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Volume 41, Issue 5
Displaying 1-17 of 17 articles from this issue
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Hiroshi G. Katayama1977 Volume 41 Issue 5 Pages 427-431
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSynthetic MgCr2O4 was reduced isothermally and non-isothermally with graphite powder in a gaseous flow of 300 cc/min and a nonflow of Ar. The reduction rate was measured by means of a thermobalance using the silica glass spring.
The results are as follows:
(1) The reduction took place in three orderly steps, i.e., in periods of incubation, acceleration and retardation.
(2) The incubation period was shortened with rising reduction temperature. At the same temperature, the period in the gaseous flow of 300 cc/min was longer than in the nonflow of Ar.
(3) In the acceleration period, the apparent activation energy was found to be about 72 kcal/mol. This value was nearly equal to those for the reaction C+CO2=2CO, so it seemed that the reaction in the period was controlled by the Boudouard reaction.
(4) The reduction in the gaseous flow of 300 cc/min retarded earlier than in the nonflow of Ar because the total pressure (PCO+PCO2) was decreased by flowing Ar.
(5) Chromium carbides produced by the reduction in the gaseous flow of 300 cc/min were both Cr3C2 and Cr7C3, while in the nonflow of Ar only Cr3C2 was produced.View full abstractDownload PDF (406K) -
Hisashi Suzuki, Koji Hayashi, Tsutomu Yamamoto1977 Volume 41 Issue 5 Pages 432-437
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe transverse-rupture strength (σm) of TiC-Mo2C-TiN-Co alloy (Co alloy) was studied at room temperature paying attention to microstructural defects which act as fracture sources, and the result was compared with that of TiC-Mo2C-TiN-Ni alloy (Ni alloy). (1) It was confirmed that the strength (σ0) of the alloy having none of defects was higher in the Co alloy than in the Ni alloy. However, in reference to σm for conventional alloys, σm was generally lower in the Co alloy. The reason for this discrepancy was made clear if one considered the linear relation between σd−1 and \sqrta in both alloys (σd, external stress on the defect at the moment of fracture; 2a, defect dimension), and the results on the dimension, location or nature of the defects, which varied with the sort of binder, TiN and binder contents. (2) The comparatively high σ0 and high hardness for the Co alloy were considered to be caused by the strain-induced transformation of its binder phase. (3) Thus, the Co alloy would be very promising, within the scope of this experiment, if the dimension of the large defects which are usually observed could be decreased to a very small value of less than about 10∼15μ.View full abstractDownload PDF (802K) -
Tohru Arai, Hironori Fujita, Noboru Komatsu1977 Volume 41 Issue 5 Pages 438-444
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSWhen steels containing carbon were treated at 850∼1050°C in a fused borax bath containing both Fe-V and Fe-Nb powders, complex carbide V-Nb-C layers were formed on the steel surface.
Effects of the treating condition on the distribution of V and Nb in the layer and the growth rate were investigated.
The results obtained are summarized as follows.
(1) The layer formed on SK 4 specimen had higher Nb/V ratio than that in the bath. The V content in the layer was higher near the substrate.
(2) The V content near the substrate increased with the treating temperature, but was not affected by the treating time.
(3) The V content near the surface tented to decrease with the treating temperature and time.
(4) The rate and activation energy for the growth of the complex carbide layer are almost identical with those of VC and NbC carbide layers.
(5) The V content in the complex carbide layer was high in the initial stage but decreased with the treating time.View full abstractDownload PDF (738K) -
Fumio Morimune, Hideo Shingu, Kojiro Kobayashi, Ryohei Ozaki1977 Volume 41 Issue 5 Pages 444-450
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to obtain the information on the grain refinement of Al cast grain, the liquidus surface of the Al-Ti-B system at the aluminum corner was investigated by a chemical composition analysis of the supernatant solutions and by the composition and structure analysis of the sediments seperated in Al-Ti-B melts by the gravity segregation.
The results are summarized as follows.
(1) Both the liquidus curve and the peritectic-limit of TiAl3 are little affected by the addition of boron to the Al-Ti system.
(2) Based on the result of the micro analysis using IMA, it is concluded that boron is excluded into the liquid phase on the formation of the TiAl3 phase. It can therefore be concluded that the liquidus surface of the TiAl3 phase constitutes an eutectic line with that of TiB2 phase.
