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Volume 54, Issue 10
Displaying 1-17 of 17 articles from this issue
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Koji Tanaka, Minoru Mori, Yoichi Ishida1990 Volume 54 Issue 10 Pages 1041-1050
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSStructure of Σ=3 incoherent twin boundaries in SUS316 austenitic stainless steels were analysed by the Weak-Beam α-Fringe Method. Fringe shifts at grain boundaries at common weak-beam diffraction conditions allowed the mesurement of the lattice translations between ajacent grains. The results showed that the (\bar211) boundaries or near (\bar211) boundaries are with a translation vector of a⁄12[2\bar1\bar1] and the (0\bar11) boundaries shifted by a⁄6[\bar1\bar1\bar1] with some exceptions. This a⁄12[2\bar1\bar1] translation conserves the common (111) plane as well as the atomic symmetry.View full abstractDownload PDF (3900K) -
Koji Tanaka, Minoru Mori, Yoichi Ishida1990 Volume 54 Issue 10 Pages 1051-1055
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt was reported that the Σ=3 incoherent twin boundary had some in-plane translation (mainly [111] direction) without appreciable excess volume. Previous Weak-Beam α-fringe observation, however, showed that many Σ=3 incoherent twin boundaries in SUS316 austenitic steel are with the a⁄12[2\bar1\bar1] translation. However, in these observations Weak-Beam α-Fringe dark field images by 111 diffraction showed an anomalous diffraction; α-fringe contrast appear or disappear depending on the sing of the deviation parameter \ bis. This image suggested a certain anomaly in the (111) plane. Computed images indicated that there is local translaion at the incoherent twin boundary by the curve of (111) atom plane and successive away from the boundary.View full abstractDownload PDF (1503K) -
Pi Zhi Zhao, Takao Kozakai, Toru Miyazaki1990 Volume 54 Issue 10 Pages 1056-1064
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSProcesses of phase separations into B2+DO3 or A2+DO3 at 873 K in Fe-Si-Ge ternary ordering alloys were investigated by TEM observations of microstructure and the free energies of all the relevant phases were evaluated. Sequences of phase separation from the A2 or B2 single phase state into the B2+DO3 or A2+DO3 equilibrium state were classified into five types. (1) In the alloys near the phase boundary B2/B2+DO3, continuous ordering from A2 to B2 occurs at first and then the DO3 phase is formed inside the B2 phase domains. (2) In the alloys near the phase boundary B2+DO3/DO3, continuous ordering from B2 to DO3 occurs at first and then the B2 phase is formed on the antiphase boundary of the DO3 phase. (3) In the alloys near the phase boundary A2/A2+DO3, the phase separation of A2 into A2+DO3 occurs directly without through any intermediate state. (4) In the alloys whose compositions are located in the centre area of the A2+DO3 field, phase decomposition from the B2 into B2+DO3 arises, followed by the phase separation into A2+DO3. (5) In the alloys near the boundary A2+DO3/DO3, continuous ordering from the B2 to DO3 phase occurs at first and then A2 phase is formed on the antiphase boundaries of DO3 phase. These sequences of phase separations could be explained from the hierarchy of free energies among the A2, B2 and DO3 phases evaluated on the basis of the Bragg-Williams-Gorsky approximation.View full abstractDownload PDF (4248K) -
Tadashi Yamada, Kyo-Han Kim, Byung-Nam Kim, Nobuo Takeda, Teruo Kishi1990 Volume 54 Issue 10 Pages 1065-1071
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe microstructure and mechanical properties of Ti-6Al-4V alloys can be changed by composition processes and/or heat treatment processes.
