Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 33 , Issue 6
Showing 1-22 articles out of 22 articles from the selected issue
  • Genjiro Mima, Toshihiro Oka, Takeyoshi Nishi
    1969 Volume 33 Issue 6 Pages 639-645
    Published: 1969
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    During increasing temperature from room temperature up to 500° or 430°C (in a part, up to 550° or 500°C) with a constant heating rate of 2.5°C/min under the constant boundary shear stress of 50 or 100 g/mm2, observations were made on the grain boundary sliding and over-all deformation of aluminum alloy bicrystal specimens with their boundaries aligned at 45 deg. to the tensile axis.
    The main experimental results on the effects of additional elements and their contents on the grain boundary sliding of aluminum alloy bicrystals containing manganese (0.01∼0.372 at%), copper (0.026∼1.70 at%), magnesium (0.056∼1.95 at%), and zinc (0.027∼3.55 at%) to aluminum were as follows:
    By small additions up to about 0.5 at%, the temperature at which grain boundary sliding became observable at an amount of 0.5 μ rose remarkably with the increase in the content of the additional element in Al-Mn, Al-Cu, or Al-Mg alloys. But, in Al-Zn alloy the effect was sluggish. By a large addition of 0.72 or 1.70 at%Cu, the temperature at which grain boundary sliding became observable corresponded with the one at which the second phase (CuAl2) was soluble in Al-Cu alloy under its equiliblium condition.
    But, by a large addition of 0.865 or 1.95 at%Mg and 1.39 or 3.55 at%Zn, the temperatures at which grain boundary sliding became observable fell down to the same temperature as that of 0.20 at%Mg in Al-Mg alloy, and the temperature in Al-Zn alloy was 30°∼50°C lower than that in pure aluminum. This is owing to the grain boundary precipitation of the second phase (Mg2Al3 or nearly Zn) whose melting point is lower than the α phase.
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  • Akira Kondo, Sadao Doi
    1969 Volume 33 Issue 6 Pages 646-650
    Published: 1969
    Released: April 04, 2008
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    In the growth test or the resistance to oxidation test of cast irons in air, there are always phenomena such as oxidation and decarburization. In this paper, using low Ni and Cr cast irons after the abovementioned test, the decarburization coefficient K was obtained. The equation employed is
    (This article is not displayable. Please see full text pdf.)
    When n=3, the expansion of eq. (1) divided by 2C0 leads to
    (This article is not displayable. Please see full text pdf.)
    Here, the above equation may be taken as C⁄2C0=f(K).
    For a variety of radius r, C⁄2C0=f(K) is plotted on a graph where by the values of K are readily read.
    If the radius r changes, the decarburization coefficient K must always remain constant. But, the values of K are more or less variable. Then, the K of the specimen is the mean value of the K which is obtained from eq. (2) at two points on the radius r. The values of K for other specimens are similarly calculated. The results obtained are as follows:
    (1) On heating at 950°C for 60 hr, the decarburization coefficient K of specimens containing Cr is 2.5×10−7∼6.25×10−7(cm2·sec−1). These values of K vary inversely with the Cr content.
    The values of K for specimens containing Ni are 3.18×10−7∼6.25×10−7(cm2·sec−1), varying proportionally with the Ni content.
    (2) On heating at 800°C for 90 hr and 40 hr, the values of K(0.61×10−7∼1.42×10−7(cm2·sec−1) for 90 hr, 0.99×10−7∼1.31×10−7 (cm2·sec−1) for 40 hr) of specimens containing Cr, vary inversely with the Cr content. The effect of Ni additions or K is not so clear, but the value is 1.09×10−7∼1.34×10−7(cm2·sec−1) for in case of the 90 hr heating and 1.06×10−7∼1.34×10−7(cm2·sec−1) in case of the 40 hr heating.
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  • Saburo Nasu, Hiroyuki Yoshida, Yotaro Murakami
    1969 Volume 33 Issue 6 Pages 651-657
    Published: 1969
    Released: April 04, 2008
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    In order to study the effect of small amounts of additional Co elements in Cu-2 wt%Be alloy, the Fe57 Mössbauer effect has been investigated using the specimen in which Co57 was doped. For the various aging sequences in the Cu-Be alloy, Mössbauer absorption spectra were measured at room temperature. All of the spectra obtained at room temperature show the superposition of paramagnetic and ferromagnetic components.