(3) The solubility product of the TiB2 phase matches closely with those reported in the literature for the range of Ti:B ratio higher than that of the TiB2 phase.
(4) Based on the assumption that the distribution coefficients of titanium and boron in aluminum are not different from those for the binary alloy, a simple calculation shows that the intersection line of Al and TiB2 liquidus surfaces forms the peritectic reaction.
(5) The Ti:B ratio of TiB2 particles in aluminum-base alloys is about 2.07 by weight and is smaller than the stoichiometric ratio (=2.22). These particles contain several weight per cent of aluminum.
(6) Accordng to the present information about the phase diagram, Al cast grains seem to nucleate directly on the TiB2 particles in the composition range determined by the following unequality: 0<total Ti content −2.07×total B content<0.15 (wt%).View full abstractDownload PDF (832K) -
Kazuo Furukawa, Hideo Ohno1977 Volume 41 Issue 5 Pages 450-457
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt was verified that in the complex ionic liquids of type AX-BX2 such as alkali-fluoroberyllates or alkaliearth-silicates the corresponding-state principle is valid quantitatively under the following conditions: [A] between the following pairs, (i) LiF-BeF2 and MgO-SiO2, (ii) NaF-BeF2 and CaO-SiO2 and (iii) KF-BeF2 and BaO-SiO2, [B] in the composition region between 30 and 70 mol% in AX components, and [C] under the reduced absolute temperature scale with the factors 2.85 in the system (i), or 2.80 in the systems (ii) and (iii). Using the existing experimental data the following physical properties were confirmed to have the same values within experimental error in the corresponding states of both molten materials: (1) ionic packing density, (2) viscosity coefficient, and (3) equivalent conductivity. The liquid structure of both materials is also essentially the same in the corresponding state. Experimental work on molten fluoroberyllates is much easier than that on molten silicates due to the former’s lower melting points and applicability of a Ni-alloy (Hastelloy-N) container. The improvement of scientific understanding of molten fluoro-beryllates will ultimately contribute to the development of science and technology concerning not only molten fluoro-beryllates but also molten silicates.View full abstractDownload PDF (629K) -
Hajime Suto, Kazuaki Sato1977 Volume 41 Issue 5 Pages 458-463
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEffects of tensile stress on the intergranular segregation of phosphorous and sulfur in the tempering of low carbon steels containing 1.7%Cr and 2.5%Cr were investigated by means of Auger electron emission spectroscopy.
The intergranular segregation of phosphorous was found to be enhanced by tensile loading. However, the concentration of sulfur at grain boundaries in steels containing phophorous was decreased by loading. These results were interpreted in terms of the boundary structure which was suggested from the thickness of those segregation zones, that is, phosphorous atoms are adsorbed and sulfur atoms precipitate as sulphide at boundaries.View full abstractDownload PDF (476K) -
Bakk Chang, Satoru Yamamoto, Yutaka Kawano, Ryohei Ozaki1977 Volume 41 Issue 5 Pages 464-471
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe present investigation is concerned with nodularization of graphite by the addition of elements such as Ce, Y, La, Ti and Zr, all of which have the distinctive feature to absorb a very large amount of hydrogen at room temperature and to liberate it when the temperature is raised.
The results in the present work are summarized as follows:
(1) The degree of nodularization depended mainly on absorbed hydrogen contents in Ce, Y, La, Ti and Zr.
(2) When Ce, Y and La containing a large amount of hydrogen are immersed into molten metal, fine bubbles of hydrogen about 10 μ in size are evolved.
(3) The addition of so-called sub versive elements like Ti and Zr which have absorbed a large amount of hydrogen also leads to the formation of nodular graphite.
(4) The nodularization of graphite by the addition of Ce, Y, La, Ti or Zr may be due mainly to the precipitation of carbon atoms into the bubbles of hydrogen, whereas these elements themselves have no nodularizing effect or rather have denodularizing effect.
The results in the present work were compared with those by other investigators and it was clarified that these could be explained most reasonably based upon the gas-bubble theory among current hypotheses for graphite nodularization.View full abstractDownload PDF (1105K) -
Bakk Chang, Satoru Yamamoto, Yutaka Kawano, Ryohei Ozaki1977 Volume 41 Issue 5 Pages 471-478
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSome investigations were carried out to clarify the effect of cerium on the nodularization of graphite.