Several studies have been conducted to relate the microstructure to the static fracture toughness (KIc). Although Ti-6Al-4V alloys are being used under impact loading conditions, few studies have been conducted to evaluate the dynamic fracture toughness (KId). In this paper, KId values were obtained using the strain gage method with the Charpy impact test machine. The strain gage adhered close to a crack tip could be used to measure both the dynamic stress intensity factor and the crack initiation time, and then to calculate accurate and reliable KId values. Double solution treatment was used to change the microstructure of Ti-6Al-4V alloys, such as the acicular/equixed α phase fraction, and the shape and the size of the acicular α phase. Measured KId values, along with fracture surface observations, revealed some micro-fracture mechanisms to contribute the increase in KId, and the effects of the above microstructure. The KId values always increased with the increasing impact velocity. The higher KId values were obtained with the higher acicular α phase fraction or with the shorter and/or thinner acicular α phase. It was found that the number of small quasi-cleavage fractures increased and the fracture surface became much rougher for materials with the higher KId values.View full abstractDownload PDF (2528K) -
Ryouichi Ichino, Masazumi Okido, Takeo Oki1990 Volume 54 Issue 10 Pages 1072-1077
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe surface reaction uniformity of the copper electrode was studied by using the interfacial impedance method, and the change of the surface uniformity with the addition of various concentrations of some additives was discussed. The additives were sulfic acid, benzotriazole (BTA), gelatin, tiourea, nonyl-phenyleicosa-ethylene-glycol-ether (NP-20) and sodium chloride. According to the Cole-Cole’s law, when the surface of the electrode was heterogeneous, the impedance diagram was semicircular with its center under the real axis. The angle, θ, between the horizontal axis and the center of the semicircle was related to the surface reaction uniformity. The uniformity was discussed in terms of Rp, θ and the time constant τ0. Rp, θ and τ0 decrease with increasing sulfic acid. With increasing additions of BTA, gelatin, tiourea and NP-20, Rp and τ0 increase and θ decrease. The increase of Rp or τ0 suggests the decrease of the effective reaction area or the inhibition of surface reaction. With increasing additions of the additives, the reaction uniformity of the electrode surface was higher, but the activity became higher in the case of sulfic acid and lower in the case of BTA, gelatin, tiourea and so on. The above results show that the impedance method is available for assessment of the surface reaction uniformity and the surface activity.View full abstractDownload PDF (706K) -
Satoshi Sunada, Hidetoshi Maesato, Yoshio Yokoi, Hisakimi Notoya, Sumi ...1990 Volume 54 Issue 10 Pages 1078-1086
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of the deformation-induced martensite (α′) on the pitting corrosion of Type 304 austenitic stainless steel in H2SO4-NaCl solution was investigated by means of electrochemical measurements and optical microscopic observation.
The main results obtained are summarized as follows:
(1) The pitting corrosion resistance of SUS304 steel decreases with an increase in the volume fraction of martensite. The pitting corrosion resistance also decreases with increasing solution temperature and NaCl concentration.
(2) The effect of martensite on the number of pits of SUS304 steel depends upon the NaCl concentration, temperature and potential. In the case of high NaCl concentration, the amounts of pits increase lineally with increasing volume fraction of martensite in SUS304 steel. Under high temperature and high anodic potential conditions, the amounts of pits are almost constant in the range of the volume fractions of more than 50%.
(3) The pitting corrosion rates increase as the concentration of NaCl, the anodic potentials and the temperature of the solution are increased. The concentration of NaCl and the anodic potentials affect the amounts and growth of pits, while the temperature affects only the amounts of pits.View full abstractDownload PDF (1333K) -
Wataru Ito, Takahiro Higashijima, Hisakazu Ezaki, Masahiko Morinaga, N ...1990 Volume 54 Issue 10 Pages 1087-1093
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe anodic polarization behavior of commercially pure Zr, Zircaloy-2 and Zr-M binary alloys (M=Sn, Fe, Ni, Cr, Mo, Ti, Hf, Nb) was investigated in 20 mass% sulfuric acid at 303 K. The corrosion current densities were measured with changing potential at a constant rate of 0.33 mV/s from the corrosion potential to 1.5 V (SCE).
