Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 52 , Issue 12
Showing 1-18 articles out of 18 articles from the selected issue
  • Fukuji Inoko, Minoru Kobayashi, Atsushi Sejima, Kohei Tatsumi, Masahir ...
    1988 Volume 52 Issue 12 Pages 1169-1178
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The formation of recrystallized grains at grain boundaries was examined in orientation-controlled copper bicrystals in which primary screw dislocations in one component crystal and primary edge dislocations in another were parallel to the large angle grain boundary planes. Copper bicrystals with 99.99 mass% purity were prepared by using the modified Bridgman technique. All bicrystals were pulled in tension by the strain of 3×10−1 at room temperature and annealed mainly at 623 K for 300 s under vacuum. It was found that many recrystallized grains were formed at the grain boundaries either by the ⟨111⟩ rotation of the deformed matrix or by the strain induced boundary migration (SIBM). Twin-relationships were mainly observed between the deformed matrix and recrystallized grains, and occasionally between recrystallized grains. The relationships were more prominent in the copper bicrystals with the lower stacking fault energy than in the aluminum bicrystals with the higher one. The ratio of the recrystallization temperature at the grain boundary to the melting point, TReTM, was approximately 0.46 in the present study while 0.81-0.85 in the previous study in aluminum bicrystals. The ratio in the copper bicrystals is only half of that in the aluminum bicrystals. The present study supports the conclusion generally accepted that recrystallized grains form preferentially at grain boundaries by two mechanisms, namely, the ⟨111⟩ rotation and the SIBM in intermediately deformed fcc pure metals. The heavy pile-up of screw dislocations at grain boundaries promotes the ⟨111⟩ rotation, while that of edge dislocations promotes the SIBM. In the case of the ⟨111⟩ rotation, the twinning is more prominent with lowering stacking fault energy.
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  • Naoto Yoshimi, Hideo Nakae, Hidetoshi Fujii
    1988 Volume 52 Issue 12 Pages 1179-1186
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    As the fundamental study of wetting phenomena accompanied by a solid/liquid interface reaction, the contact angle θ of liquid Al drops on sintered MgO (purity: 96.85%) was measured in an atmosphere of He+3%H2 at 1173∼1333 K.
    From the changes of θ on a logarithmic scale of time, it has become clear that the wetting of this system has three stages as follows.
    (1) Early stage. (2) apparent steady stage, and (3) contact angle decreasing stage accompanied by chemical reaction. And the reaction zone is a spinel structure (MgO·Al2O3).
    Further, by investigating the changes of contact angle θ and solid/liquid interface diameter 2x, it has been confirmed that the third stage has the following two cases: (1) with spread (advancing contact angle) and (2) without spread (receding contact angle).
    Therefore it is proposed that the condition of wetting extension is defined as
    dθ⁄dt<0 and d(2x)⁄dt>0
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  • Jun-ichi Echigoya, Satoshi Tagashira, Hajime Suto
    1988 Volume 52 Issue 12 Pages 1187-1191
    Published: 1988
    Released: April 04, 2008
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    Pt and (001)Y-stabillized ZrO2 were welded. HREM reveals that the Pt/c-ZrO2 was directly bonded without any amorphous and reacted phases between their interfaces. The orientation of Pt particles on (001)c-ZrO2 was randomly distributed, so that no particular orientation relationship could be found by the ECP studies.
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  • Serge Hagege, Shun-ichiro Tanaka, Yoichi Ishida
    1988 Volume 52 Issue 12 Pages 1192-1198
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Structure of planar defects with unique appearances in hot-pressed wurtzite AlN was examined by weak-beam and high resolution electron microscopy to understand its nature and the growth mechanism. Condensation of supersaturated vacancies during cooling of the specimen is considered as the major driving force for expanding both the stacking fault type planar defect parallel to (00·1) and curving one constituting the composite structure, although cooperating effects of major impurity elements such as oxygen by segregating into the faulted defects is also suspected. The growth configuration of the defect composite indicated that internal stress in the hot-prerssed specimens affected the selection of variants of the faulting defect parallel to the basal plane.