    From the paramagnetic single line, the isomer shift was estimated and it was found that the value did not greatly differ from that of Fe57 in pure Cu. It is concluded that the paramagnetic Co component corresponds to the Co atoms dissolved in the Cu-Be alloy matrix. From the ferromagnetic 6-line components, the effective internal magnetic field of Fe57 dissolved in the ferromagnetic Co component was estimated. The amount of the ferromagnetic Co component was also estimated. From these results, it was found that the ferromagnetic Co component constituted Co-rich particles. And these ferromagnetic particles were also observed by thin foil electron microscopy.
    From the results obtained, the role of Co atoms in the aging characteristics of Cu-2 wt%Be alloy was discussed.
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  • Akira Suzuki, Yutaka Nagaoka
    1969 Volume 33 Issue 6 Pages 658-663
    Published: 1969
    Released: April 04, 2008
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    An experimental study has been carried out to investigate the effect of growth variables on dendrite morphology and dendrite arm spacing in 25Cr-20Ni stainless steel and 1Cr-0.25Mo steel, solidified vertically under semi-steady state conditions.
    The condition for cell formation and the cell to dendrite transition has been determined quantitatively for stainless steel. Dendrite morphology changes from a simple one to complicated cruciform with the increase of growth rate V and the decrease of temperature gradient G. It is shown that there exists the critical values of GV, below which secondary or tertiary dendrite arms are formed. It follows that the formation of dendrite arms in higher order is governed by the same parameter as in case of the cell to dendrite transition.
    Primary dendrite arm spacing is proportional to 1⁄G0.4V0.2, while the size of cellular substructure is proportional to 1⁄GV. Both secondary arm spacing and tertiary one depend upon the cooling rate.
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  • \={O}hiko Kammori, Isamu Taguchi, Akihiro Ono
    1969 Volume 33 Issue 6 Pages 664-668
    Published: 1969
    Released: April 04, 2008
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    Potentiostatic electrolysis methods using 5%Na-citrate-1.2%KBr electrolyte (pH 7, adjusted with citric acid), 5%Na-citrate-1.2%KBr electrolyte (pH 5), 15%Na-citrate-1.2%KBr electrolyte (pH 7), 15%Na-citrate-1.2%KBr electrolyte (pH 5), 15%Na-citrate-1.2%KBr electrolyte (pH 3), 15%Na-citrate-1.2%KBr electrolyte (pH 3, adjusted with hydrochloric acid) and 50%Na-citrate-1.2%KBr electrolyte (pH 7) were compared for quantitative extraction of cementite from low carbon steels.
    The method using 15%Na-citrate-1.2%KBr electrolyte (pH 3, adjusted with citric acid) was recommended, because of the quantitativity of extraction and the least dependence of the extraction ratio upon the electrolytic potential. The recommended electrolytic conditions were discussed with the results of measurements of potential-current curves of the extracted cementite residues.
    The steel sample (50×25×5 mm) is suspended as an anode in about 1.3 L of 15%Na-citrate-1.2%KBr electrolyte adjusted to pH 3 by citric acid. From 0.1 to 1 gram of the sample is potentiostatically electrolyzed at −400 mV vs SCE under nitrogen atmosphere. The residues attached to the sample and those in the anode cell electrolyte are collected through a Millipore filter and then washed by 2% sodium citrate solution. Iron in the residues is determined by Nitroso R Salt spectrophotometry and calculated as cementite.
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  • \={O}hiko Kammori, Isamu Taguchi, Ken-ichi Takimoto
    1969 Volume 33 Issue 6 Pages 669-672
    Published: 1969
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    In order to measure the size distribution of precipitates and inclusions in steels and to analyze them after classification by the sizes, a wet method was developed for sieving under ultrasonic vibration the residues which were chemically extracted from steels. Ultrasonic vibration prevented small particles of the residues from aggregation and accelerated sieving.
    Metallic sieves with openings of from 20 to 2 μ were made by electroplating coarse copper sieves with nickel and platinum. A suitable apparatus to this sieving method was made.
    This method was applied to synthetic chromium carbide and the residues extracted from zirconium steel by the acid dissolution method. The reproducibility of sieving was satisfactory. The analytical results of the sieved residues were also discussed.
    By this method, about 50 mg of the extracted residues can be sieved in about 25 min with 5, 10, 15 and 20 μ sieves.
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  • Takashi Daikoku, Akira Kaneko
    1969 Volume 33 Issue 6 Pages 673-678
    Published: 1969
    Released: April 04, 2008
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    The fundamental investigation on the Tufftride process, which is widely applied in this country, was performed.
