth to reveal the monotectic growth front. When the growth rate is high, the morphology of monotectic growth front is irregular and cellular. Pb rich L2 droplets which are produced by the monotectic reaction are successively trapped into cell gaps, and consequently, irregularly shaped rod-like composites form. When the ratio of temperature gradient to growth rate is increased, irregularity of the monotectic growth front morphology is reduced. Flatness of solid-liquid interface makes it difficult to trap L2 droplets into the solidifying interface, and coalesence and coarsening of L2 droplets ahead of the growth front are enhanced. A periodical banding structure consisting of Pb rich regions and Pb poor regions develops at the growth rate below 11.1×10−6 m/s at the temperature gradient of 6000 K/m. The addition of Al, Zn and Si to the Cu-Pb monotectic alloy increases the interfacial energy between L1 and L2 and reduces the coalescence and coarsening of L2 droples ahead of the monotectic growth front. A regularly aligned fibrous composite structure forms in those copper-base ternary monotectic alloys at high temperature gradient/growth rate ratio, as is the case with aluminum-base monotectic alloys. The copper-base and aluminum-base monotectic alloys have essentially the same growth mechanism.View full abstractDownload PDF (3475K) -
Hirobumi Okabe1985 Volume 49 Issue 10 Pages 891-898
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe oxidation behavior of an Fe-30 mass%Cr-4 mass%Al alloy and similar alloys containing 0.05, 0.09, 0.14 and 0.19 mass%Zr in still air over the temperature range of 1273-1573 K for 79.2 ks has been examined. The oxide formed on these alloys was mainly α-Al2O3, though the inclusion of ZrO2 particles in scales increased with an increase in zirconium content in the alloy. Oxidation kinetics and scale adherence were discussed in terms of the morphological details of the scales and the structural change in the scale-alloy interface. The addition of small amount of zirconium lowered the oxidation rate, but further zirconium addition tends to increase the oxidation rate by providing rapid diffusion paths in the form of ZrO2 stringers. The scale adherence, on the contrary, showed a reverse trend, i.e., the higher the zirconium content, the stronger the adherence in the experimental range tested. The present metallographic study revealed that in the case of alloys with good scale adherence, no voids were formed along the scale-alloy interface and many oxide stringers were formed.View full abstractDownload PDF (3051K) -
Satoru Taguchi1985 Volume 49 Issue 10 Pages 899-906
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of tensile stress on grain oriented electrical steel was studied in the thickness range 0.11-0.635 mm. The longitudinal magnetostriction increased drastically with increasing thickness. Below about 0.2 mm thickness, the decrease in core loss with tensile stress was greater for smaller thickness. Above about 0.25 mm, the decrease in core loss at high flux density, W17⁄50, with tensile stress was smaller for larger thickness, and the decrease in core loss at low flux density, W10⁄50 or W13⁄50, with tensile stress was larger for larger thickness. The decrease in core loss with tensile stress is due mainly to the decrease in the 90° domain volume. Disappearance of 90° domains caused by the tensile stress is more effective in lowering the coer loss at low flux density for larger thickness, because the volume of 90° domains at a demagnetized state is larger for larger thickness, and the volume of new 90° domains created at intermediate inductions is smaller at lower inductions. However, the volume of the 90° domains created at intermediate inductions is larger at higher inductions and larger thickness.
The decrease in core loss with tensile stress was greater for specimens with larger grain size, and the magnetostriction measurements indicated that the volume of the 90° domains at a demagnetized state and that of those 90° domains created at intermediate inductions were larger for specimens with larger grain size, because of reduction in the magnetostatic energy due to free pole appearance on the surface. The increase in core loss with larger grain size was due mainly to the increasing 90° domain volume.
When the ball pen scratching was applied, the decrease in core loss was larger for the specimens with larger grain size. The core loss with larger tensile stress was almost the same for the specimens with and without scratching except very high permeability specimens.View full abstractDownload PDF (2915K) -
Keiichi Kuniya, Hideo Arakawa, Tsuneyuki Kanai, Akio Chiba1985 Volume 49 Issue 10 Pages 906-912
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSWe have developed a new material of copper-carbon fiber composite which possesses the properties of copper, i.e., the excellent electrical and thermal conductivities, and the property of carbon fiber, i.e., a small thermal expansion coefficient. These properties of the composite are adjustable within a certain range by changing the volume and/or arrangement of carbon fibers.
The effects of volume and arrangement of fiber on the thermal conductivity, electrical conductivity and specific heat of the composite were studied. Results obtained are as follows:
(1) The thermal and electrical conductivities of the composite became smaller as the volume of carbon fiber increased, and were influenced by the fiber arrangement.
(2) The above results were predictable from a careful application of the “rule of mixtures” for composites.
(3) The specific heat of the composite was dependent not on the fiber arrangement but on the fiber volume.
(4) In the thermal fatigue tests, no degradation in the electrical conductivity of this composite was observed.View full abstractDownload PDF (832K) -
Hisashi Sekine, Yasuo Iijima, Kikuo Itoh, Kyoji Tachikawa1985 Volume 49 Issue 10 Pages 913-920
Published: 1985
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAddition of a small amount of Ti to the Cu-Sn alloy matrix of bronze-processed Nb3Sn superconductors has been found to remarkably enhance both the formation rate of the Nb3Sn layer and Hc2. Fundamental studies on the mechanism of increase in Hc2 and that in the Nb3Sn layer formation rate as well as metallurgical studies have been made. Composites consisting of Nb core and Cu-7 at%Sn-1 at%M (M=Ti, Cr and Fe), Cu-7 at%Sn-(0.2, 0.35, 0.5 and 1.5) at%Ti matrix alloys were worked into single-core wires 0.5 mm in diameter. Multifilamentary wires with different amounts of Ti addition to the matrix were also produced. Among additives of transition metals, Ti, Cr and Fe, only Ti showed large positive effects on the Nb3Sn layer formation rate and Hc2, while Cr and Fe showed negative effects on them. A small amount of Ti addition makes crystal grains of the Cu-Sn alloys very fine. The Ti addition also makes Nb3Sn crystal grains fine for the wires reacting at 1073 K, while it slightly coarsens Nb3Sn grains for the wires reacting at 1023 K. Hc2(4.2 K) shows the maximum when the Ti concentration in the Nb3Sn layer is between 1.0 and 2.0 at%. Measurements of the normal state resitivity, ρn, and (dHc2⁄dT)T=Tc together with calculations proved that the enhancement in Hc2 due to the Ti addition was caused mainly by the increase in ρn.View full abstractDownload PDF (1862K)
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