The results obtained in the present works were summarized as follows:
(1) The so-called fading phenomenon was observed in the formation of nodular graphite in the cerium-treated cast irons. This process has the following characteristics.
(i)\phantomii The fading rate in the cerium-treated cast irons is much lower than that in the magnesium-treated ones.
(ii)\phantomi The fading rate hardly depends upon the external pressure or the melting atmosphere (in the vacuum melting or the melting under He gas).
(iii) The fading phenomenon appears with the decrease of the residual cerium contents and occurs with holding time even in the melts containing a constant residual cerium content.
(iv) The fading rate is higher as the melting temperature is raised.
(2) Whether cerium is concentrated in the nodular graphite or not depends on the conditions of its formation.
(i)\phantomii Cerium was often concentrated in the internal nodules of the duplex nodular graphites in the relatively high-cerium specimens. In those which do not have an internal core or even in the internal nodules of the duplex nodular graphites in the low-cerium specimens, cerium was hardly found.
(ii)\phantomi It was extremely rare that cerium was concentrated only towards the center of nodular graphites.
(iii) Cerium was highly concentrated in the net-like structures of the high-cerium (0.20 wt%) specimens.
It was clarified that these results in the present works could not be explained by other theories except gas-bubble theory.View full abstractDownload PDF (925K) -
Bakk Chang, Satoru Yamamoto, Yutaka Kawano, Ryohei Ozaki1977 Volume 41 Issue 5 Pages 479-486
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn the present work, several attemps were made to explain the effect of nodularizing of magnesium being used most widely and to confirm the ability of sulphur to nodularize graphite, which has been regarded as a most deterious element.
The following facts were clarified from the experimental results.
(1) Nodular graphites are formed only by the addition of sulphur, which may result from the precipitation of graphite into sulphur gas bubbles.
(2) The noticeable pressure-dependence of nodular graphite formation is observed in the magnesium-treated cast iron; no nodular graphites are formed in cast iron treated with magnesium under an argon pressure much higher than its equilibrium vapour pressure, despite its sufficient magnesium contents. Nodular graphites are again observed to be formed with decreasing argon pressure.
This indicates that magnesium gas bubbles alone are responsible for the nodularizing of graphite.
These experimental findings support the gas-bubble theory for the formation of nodular graphite.View full abstractDownload PDF (958K) -
Mitsuji Hirohashi, Eiichiro Kawai, Kensuke Mutsuzaki, Matsuo Miyagawa1977 Volume 41 Issue 5 Pages 487-492
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effects of the addition of 0.5%Cu and 0.01%Mg into the superplastic Zn-22%Al alloy (SPZ·CM) on the mechanical properties and the deformation behaviour were investigated.
The results obtained were as follows:
(1) The temperature of the nose of TTT diagram for the SPZ·CM was atout 50°C higher than that of the binary eutectoid alloy (SPZ), but the starting time of transformation was nearly equal. The dissolution into two phases at room temperature started 20 min after solution treatment and water quenching and lasted about 2 hr. The aging phenomenon that grains grew with aging time after the dissolution was found similarly in the case of SPZ.
(2) This alloy was hardened and strengthened with aging time at room temperature, and this alloy did not show softening as in the case of SPZ.
(3) Superplastic elongation more than 200% for the SPZ·CM was obtained above 200°C, but such a large elongation was not observed at room temperature independently of the change of microstructure or grain size.
(4) Cu and Mg added were mainly dissolved in the β-phase and the β-phase was strengthened. The β-phase was precipitated continuously at the boundary of the mother phase called α′. Therefore, the strength of SPZ·CM was larger than SPZ.
(5) The α′-boundary was destroyed by the instantaneous cold-rolling after the solution treatment. The precipitation of the β-phase was dis-continuous so that the flow stress was reduced and the ductility was improved.View full abstractDownload PDF (646K) -
Haruno Okochi, Katsuyuki Takahashi, Shunichi Suzuki, Koichi Sato, Emik ...1977 Volume 41 Issue 5 Pages 492-498
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSWhen adequate standard samples are unable to be obtained in the analysis of high alloy steels, or when there are not enough amounts of sample, the electrolytic iron dilution method will be useful. This technique have been developed.
This method was further applied to nickel-base superalloys and these samples could be analysed by using iron and steel standard samples.