    The results obtained are summarized as follows:
    (1) The aeration of the Tufftride bath has to be carried out in order to ensure a good nitriding performance.
    (2) However, there must be an upper limit to the amount of air bubbled through the bath, since an increased aeration also involves an increased consumption of salt bath constituents.
    (3) The nitriding reaction in the Tufftride process can be considerably promoted, if the Tufftride treatment is carried out at temperatures above 530°C.
    (4) The accelerated nitriding reaction can be explained by considering the interface nitrogen concentration which increases linearly as nitriding temperature becomes higher.
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  • Kazuo Kawamura, Toshio Watanabe, Kôichi Nishizaka, Masaaki Onode ...
    1969 Volume 33 Issue 6 Pages 679-685
    Published: 1969
    Released: April 04, 2008
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    Based on the Claisse’s model, the authors introduced a theoretical formula, in consideration of the effects of particle size and mixing rate of particles, for the intensity of fluorescent X-ray for the inhomogeneous system, and the grade of homogeneity was determined. The formula shows that the internal standard (Co) is more effectively used in analysis of Fe when the specimen and other substances to be added are pulverized to the size of under 2∼3 μ and their particles are sufficiently mixed well; insufficient mixing results in an apparent increase of paticle size.
    It was confirmed by the microscopic observation that the iron ore sample could be pulverized to the size of under 5 μ by wet crushing for 3∼5 min with the internal standard and the binder for briquetting, and that the mixing was also achieved sufficiently well by this crushing method. The influence of the matrix was almost completely cancelled by the present method and Fe was determined with good accuracy for the samples with a wide composition range of Fe, such as iron ores, manganese ores and slags. The calibration curve was not necessarily linear over a wide composition range of Fe, probably due to the little differences between the absorption coefficients of Fe and Co.
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  • Hakaru Masumoto, Shôhachi Sawaya
    1969 Volume 33 Issue 6 Pages 685-687
    Published: 1969
    Released: April 04, 2008
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    The thermal expansion and Young’s modulus of the cobalt and palladium alloys have been measured in the temperature range from 0° to 990°C with a dilatometer and by means of a vibrator-controlled oscillator system, respectively, and it has been found that the mean linear thermal expansion coefficient (0°∼40°C) shows maximum value in the α phase alloy containing 90%Pd which has a ferromagnetic Curie point of 150°C and the mean temperature coefficient of Young’s modulus (0°∼40°C) shows a positive value in the concentration range of 90.5∼95%Pd, and its largest positive value is +59.78×10−5 in the alloy containing 94% palladium.
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  • Kaizo Monma, Hajime Suto, Yoshikazu Nakamura
    1969 Volume 33 Issue 6 Pages 687-693
    Published: 1969
    Released: April 04, 2008
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    In order to investigate the tertiary creep of iron and 2 1/4 Cr-1Mo steel, test pieces were tested with a vacuum creep testing machine under constant loads and constant stresses at 600°C. It was observed that the local contraction and surface cracks and/or voids were initiated in the primary stage on the creep curve under a constant stress and that they were accelerated with increasing creep strain. The contributions of the local contraction and cracks on the acceleration of creep of iron were estimated and it was concluded that these effects were almost comparable to each other and that played an important role on the acceleration of creep of iron. However, in the case of 2 1/4 Cr-1Mo steel, it was considered that the most important factor of tertiary creep was grain boundary cracks in the center of the specimen. Therefore, in the observation of a straight line portion on a creep curve of iron and steels, it is premature to conclude that the creep is in progress in the physically steady state in which work hardening and dynamic recovery are balanced against each other.
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  • Hiroshi Miura
    1969 Volume 33 Issue 6 Pages 693-698
    Published: 1969
    Released: April 04, 2008
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    The changes in the microstructure of a hypo-eutectoid carbon steel by thermal cycling below Ac1 was investigated by the point counting method. The maximum heating temperature of thermal cycling was 690°C and the holding time was 240 seconds. In order to find out the characteristic feature of the changes in the microstructure by thermal cycling, the changes in the microstructure by steady (isothermal) heating were compared with those by thermal cycling.
    The lamellar pearlite of the original structure was spherodized and the hardness was decreased by thermal cycling. The finer lamellar pearlite, the quicker this spherodizing process was proceeded. The rate of the spherodization by thermal cycling was more than twice as fast as in the case of steady heating. The characteristic features of spherodization by thermal cycling are as follows. The spherodized pearlite cementite was fine and uniform. The shape of pearlite colony was not changed so much by the spherodization. And the spherodizing process was proceeded very quickly in the colony. It was considered that the rapid spherodization by thermal cycling was due to the decomposition of the pearlite cementite at many positions and the precipitation of the fine spherical cementite in the proeutectoid ferrite by thermal cycling.