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  • Shigeo Sugawara, Jirô Watanabé
    1988 Volume 52 Issue 12 Pages 1199-1205
    Published: 1988
    Released: April 04, 2008
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    The dissolution at edge dislocation sites on the Cu (111) surface was studied as a function of concentration of inhibitor NH4Br in Young’s solution. The dissolved thickness S of the matrix surface was measured by the two-beam interferometry and the width h and depth d of dislocation etch pits formed were measured by replica electron microscopy. The net dissolved amounts along lateral and normal directions at the dislocation sites, H and D, were determined from S, h and d, respectively.
    As the concentration of NH4Br in the etchants increased, H decreased remarkably, and D attained a maximum value at its medium concentration. On the other hand, S was almost unchanged by varying the NH4Br concentration. It was shown that these results could be explained qualitatively on the basis of the two-dimensional nucleation theory of crystal dissolution by considering the variations of the adsorption fraction of poisons, the interfacial energy and the difference in chemical potential when the concentration of NH4Br was increased.
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  • Masahiko Ikeda, Shin-ya Komatsu, Takashi Sugimoto, Kiyoshi Kamei
    1988 Volume 52 Issue 12 Pages 1206-1211
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Negative temperature dependence (NTD) of electrical resistivity (ρ) was investigated on several Ti-Nb alloys quenched from 1073 K in relation to α″ martensite and athermal ω phases.
    The estimation of starting and ending temperatures of the athermal ω formation, ωs and ωf, respectively, was attempted with special care to avoid the reverse transformation of the α″ phase and the decomposition of the retained β phase.
    The α″ was observed in the 20∼35%Nb alloys, and in the alloys with more than 40%Nb only the retained β was observed. The NTD was observed only in the 40%Nb alloy, and both a maximum and a minimum of ρ appeared in the temperature range of 77∼350 K. This supports the previously proposed model for the resistivity change during the athermal ω formation.
    The values of ωs and ωf estimated from resistivity temperature curves decreased with Nb content. The composition range of alloys, in which the so-called quenched ω phase was observed, coincided with that of the alloys which was intermediate between ωs and ωf at room temperature.
    Therefore, the “quenched ω” may be the athermal ω with a large volume fraction at room temperature.
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  • Takehide Senuma, Hiroshi Yada, Ryou Shimizu, Masao Matsuo, Jirou Haras ...
    1988 Volume 52 Issue 12 Pages 1212-1220
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Textures of warm rolled low carbon and Ti-bearing ultra low carbon steel sheets have been investigated. The main orientation of the recrystallization texture of the low carbon steel sheet is near {114}⟨110⟩, while that of the Ti-bearing ultra low carbon steel sheet is near ND\varparallel⟨111⟩.
    To explain the different formation of texture between the steels, their recrystallization behavior has been studied in detail. The study shows that the low carbon steel preferentially recrystallizes from near ND\varparallel⟨100⟩ grains, and the Ti-bearing steel from near ND\varparallel⟨111⟩ grains. The difference in the preferential nucleation site relates with the recrystallization retarding effect.
    Microtextural measurements by electron channeling pattern reveals that the orientation of grains recrystallized in the vicinity of grain boundaries between two near ND\varparallel⟨111⟩ grains greatly differs between the two steel. This difference yields by carbon in solution. A further study using transmission electron microscopy and selected area electron diffraction shows that in the presence of carbon in solution, {114}⟨110⟩-{112}⟨110⟩ orientations are formed in the vicinity of grain boundaries by some unique crystal rotation different from that occurring in the matrix. The occurrence of the unique crystal rotation is explained by the variation of active slip systems due to the interaction between dislocations and the interstitial atoms by work hardening.
    It is concluded that the essential factors affecting the formation of the recrystallization texture of warm rolled sheets are carbon in solution and the retarding effect on recrystallization.