For pure Zr and its alloys those active noses which appear in stainless steel were not observed in the polarization curves. The measured curves were classified into two types. The first type was characteristic of the monotonous change of the current densities with potential. This type was observed in pure Zr and Zr-Sn, Zr-Fe, Zr-Ni, Zr-Ti, Zr-Hf and Zr-Nb alloys, in which there was either a Zr-rich precipitate or non-precipitate. The other type was characteristic of the appearance of a peak in the current densities at a certain potential. This type was observed in Zircaloy-2, Zr-Cr and Zr-Mo alloys, containing Cr or Mo rich precipitates. It was found that the peak occurred owing to the dissolution of such precipitates. The peak height increases with the increase in alloy composition. The boundary compositions at which the precipitation reaction takes place in the alloys were estimated rather accurately from the measurement of the anodic polarization curve.View full abstractDownload PDF (1240K) -
Shotaro Morozumi, Kouichi Nanjyo1990 Volume 54 Issue 10 Pages 1094-1098
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSince molybdenum can be corroded easily in distilled water and dissolved as ions, the effect of various additives such as acid, alkali and salt is investigated by measuring absorbance of a light with a wavelength of 460 nm, in order to obtain any information on inhibitors for corrosion of the metal in aqueous solutions, as well as on the effect of contact with several base metals on the corrosion. Results obtained are as follows:
(1) Among innorganic acids, only HCl can inhibit the corrosion, and its optimum concentration is 5 mol·m−3. Organic acids can inhibit the corrosion appreciably.
(2) Addition of alkali, NaOH, to the water enhances the corrosion.
(3) Addition of salts to the water generally inhibits the corrosion with few exceptions. Among the salts, AlCl3 and BaCl2 have an excellent inhibitor effect at their appropriate concentration, respectively.
(4) The inhibitor effect of potassium dichromate, K2Cr2O7, is superior to that of AlCl3 and BaCl2. However, the optimum concentration of K2Cr2O7 in the water can be reduced from 3 to 0.1 mol·m−3 by the addition of 100 mol·m−3 AlCl3, keeping the same effect.
(5) A base metal such as Al can inhibit the corrosion when it is in contact with molybdenum in the water.View full abstractDownload PDF (604K) -
Hisao Esaka, Toshio Shimada, Shozo Mizoguchi, Hiroyuki Kajioka1990 Volume 54 Issue 10 Pages 1099-1105
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe formation mechanism of equiaxed grains during solidification has been investigated in Fe-Ni alloys, since the diffusion coefficient of nickel in the solid iron is small and this system has the peritectic reaction as the Fe-C system does. Alloys were melted in the vacuum induction furnace and the melt was cast in the ingot mold made of MgO. In this ingot mold, fine thermocouples covered by thin quartz tubes were set to measure the temperature change. The ingot was cut and metallographically investigated. The equiaxed ratio was then measured as a function of superheat and nickel content.
When superheat was less than 50 K globular grains were found independent of composition. In the center of the globular grains, a higher concentration region was found in the alloys with high nickel contents in which the γ-phase was solidified as a primary phase. The globular grains found in this study are formed by the nucleation in the slightly undercooled alloy melt. The mathematical model for nucleation has been also established to estimate the value of the undercooling and concentration difference. The result of this model agrees well with the result of temperature measurement.View full abstractDownload PDF (1086K) -
Yasunori Miyata, Yoshiteru Izumi, Mitsugu Matsushita1990 Volume 54 Issue 10 Pages 1106-1111
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSViscous fingering experiment is performed as a hydrodynamic analog of metallic dendritic growth under the influence of linear anisotropy through a straight groove. A single finger on a groove always tends to grow faster, accompanied by side branches. The profile of a finger tip is approximated by a parabola. The tip radius of curvature depends on the growth velocity by power −1⁄2. The width of the primary stem and the first secondary-arm spacing have scaling behaviour with the tip radius of curvature. The equations and boundary conditions in the growth of viscous finger correspond well to those in solidification of metals, if the pressure in the finger growth is replaced by the temperature in the solidification in the equations. Therefore, the experiment for viscous finger would become a good modelling experiment for the dendritic growth in solidification.View full abstractDownload PDF (1180K) -
Takashi Shibata, Yoshiro Ishii, Kuniaki Kobayashi1990 Volume 54 Issue 10 Pages 1112-1119
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTitanium nitride films were deposited on tool steel substrates (JIS SKH51) by DC plasma-assisted chemical vapor deposition. TiCl4, N2, and H2 were used as the reactant gases at a total pressure of 133 Pa. The deposited films were widely investigated for the relationship between N2 flow rate at constant TiCl4 and H2 flow rates and properties of the films; namely, optical, mechanical, structural and compositional properties. Plasma diagnostics was also performed by using a quadrupole mass spectrometer and an optical emission spectrometer in order to investigate the mechanism of titanium nitride formation.