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  • Renpei Yoda, Takashi Arai
    1969 Volume 33 Issue 6 Pages 699-705
    Published: 1969
    Released: April 04, 2008
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    Investigation was made on the effect of the working degree on the creep-rupture strength of molybdenum coated with Nickel-base heat-resistant alloy of Nimonic 90 and cobalt-base heat-resistant alloy of S-816 subjected to casting and 25% to 80% hot-working at 1000°C and 1150°C. The creep-rupture strength was improved as the working degree was increased, but it was deteriorated adversely by heavy working such as 80% reduction, due to the lowering of the recrystallization temperature of molybdenum, and this tendency became marked with lowering working temperature. When the working degree is small, the high stress and short-time strength is low but the deterioration of the low stress and long-time strength is small. Molybdenum coated with S-816 alloy has usually a superior short-time strength, but an inferior long-time strength compared with molybdenum coated with Nimonic 90 alloy under the same reduction by working. Molybdenum shows ductile fracture under the high stress and short-time test, but shows brittle fracture through the grain boundary of molybdenum under the low stress and long-time test because of the recrystallization of molybdenum.
    The recrystallization temperature of molybdenum worked at 1000°C is around 1100°C at 80% working and around 1150°C at 65% working, and the strain of molybdenum worked heavily is recovered easily by heating until 1150°C and molybdenum is softened, but the worked properly can be sustained up to a considerably high temperature. Accordingly, for improving the long-time creep-rupture strength of the composite materials, hot workings of 30% to 40% at 1000°C and 40% to 60% at 1150°C are optimal.
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  • Tsuyoshi Masumoto, Yûnoshin Imai, Masaaki Naka
    1969 Volume 33 Issue 6 Pages 705-710
    Published: 1969
    Released: April 04, 2008
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    The isothermal diagrams of the 7%Cr-Fe-C-N system were examined at various temperatures between 1300° and 700°C in the range of compositions up to 0.34% carbon and 0.25% nitrogen. In consideration of the phase relationship, the phase reaction of the 7%Cr-Fe-C-N system was made clear and the sectional diagrams were constructed at fixed contents of 0.05, 0.1 and 0.2% nitrogen. In the Fe-Cr-C-N system, it was assumed that two quaternary peritecto-eutectoid reactions (γ+Cr23C6\ ightleftarrowsα+Cr7C3+Cr2N and γ+Cr2N\ ightleftarrowsα+Cr7C3+CrN) exist at about 780° and 770°C, respectively.
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  • Shôtaro Shimizu, Eigô Hashimoto
    1969 Volume 33 Issue 6 Pages 711-715
    Published: 1969
    Released: April 04, 2008
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    The Platinum-Cobalt alloy with equiatomic composition was disordered by water quenching from 1000°C. After the disordering treatment, the alloy was cold rolled to 15∼80% reductions in thickness and then aged at temperatures between 300° and 750°C.
    Magnetic properties of these specimens were measured for the directions of rolling, width and thickness.
    The results are summarized as follows;
    (1) When the Pt-Co alloy in the disordered state is cold rolled, ordering transformation is promoted through the consequent aging processes. In this case, with increasing degree of cold reduction, the transformation takes place at a lower temperature or in a shorter time.
    (2) The cold rolling preceding the aging processes brings a unfavorable effect on the permanent magnet properties of the alloy, and this effect becomes remarkable as the degree of reduction become severer.
    (3) A sort of magnetic anisotropy is induced in the alloy by the cold rolling preceding the aging processes. Consequently the permanent magnet properties such as Hc, Br and (BH)max, which are obtaind through the aging processes, stand in order of the direction of rolling>width>thickness.
    (4) A uniaxial magnetic anisotropy, which has its easy axis along the rolling direction, is induced by cold rolling of the disordered Pt-Co alloy. The magnitude of the anisotropy is about Lu=−4×105 erg/cc for the specimen of 50% reduction.
    (5) Lu reaches gradually to zero through the initial step of the aging process and then turns its sign to plus as the ordering transformation takes place. At the same time, cubic magnetic anisotropy Lc develops.
    (6) The above-mentioned anisotropy induced by cold rolling can be eliminated by disordering treatment, e.g. water quenching from 1000°C, and the alloy becomes isotropic again.