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  • Mamoru Yamada, Makoto Kato
    1988 Volume 52 Issue 12 Pages 1221-1227
    Published: 1988
    Released: April 04, 2008
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    Stoichiometrical mixture of iron, ferric oxide and silica to fayalite was prepared and mixed with 5 mass% alumina. The tablets formed by pressing the mixture were fused at 1523 K for 1.8 ks in an argon atmosphere of about 20 Pa oxygen partial pressure, and coagulated rapidly and slowly. The coagulation structures of the iron-silicate were observed and analyzed with EPMA. Under the rapid coagulation, the following phases were observed; lamellar fayalite, fine lamellar structure of the FeO-SiO2 system and slag containing fine dendritic precipitates of nonstichiometric hercynite or fine grains of magnetite. On the other hand, the phases of lamellar fayalite, dendritic or plate precipitates of nonstichiometric hercynite and slag were observed on the specimen coagulated slowly. In slow coagulation structure, the ratio of FeO to SiO2 of FeO-Al2O3-SiO2 slag is smaller than that in the rapid one, and both of the ratio of FeO to Al2O3 and the TiO2 content of plate precipitates are smaller than those of the dendritic one. The coagulation process of the iron-silicate melts was discussed on the basis of structural observations of backscattered electron images, the estimation of valency state of cation from the chemical shift of the spectra of characteristic X-rays, and the determination of oxygen content using the analyzing crystal, LDE1.
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  • Masamichi Miki, Yoshikiyo Ogino
    1988 Volume 52 Issue 12 Pages 1228-1237
    Published: 1988
    Released: April 04, 2008
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    Formation, growth and structural change of grain boundary cells in a Cu-25 mass%Ni-15 mass%Co spinodal alloy on aging at 673-923 K after quenching from 1373 K were investigated by means of optical and electron microscopic observations, and X-ray measurements. This alloy decomposed spinodally during quenching. Cell formation was also observed in the as-quenched specimen. On the following aging, cells grew at a constant rate and engulfed completely the matrix before the matrix hardness reached the maximum value. Modulated structure was observed in the cells, and the amplitude and wavelength of the modulated structure increased with progress of aging. The apparent activation energies for the growth of the cell and the modulated structure in the matrix were 132 kJ/mol and 194 kJ/mol, respectively. It is considered that the cell formation in this alloy results from the preferential increases in amplitude and wavelength of the spinodal structure nearby grain boundaries owing to rapid grain boundary diffusion.
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  • Katuo Saitou, Yasuo Otoguro, Junji Kihara
    1988 Volume 52 Issue 12 Pages 1238-1245
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    In the previous studies of the discontinuous deformation, little attention has been paid to the effect of the stiffness of testing machines and specimens. The purpose of this experiment is to study the effect of the stiffness of the testing system on the discontinuous deformation. In paticular, the stress drop and the time interval which characterize the discontinuous deformation are taken into consideration.
    The experiment was carried out at room temperature using the 7075-Al alloy as the specimen.
    The main results obtained are as follows:
    (1) The plastic elongation due to load drops increases with increasing elastic potential energy of the testing system, while the average plasic strain increases depending on the ratio α of the spring constant of the specimen to that of the machine.
    (2) The stress drop and the time interval depend on the spring constant ratio, which may be expressed as Δσ=Δσ0(1+k(ε,\dotε)·α) and Δt=Δt0(1+k′(ε,\dotε)·α).
    (3) The follwing relation holds when the stress drop and the time interval are extrapolated to α→0, Δσ0=f0\dotεΔt0, where f0 means a tangential hardening rate of the stress strain curve and its value is approximately equal to 0.4E.
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  • Ying-Hwa Yeh, Hideharu Nakashima, Hiroaki Kurishita, Shoji Goto, Hideo ...