It was found that the properties of the deposited films changed systematically with N2 flow rate, and there was an optimum value for desirable properties. The values ranged from 1.67×10−6 m3·s−1 to 3.33×10−6 m3·s−1 in N2 flow rate and from 2 to 4 in N2/TiCl4 flow rate ratio. The results indicate that in the range of N2 flow rates below the optimum value, the film properties are affected by the change of the N/Ti ratio, and above the optimum value, by the change of the film structure. Plasma diagnostics suggested that the main species concerned with titanium nitride formation might be Ti and/or Ti+ and NHx(x=1−3). Based on these results, the following model has been proposed. The reactant gases are partially decomposed and activated in a DC positive column to some extent, and the mainly activated in a cathode sheath resulting in the formation of Ti and/or Ti+ and NHx, which may be precursors for the formation of titanium nitride.View full abstractDownload PDF (1287K) -
Shigeru Yonetani, Katsuya Imai, Hisakimi Notoya1990 Volume 54 Issue 10 Pages 1120-1130
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSResidual stresses in the steel sheet specimens cold-rolled from 20 to 67% total sectional reductions were measured. Used specimens were hot-rolled sheets which had the thickness of 5.0 and 3.2 mm. In cold-rolling, two different roll sizes, 250 and 75 mm in diameter, were used and the reduction per pass was 20%. Textures in the sections of these specimens were measured. Normal residual stresses along the rolling and transverse directions are tension in the outer parts and compression in the inner parts of these specimens, and the residual stresses in the surface is compression in the case of the rolling condition with large diameter rolls. On the residual stress distribution in the specimens rolled with large diameter rolls, the effect of the residual stress existing before rolling vanished over 40% reduction, and the same tendencies were observed in the specimens by heavy reductions. The residual stress distribution in the sheet after rolling by large diameter rolls differ from the one by small diameter rolls. The residual shearing stresses in the section of these specimens vary depending on the increasing reduction. The influence of the structure for the generation of residual stress on rolling was discussed.View full abstractDownload PDF (1756K) -
Kazuyoshi Kamachi, Tsutomu Yamamoto1990 Volume 54 Issue 10 Pages 1131-1135
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe feature of cemented carbide is in the high hardness and it shows little plastic deformation before fracture by external forces, and the fracture strength is generally discussed in terms of the internal defects such as voids, produced in the production process of the powder metallurgy. The voids are regarded as the initial triggering points of cracking and act as stress concentrator. The probability of existence of these voids and their shape, size and distribution should be treated in a statistical manner and the fracture strength of these defective brittle materials must be considered in statistical processes. When some significant differences are appeared in the fracture strength of the brittle materials, the causes of the differences should be searched in other factors than the defects. In this study, the differences of the fracture strengths of WC-(5.5∼15)%Co alloys owing to blasting with other sorts of the blasting media were studied from the stand-point of residual stress measurements comparing with the surface conditions. As the result of the experiments, it was made clear that the difference of the facture strength of the cemented carbides blasted with the other sorts of blasting media would be based on the difference of the residual stresses produced by the blasting and the residual stresses of compression were discussed in terms of the hardness of the blasting media.View full abstractDownload PDF (1355K) -
Naoshi Ikeda, Koji Emura, Masao Itabashi, Koji Hayashi1990 Volume 54 Issue 10 Pages 1136-1141
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe sinterability, thermal expansion coefficient (α) and room temperature transverse-rupture strength of invar-cordierite sintered composites which were prepared from iron, nickel and cordierite fine powders were investigated in relation to the additional amount of boron as a sintering aid, the volume percentage of cordierite, sintering temperature, etc.