High speed steels, stainless steels, heat resisting superalloys, Ni-Co-Cr-Mo steel, Ni-Mo steel and nickel-base superalloys were analysed.
Dilution rates were examined from (1:3) to (1:100) using high speed steel (JSS 609) and nickel-base superalloy. By usual emission spectral analysis some elements (Ni, Cr, Mo and Co) showed good correlation between dilution rates and analytical values but certain elements (Mo, V, Nb and W) gave low analytical values at higher dilution rates. On the other hand, X-ray fluorescence analysis showed good results.
In order to investigate the cause of this phenomenon, the effect of interference lines during emission spectroscopy was examined using binary iron alloy standard samples. Consequently, in the case of standard samples containing small amounts of elements in question, the analytical lines are considerably affected by the interference lines in comparison with the samples diluted with iron.
Then, the method of treating data was decided as follows. Calibration curves are made using the values corrected for the effect of interference lines instead of the standard values and the analytical values are also corrected for the effect of other elements. By this procedure, the electrolytic iron dilution method may be applied to any samples, but titanium cannot be determined.
Nickel-base superalloy was remelted following the usual method and carbon, aluminum, niobium, zirconium and titanium were analysed using nickel-base standard samples.View full abstractDownload PDF (639K) -
Tadashi Momono, Katsuya Ikawa1977 Volume 41 Issue 5 Pages 498-504
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe composite-to-dendrite transitions in the Cd-CuCd3 and Pb-Zn systems near the eutectic composition have been studied under controlled growth conditions at steep temperature gradient and low growth rate.
Aligned structures were obtained over a wide range of hypo-eutectic compositions and showed good agreement with the simple constitutional supercooling criterion proposed by Mollard and Flemings. However, in hyper-eutectic alloys, aligned structures were found to be more stable than predicted by this criterion. The above results show that at high growth rate, the faceted dendrites cannot grow faster than the eutectic interface, resulting in the appearance of the aligned structure only.
The λ∝R−1⁄2 relationship remained valid even for off-eutectic alloys, and λ2R had a tendency to decrease with increasing solute content. By using the equation derived by Jackson and Hunt, the values of interphase boundary energy were roughly estimated to be 23∼58 erg/cm2 for Cd-CuCd3 interphase and 17∼43 erg/cm2 for the Pb-Zn interphase.View full abstractDownload PDF (952K) -
Kazunari Enoki, Satoru Hagiwara, Hiroyuki Kaneko, Yasutoshi Saito1977 Volume 41 Issue 5 Pages 505-510
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe galvanic cell technique involving the stabilized zirconia solid electrolyte was applied to studying the oxidation of cobalt. The cell was the stacked pellet type and was operated in argon and in air. The results obtained were as follows:
(1) The equilibrium values of electromotive force (emf) were measured in argon for the cell: Pt, Co-CoO or CoO-Co3O4|ZrO2(+CaO)|Ni-NiO, Pt. The standard free energies of formation of CoO and Co3O4 were represented by the equations
(This article is not displayable. Please see full text pdf.)
(2) The emf’s of the cell: Pt, CoO or Co3O4|ZrO2(+CaO)|air, Pt were measured in air on heating and cooling at a constant rate. The emf’s changed with temperature corresponding to the formation of CoO and Co3O4 on the thermogravimetric curves.
(3) The changes of emf with time were measured in air at various temperatures for the cell: Pt, Co|ZrO2(+CaO)|air, Pt. At temperatures below 900°C, it was confirmed that CoO and Co3O4 were successively formed on Co. At temperatures above 900°C, CoO was only the oxide formed on Co. The emf decay curves after the cathodic polarization of the oxidized sample indicated that the oxidation process seemed to be more complicated. Further, it was found that the emf oscillated after Co was completely consumed at the metal-electrolyte interface.View full abstractDownload PDF (599K) -
Masateru Suwa, Katsuhiro Komuro, Kô Soeno1977 Volume 41 Issue 5 Pages 511-517
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEffects of graphite content on the wear and the mechanical properties of Cu-Sn casting alloys have been investigated. The volume per cent of graphite varied from 2.5 to 20%. Sound ingots having uniform dispersion of graphite particles were obtained by adding copper-coated graphite particles into the melts containing about 1 at.% of Ti. Casting of the ingots was carried out under a high pressure of about 630 kg/cm2. Two series of graphite-dispersed Cu-8%Sn and Cu-5%Sn-5%Zn-4%Pb alloys containing 0.8%Ti have been used for the investigation of mechanical properties and wear resistance.