    1988 Volume 52 Issue 12 Pages 1246-1254
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    High temperature creep of dispersion-strengthened Al-1.5 vol%Be alloys has been studied over a stress range 3.1×10−5∼5.9×10−4E(E: the Young’s modulus of Al matrix), which corresponds to 0.38∼6.6σoror: the Orowan stress), at temperatures from 473 to 723 K. It is found that there occurs a threshold stress for creep deformation, σth, and the value of σth is approximately equal to that of σor and their ratio, σth⁄σor, is almost independent of the particle size and test temperature. At stresses below σth, plastic deformation of very slow rates takes place which may be associated with grain-boundary sliding and diffusion creep. In-situ HVEM observation reveals that the interaction between dislocations and particles is of attractive type and no dislocation line is visible at the particle/matrix interface, indicating that the stress field of a dislocation is almost completely relaxed at the interface. The observed threshold stress is discussed from the viewpoint of the attractive interaction.
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  • Ying-Hwa Yeh, Hideharu Nakashima, Hiroaki Kurishita, Shoji Goto, Hideo ...
    1988 Volume 52 Issue 12 Pages 1255-1262
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    In order to examine the validity of Srolovitz’s attractive interaction theory in dispersion-hardened alloys, high-temperature creep behavior of Al-0.7 at%Mn alloy has been studied in a wide stress range covering both sides of calculated Orowan stress. It is found that a clear threshold stress for creep deformation occurs. The stress is approximately equal to the stress estimated from the attractive-interaction hardening, σv, which is nearly equal to the Orowan stress in this alloy. TEM observation also suggests that the interaction between dislocations and Al6Mn particles is of attractive type. Further, it is shown that the threshold stresses reported so far in dispersion-hardened alloys are well explained by the attractive interaction. Stress dependence of steady-state creep rate is very different between the high and low stress regions, the stress exponent, n, being 14∼21 and 4, respectively. The stress dependence of n is commonly observed in dispersion-hardened alloys. Their boundary stress increases with decreasing temperature, and the activation energy for creep deformation, Qc, in the high stress region is much higher than that for self diffusion in pure Al, while the value of Qc in the low stress region is nearly equal to the activation energy for pipe diffusion. These values of n and Qc are discussed on the basis of available theories.
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  • Toshio Shimoo, Yasushi Sakai, Shigeru Ando, Hiroshi Kimura
    1988 Volume 52 Issue 12 Pages 1263-1269
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    In relation to hot metal pretreatment by soda ash, the vaporization of Na and S from sodium silicate slags has been investigated. At temperatures between 1623 and 1773 K, the slag was melted in a graphite crucible under an atmosphere of argon. The amount of Na and S generated was determined by thermogravimetry and chemical analysis.
    The rate of Na vaporization from Na2O-SiO2 slag is approximately represented by the first-order-type rate equation. The rate constant increases with increasing slag basicity, i.e. the (%Na2O)/(%SiO2) ratio, and the activation energy varies from 230 to 250 kJ/mol. It is considered that the vaporization would be controlled by the chemical process.
    Both Na and S evaporate from Na2O-SiO2 slags containing Na2S. Particularly in the acid slag, the most of the mass loss measured is due to the vaporization of Na2S. The vaporization of S is retarded by an increase in the slag basicity, but the reduction of Na2O at an early stage is accelerated by the addition of Na2S to the high basic slag.
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  • Tetsuya Akiyama, Toshio Terasaki
    1988 Volume 52 Issue 12 Pages 1270-1275
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The nondestructive method to predict the time when the austenitic stainless steel welded joint exceeds a critical degree of sensitization at a low temperature is investigated by the mathematical model and experimental tests.
    The material used in this experiment is type 304 stainless steel without cold working. To measure the degree of sensitization, the electrochemical potentiokinetic reactivation (EPR) test was used. To determine the intergranular etch ratio, the 10% oxalic acid etch test was employed.
    From the mathematical analysis, the following results were obtained. The time when welded joint exceeds a critical degree of sensitization is predicted from the results of the accelerated test with the test pieces having the intergranular etch ratio similar to that of the welded joint at a temperature below 873 K. In the case where the intergranular etch ratio of welded joint is less than 0.7, this method is useful.
    From these experimental tests, we were able to predict the time using the method based on the mathematical analysis.