The results obtained were as follows: (1) The sinterability was improved by the addition of boron more than 0.2 mass% (vs. invar) especially in the case of inadequite milling. The compact with 10∼90 vol% cordierite almost completely densified by sintering at 1623 K for 7.2 ks. (2) The α decreased with cordierite content, following the rule of mixtures, and the average values between room temperature and 673 K or 873 K, for example, at 50 vol% was 4.2 or 5.8×10−6 K−1, respectively. These values were fairly smaller than those of invar (7.4 or 9.7×10−6 K−1). (3) The strength decreased with cordierite content above about 20 vol%, which would be due to the coarsening or skeleton formation of brittle cordierite phase. The value of 310 MPa, however, was obtained even at 50 vol%.View full abstractDownload PDF (2790K) -
Toshio Narita, Kazuma Miura, Isao Ishikawa, Tatsuo Ishikawa1990 Volume 54 Issue 10 Pages 1142-1146
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSResidual thermal stress on the ceramics joined to metals was determined with a reflection-type acoustic microscope. This report is concerned with an apparatus for measuring surface acoustic wave (SAW) propagation velocity and an analytical method for determining residual thermal stress from the change in SAW velocity as well as the results obtained for the silicon nitride ceramics joined to stainless steel with Ni/W/Ni interlayers.
The maximum stress in the vicinity of the ceramic/metal interface, which was tension in nature, was estimated to be 400, 200, and 600 MPa for joints with 0.5 mm Ni (A), 1.25 mm Ni (B), and 2.0 mm Ni (C) interlayers. The stress decreased gradually with the distance from the ceramic/metal interface for the joint C, whereas for the joint A the stress profile was complex, showing a small compressive stress at a distance of 0.7 mm and a maximum tensile stress between 1 and 2 mm. For the joint B, the tensile stress was relatively low all over the ceramics. A four-point bending test at room temperature showed that joints A and C had a relatively low fracture strength, while the joint B had the highest strength of 230 MPa, because of low residual thermal stress.
It is proposed that the scanning acoustic microscope shows considerable promise for the non-destructive evaluation of the stress and stress distribution at the ceramic surface of ceramic/metal joints.View full abstractDownload PDF (737K) -
Takuhiko Nishida, Tatsuo Yamazaki, Susumu Chida, Masao Yamamiya1990 Volume 54 Issue 10 Pages 1147-1153
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of addition of master alloy powders containing B on the densification, microstructure and mechanical properties of atomized iron powder compacts has been studied.
The results are summarized as follows.
(1) The Ni-B master alloys activated the sintering process through the formation of eutectic liquid. However, there was limitation to sintered density that was attained by those alloys.
(2) Densities of the order 99% theoretical were readily achieved with addition of the Fe- Ni-B master alloy powders. Volume fraction of liquid phase was increased during the sintering process by addition of these additives.
(3) Rapid densification occured at 1403 K in iron powder compacts from 16 μm and at 1423 K from 80 μm, but in compacts from 45 μm having large pore size distribution occurred above 1433 K.
(4) Sintered strength increased with the amount of master alloy powders. With 5% additive, the tensile strength of 400 MPa was obtained. Maximum elongation of 30% occurred at 2% addition.
(5) Elongation was closely related to the forming process of the eutectic phase and decreased as it became continuous since a fracture occurred along the eutectic structure.View full abstractDownload PDF (1748K) -
Shinichi Orimo, Hironobu Fujii, Kenichi Yamamoto, Kazuyuki Yoshimoto, ...1990 Volume 54 Issue 10 Pages 1154-1163
Published: 1990
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn most applications of metal hydrides, breaking into a very fine powder upon hydriding is one of the important problems to be solved. In this paper, we have developed new composite materials for hydrogen storage which contain LaNi5, Zr(Fe0.7Cr0.3)2 or TiMn1.5 as the storage material and magnesium as a binder. The influence of composition, compacting pressure and heat treatment on the storage capacity and the stability behaviour of the pellets was investigated by repeating absorption-desorption cycles. The pellets obtained by sintering the mixture of Zr(Fe0.7Cr0.3)2 and Mg powder at 773 K for 20 h absorb hydrogen easily and very fast under hydrogen pressures less than 1 MPa without any special activation treatment, and exhibits no significant decrease in hydrogen storage capacity without any disintegration after 1000 hydrogen absorption-desorption cycles. In order to clarify the origin of the improvement, we observed the microstructure and the distribution of the metals and oxygen atoms in the composite by SEM, EPMA and ESCA. The results indicate that the heat treatment at 773 K for 20 h not only promotes the so-called Mg reduction and makes the surface of the hydrides clean, but also it helps form a new thin composite phase on the boundary between the hydride and Mg metal, which acts as a binder, remaining the pellet intact upon hydriding.View full abstractDownload PDF (2603K)
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