Strength and elongation of the alloys decrease with increasing graphite content. However, no difficulty is found for industrial use even in the mechanical properties of the alloys containing 20 vol.% graphite.
Under dry friction, the wear resistance of the alloys is increased with increasing graphite content. The wear rate of the Cu-5Sn-5Zn-4Pb alloys containing 20 vol.% graphite is about 10−9 mm3/mm·kg, which is nearly equal to that of ordinary bronze casting under oil-lubricated friction. However, under oil lubricated friction, a maximum wear resistance is found in the alloys containing about 5 vol.% graphite, and the wear resistance of the alloys containing graphite more than 5 vol.% is decreased.View full abstractDownload PDF (1452K) -
Yutaka Shinata, Yasutoshi Saito, Tsuneo Homma1977 Volume 41 Issue 5 Pages 517-523
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe optically stimulated exoelectron emission from polycrystalline aluminum was measured under the tensile deformation and fracture at room temperature using a picoammeter. The specimen surface at various degrees of deformation was examined by means of metallographic techniques.
During the tensile deformation, the exoelectron emission (EE) occurred at about 3∼4% strain (as-annealed 99.99% Al), and increased monotonously until the maximum load. Then EE decreased slightly in air, and increased abruptly in vacuum. The primary source of EE was attributed to a fresh surface produced by the slip band formation during the tensile deformation, and to the fractured surface after the failure. The EE activity of the slip band was different from that of the fractured surface.
The intensity of EE became weak by shielding the short wave length of the ultraviolet light using a filter, whereas the relative change of the intensity was the same with and without a filter. EE in the present experiment was assumed to be a part of photoelectron emission. As the ultraviolet light irradiation was interrupted after the failure, EE increased depending on the cut-off time in air. This phenomenon was not observed in vacuum.View full abstractDownload PDF (630K) -
Tsuneo Homma, Yutaka Shinata, Yasutoshi Saito1977 Volume 41 Issue 5 Pages 523-527
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe optically stimulated exoelectron emission from the annealed pure polycrystalline aluminum was continuously measured in air at room temperature during the fatigue process under the reversed bending stress using a picoammeter. The surface of the fatigued specimen at various stages was examined by means of metallographic techniques and scanning electron microscopy.
The exoelectron emission (EE) increased with the number of fatigue cycles during the early stages, and then reached a peak at about 10∼20% of the fatigue life. Increase of EE corresponded to the exposure of the fresh surface produced by persistent slip bands. EE showed a peak when the rate of EE decay exceeded that of the fresh surface formation. An incipient crack was observed immediately after the peak, where the marked surface damage was saturated. Since the relative peak position normalized to the fatigue life was almost the same independent of the applied stress, the fatigue failure was predicted at about 10∼20% of the life by measuring EE.
This method might have a possibility of applying to other pure metals and alloys.View full abstractDownload PDF (653K) -
Hidehiko Kamide, Hideo Sugawara1977 Volume 41 Issue 5 Pages 528-534
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCorrosion behavior of 18-8 stainless steel in H2SO4-NaCl solution was investigated in order to clarify the relation between martensites formed during deformation (strain induced martensites: ε and α′) and stress corrosion cracking (S.C.C).
The α′-martensite, which is easily identified by microscopic observation, is formed by subzero-treatment. This martensite has the same crystal structure as that the crystal structure of martensite induced by deformation at room temperature. The subzero treatment at −196°C gave size to wide corrosion grooves on the specimen surface in the SCC and immersion tests in 5 N H2SO4-0.4 M NaCl solution at −325 mV. The morphology of the grooves was in good agreement with the pattern of martensites formed in austenitic matrix.
Transmission electron microscopic obsevation of thin-foil specimens revealed that corrosion grooves and microstriations were formed at α′ and ε-martensite formed by the subzero-treatment, and that micropits and microstriations grew near the strain induced martensite. These phenomena became to appear more distinctly with increasing degree of prestraining and decreasing subzero-temperature.
The above results suggest that the martensites formed locally in the austenitic matrix during deformation at the temperature below the Md point are responsible for the initiation of micropits or microstriations and their propagation, resulting in S.C.C.View full abstractDownload PDF (1258K)
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