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  • Hidehiro Gotô, Fujio Maeda
    1969 Volume 33 Issue 6 Pages 716-719
    Published: 1969
    Released: April 04, 2008
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    A method is described for the simultaneous determination of arsenic and tin in iron, steel and iron ore by D. C. and A. C. polarography. Iron and steel is dissolved in perchloric acid and nitric acid, but iron ore is fused with sodium carbonate and a sodium peroxide mixture and then dissolved in nitric acid and perchloric acid. Arsenic and tin are separated from iron and other ions by using the EDTA masking-Be (OH)2 precipitation technique. The precipitate is dissolved with 10 mL of sulfuric acid(1+1), and then arsenic is reduced to As3+ with hydrazine sulfate.
    Arsenic is determined using D. C. polarography (−0.45∼−0.65 V vs. Hg pool) and tin is determined using A. C. polarography (−0.35∼−0.60 V vs. Hg pool) in 0.2 M tetraethylammonium chloride-1.2 N hydrochloric acid-2 M ammonium chloride-1 N sulfuric acid supporting electrolyte.
    The standard deviations (%) for arsenic (0.053%) and tin (0.040%) in steel were 6.36% and 2.08%, respectively.
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  • Harue Wada, Kôki Gunji, Tsuguyasu Wada
    1969 Volume 33 Issue 6 Pages 720-724
    Published: 1969
    Released: April 04, 2008
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    The solubility of nitrogen in liquid V and Fe-V system has been measured in the temperature range from 1800° to 2200°C over wide composition range using the levitationmelting method.
    The solubility of nitrogen in liquid V was very high and decreased with increasing temperature. In the Fe-V system, it was increased with increasing V content and decreased with increasing temperature. The departure of this system from Sieverts’ law deserves attention because the activity coefficient was decreased with increasing nitrogen partial pressure.
    Values of the partial molar heat of solution Δ\barHN of nitrogen and interaction coefficient eN(v) were determined as functions of composition and of temperature, respectively. Δ\barHN in Fe-V system showed a higher negative value than that in the Fe-Cr system. Enthalpy coefficient hN(v) was estimated as −2.26 kcal/mol.
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  • Hisashi Suzuki, Mitsuo Ueki
    1969 Volume 33 Issue 6 Pages 724-729
    Published: 1969
    Released: April 04, 2008
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    Following the previous work, the present study was undertaken for the purpose of obtaining the material having an excellent spring property and high corrosion resistance. Mechanical properties of Cu-20%Ni alloys containing various amounts of Be and Cr respectively, have mainly been investigated. These alloys were cast, hot-worked, solution-treated at various temperatures, cold-worked by 60∼90% to 0.5 mm thickness and subsequently aged at various temperatures for various times.
    The results obtained were as follows:
    (1) The properties in the aged state such as the spring or other mechanical properties of Cu-20%Ni alloys were sharply improved by adding a small amount of Be.
    (2) The alloy containing about 0.4%Be showed a maximum value of about 110 kg/mm2 in Kb, when it was solution-treated at 1050°C, quenched, cold-worked and then aged at 400°∼500°C for 1 hr. The values of Kb obtained for the alloys containing Cr amounted to about 70 kg/mm2 at most.
    (3) It was confirmed that the alloys containing Be and Cr were age-hardened due to the precipitation of NiBe (super lattice) and Cr, respectively. The mechanical properties of the alloys containing Be attained a maximum, when NiBe was in the state of G. P. plus intermediate phases.
    (4) The stress corrosion resistance of both alloys was much superior to that of nickel-silver.
    (5) From the above results, it has been concluded that the commercially available nickel-silver can be replaced by the alloys containing a small amount of Be.
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  • Masanobu Ohmori, Yoshitoyo Yoshinaga, Takeshi Kawahata
    1969 Volume 33 Issue 6 Pages 730-736
    Published: 1969
    Released: April 04, 2008
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    At four temperatures, i.e., −78°C, room temperature, 100° and 200°C, a killed carbon steel with 0.14%C was pulled over a strain rate range of ∼2.8×10−6 l/sec. The strain rate dependence of the strength was examined here from a viewpoint of dynamic strain ageing. The results obtained are summarized as follows:
    (1) Around a temperature at which the occurrence of dynamic strain ageing begins, the yield stress (lower) remains nearly constant when pulled at a given strain rate.