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  • Toshinori Ozaki, Yuichi Ishikawa
    1988 Volume 52 Issue 12 Pages 1276-1284
    Published: 1988
    Released: April 04, 2008
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    Intergranular corrosion behavior of 13Cr and 17Cr martensitic stainless steels was studied by electrochemical and immersing corrosion tests. Effects of the metallurgical and environmental conditions on the intergranular corrosion of various tempered steels were examined by the following tests and discussed.
    (a) Anodic polarization measurement and electrolytical etching test in 0.5 kmol/m3 H2SO4 solution at 293 K.
    (b) Immersion corrosion test in 0.88 kmol/m3 HNO3 solution at 293 K.
    (c) Long-time immersion test for specimens with a crevice in a high purity water at 473 K∼561 K.
    It was found from the anodic polarization curves in 0.5 kmol/m3 H2SO4 solution at 293 K that the steels tempered at 773∼873 K had susceptibility to intergranular corrosion in the potential region indicating a second current maximum (around −0.1 V. vs. SCE). But the steel became passive in the more noble potential region than the second current peak potential, while in the less noble potential region general corrosion occurred independent of its microstructure. The intergranular corrosion occurred due to the localized dissolution along the pre-austenitic grain boundary and the martensitic lath boundary. It could be explained by the same dissolution model of the chromium depleted zone as proposed for the intergranular corrosion of austenitic and ferritic stainless steels. The intergranular corrosion occurred entirely at the free surface in 0.88 kmol/m3 HNO3 solution, while in the high temperature and high purity water only the entrance of the crevice corroded. It was also suggested that this intergranular corrosion might serve as the initiation site for stress corrosion cracking of the martensitic stainless steel.
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  • Hidekazu Sueyoshi, Toshinori Ohshige, Katsuro Suenaga, Ryohei Tanaka
    1988 Volume 52 Issue 12 Pages 1285-1292
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    In order to develop a new type of free cutting steel, machinability tests have been carried out for a series of hypo-eutectoid graphitic steels composed of ferrite matrices and graphite nodules.
    In the presence of the graphite nodules the frictional coefficient between tool and chip decreased and the shear angle of chip increased. Therefore, the cutting forces decreased with increasing volume fraction of graphite. The lubrication effect of the graphite nodules became remarkable as the mean diameter of the graphite nodule increased and the mean ferrite path between graphite nodules decreased.
    The hypo-eutectoid graphitic steels exhibited an excellent chip-disposability because the curvature of chip is small and the graphite nodules promotes the crack propagation in chip.
    The influence of graphite nodules on the surface roughness was found to be disregarded from a practical point of view.
    It was concluded that the hypo-eutectoid graphitic steel having an appropriate structure of matrices and graphite nodules can be good free cutting structural steel.
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  • Keijiro Nakasa, Masaaki Umezu, Keisuke Kiyose, Toshio Sugioka, Masanor ...
    1988 Volume 52 Issue 12 Pages 1293-1300
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Three-point bending tests were carried out on the Ti-6Al-4V alloy specimens with various microstructures which were cathodically hydrogen-charged in the sulfuric acid solution, and the effect of hydrogen charging time on the bending strength and the deflection at maximum load was investigated.
    The bending strength σb and the deflection at maximum load δmax of the specimens with granular primary α and either granular β or acicular α+β once decreased with increasing hydrogen charging time tc and showed a minimum at tc\doteqdot100 ks, then increased to reach a maximum at tc=150∼200 ks, and decreased again with further increasing tc. The specimens with acicular α+β structure hardly showed such a tendency, i.e. σb or δmax decreased gradually to a constant value with increasing tc. Hydride thickness BH increased monotonically with increasing tc and the BH was larger in the specimens with granular α+β than in those with acicular α+β. The main reason for the appearance of maximum in σb and δmax seemed that the residual compressive stress near specimen surface caused by the expansion of the α phase during its transformation to hydride cancelled out the tensile stress at bending tests.
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  • Eiji Iwamura, Katsuhisa Nagayama, Tosio Suzuki, Takateru Umeda
    1988 Volume 52 Issue 12 Pages 1301-1302
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
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