    (2) The activation energy for the dynamic strain ageing obtained from a relation between the temperature of onset of the ageing and the strain rate agrees fairly well with that for the diffusion of C or N atoms in α-iron. On the other hand, the energy for the ageing obtained from another relation between the temperature, at which the deformation stress showed its peak, and the strain rate was found to be 1.5∼2.0 times larger than that for diffusion of the above interstitials.
    (3) At −78°C, the yield and flow stress were never affected by the dynamic strain ageing. And a linear log-log relation between the yield stress and the strain rate and another linear one between the flow stress and the rate are plotted.
    (4) The observed phenomenon that the yield stress and the tensile strength at room temperature become almost independent of the strain rate around the rate of 10−6 l/sec results from the dynamic strain ageing. The small strain rate sensitivity of the yield stress between the rates of 10−1 and 10−4 l/sec cannot be explained quantitatively in terms of the dragging stress from the Snoek ordering of C atoms.
    (5) Negative strain rate dependences of the yield stress and the tensile strength observed at 100° and 200°C are caused by the dynamic strain ageing.
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  • Tohei Ototani, Yasuzi Kataura
    1969 Volume 33 Issue 6 Pages 736-741
    Published: 1969
    Released: April 04, 2008
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    The effects of degree of cold reduction, annealing temperature, heating rate and thermal treatment prior to cold work on the recrystallization in cold rolled low carbon rimmed, and aluminium calcium deoxidized sheet steels were investigated. The recrystallization characteristics of aluminium calcium deoxidized steels differed from those of the rimmed steel; the recrystallization times of the former were considerably longer and elongated pancake grain structures were formed compared with the equiaxed ones of the annealed rimmed steels. The amount of grain elongation of the aluminium calcium deoxidized steel was more than that of the aluminium deoxidized steel. The formation of elongated grain structures appeared to be due to aluminium nitride which was solution treated at 1200°C before hot rolling and then precipitated on the grain boundaries or subboundaries during the final annealing process after cold reduction of the aluminium deoxidized and aluminium calcium deoxidized steels. The mechanism of formation of the elongated grain structures was considered in terms of the influence of aluminium nitride precipitation during recrystallization.
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  • Tohei Ototani, Yasuzi Kataura
    1969 Volume 33 Issue 6 Pages 742-746
    Published: 1969
    Released: April 04, 2008
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    By means of a low frequency internal friction method the combined effect of nitrogen and aluminium of the cold rolled rimmed steel, aluminium and calcium deoxidized steels has been studied during isothermal or isochronal annealing. For these materials which formed typically elongated pancake grains as shown in a previous report, the lowering of nitrogen in solution during the recovery to the early stage of recrystallization was attributed to fine precipitation of aluminium and nitrogen on the grain boundaries or subboundaries of the matrix. It has been assumed that the aluminium calcium deoxidized steel possesses the superior characteristics of a stabilized steel, because the solubility of carbon and nitrogen in α iron of the aluminium calcium deoxidized steel was considerably low compared with that of aluminium deoxidized steel.
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  • Toshio Katagiri
    1969 Volume 33 Issue 6 Pages 746-749
    Published: 1969
    Released: April 04, 2008
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    The purpose of this study is to investigate the reaction in gas boronizing of iron with BCl3 and H2. By microscopic examination of gas boronized iron and infrared spectroscopic analysis of the gaseous products during the boronizing reaction, it was observed that the formation of dichloroborane by hydrogenation of BCl3 according to the reaction
    (This article is not displayable. Please see full text pdf.)
    was required to form the needle shape boride layer consisting of two layers on the surface of the iron.
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  • Yasuko Kondo, Ryukichi Nagasaki, Tadao Sano
    1969 Volume 33 Issue 6 Pages 750-754
    Published: 1969
    Released: April 04, 2008
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    0.4 wt%Ca-Be alloy was oxidized in moist CO2 (water vapour pressure, 14 to 25 mmHg) over the temperature range 700°∼800°C. Discontinuity of the weight gain vs. time curves suggests that the oxidation of 0.4 wt%Ca-Be alloy occurs through three reaction stages. The rates of oxidation at the initial two reaction stages were parabolic.
    The effect of water vapour pressure on the parabolic rate constants as
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    where kp is the parabolic rate constant, kp° the parabolic rate constant in dry CO2, a constant, ΔH the activation energy for the parabolic oxidation.
    Pressure of moisture effected the activation energy of the reaction suggesting that the rate controlling step is different from that for dry CO2. Increase in the partial pressure of water vapour causes a change in the entropy term in a manner indicated in the above equation.
    The third stage follows a linear rate law resulting in a rapid disintegration.
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