Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 42, Issue 11
Displaying 1-17 of 17 articles from this issue
  • Riei Ichikawa, Kenji Miwa
    1978 Volume 42 Issue 11 Pages 1023-1028
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    The apparent viscosity was measured as the value of torque by stirring continuously by a rotor from the molten state to the desired temperatures partial solidified at constant cooling rate in Al-Cu alloys.
    By the stirring, primary α solid particles or dendrites were broken to a mushy state and the structure was observed by water quenching from the stirring temperature.
    The results obtained were as follows.
    (1) With increasing Cu concentration, the increase in the value of torque shifted to lower temperatures below the liquidus line and became retarded.
    (2) With increasing Cu concentration, the value of torque showed increase at a small volume fraction of the solid phase.
    (3) As the solid particles became finer with increase in Cu concentration, the value of torque showed a marked increase against the volume fraction solid.
    (4) Regardless of the Cu concentration, solid particles became finer and spherical with the progress of stirring.
    (5) Solid particles in the mushy state were not only crushed but also aggregated by mechanical stirring.
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  • Jin Onuki, Masateru Suwa, Kô Soeno
    1978 Volume 42 Issue 11 Pages 1029-1034
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    In the construction of diodes, n-type surfaces of Si wafers are frequently brazed to metal contact discs (W or Mo) by using Al solder. After brazing, the diodes exhibit the foward voltage drop (FVD) because of the p-type regrowth layer formed on the n-type Si from the melt. It is considered that the modification of primary Si in a hyper-eutectic Al-Si alloy is effective in preventing the growth of regrowth layer. From this point of view, effects of thickness of Al, brazing temperature, holding time, cooling rate and P concentration in n-type Si on the regrowth layer have been investigated by microscopy. The following conclusions have been obtained.
    (1) FVD in the diodes decreases with an increment of the discontinuity ratio of the regrowth layer.
    (2) It is found that the modification in the hyper-eutectic Al-Si alloy and the prevention of growth of the regrowth layer on n-type Si have a close connection with each other. In the case of the Al-Si layer thinner than 4 μm, it is possible to get a large discontinuity ratio.
    (3) Even if Al is thick (i.e. 15 μm), it is also possible to get a large discontintinuity ratio by using n-type Si containing about 1∼1.4 at%P.
    (4) It is also found that the growth of the regrowth layer is affected greatly by the shape of the solid-liquid interface.
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  • Masateru Suwa, Katsuhiro Komuro, Kô Soeno
    1978 Volume 42 Issue 11 Pages 1034-1038
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    The effect of graphite particle size on the wear of graphite-dispersed bronze castings has been investigated. Sound ingots having uniform dispersion of graphite particles were obtained by adding copper-coated graphite particles to the melts containing about 1 at%Ti. Casting of ingots was carried out by pressure crystallization casting under a high pressure of about 62 MPa. Cu-5Sn-5Zn-4Pb-0.8Ti and Cu-5Sn-5Zn-4Pb-0.8Ti-0.5P alloys containing 6% graphite (about 20 vol%) have been used for the investigation of wear resistance. The graphite particle size varied from 8 to 100 mesh.
    The results obtained are summerized as follows: (1) It is found that the wear resistance tends to increase as the graphite size is coarser. It is considered that the tendency depends on the following phenomenon. The graphite tends to be covered easily by a plastic flow layer as the graphite is finer, and consequently lubrication by graphite does not continue. (2) When phosphorus is added to the alloys, the graphite size dependence against sliding wear is decreased and wear resistance is increased. (3) The alloys containing pulverized graphite powder have high wear resistance as compared with granulated graphite powder.
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  • Keiji Hara, Hideo Yoshinaga, Shotaro Morozumi
    1978 Volume 42 Issue 11 Pages 1039-1047
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    High-temperature mechanical properties of titanium carbide were investigated by compression at high temperatures from 1073 K to 2273 K, using single crystals, radiofrequency-melted polycrystals, arc-melted polycrystals and sintered materials.
    The brittle to ductile transition temperature of TiC0.88 single crystals is about 1150 K and they show almost unlimited ductility above about 1450 K. Their active slip plane is {1\bar11} in a wide orientation range of specimens, but it becomes {100} when compressed along the ⟨111⟩ direction. The critical resolved shear stress evaluated by assuming the slip direction to be ⟨011⟩ is about 2 times higher for {100} slip than for {1\bar11} slip. The yield stress of these materials decreases exponentially with temperature. The stress in the investigated temperature range is higher in the order of sintered, arc-melted, radio frequency-melted and single crystals, and the transition temperature is higher in this order as well.
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  • Moriyasu Tokiwai, Shotaro Morozumi
    1978 Volume 42 Issue 11 Pages 1047-1053
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    An internally oxidized V-2 wt%Zr alloy, together with an un-oxidized alloy of the same composition and pure vanadium, irradiated to 7×1020 neutrons/cm2 (En>1 MeV) at about 513 K and then annealed for 3.6×103 s (1 h) at various temperatures up to 973 K, was tensile-tested at room temperature. The tensile properties were considered, referring to the change of electrical resistivity in cumulative isochronal annealing of the irradiated alloys. Electron micrographs of the internally oxidized alloy, irradiated to 1.2×1021 neutrons/cm2 at about 673 K and subsequently annealed, were also referred. The results obtained are as follows:
    (1) The strength versus annealing temperature curve for the internally oxidized alloy showed two peaks, the larger one at 573 K and the smaller one at 723 K, which were thought to result from an interaction between radiation-induced defects and interstitial impurities, especially oxygen dissolved in the alloy by the internal oxidation process. The un-oxidized alloy did not show any hardening peaks on the curve, because of the scavenging effect of zirconium as reported for titanium in the previous work.
    (2) Correspondingly, a large decrease of electrical resistivity, measured at 77 K, was observed in the internally oxidized alloy annealed at about 510 K, while a decrease in electrical resistivity was observed at about 740 K in the un-oxidized alloy. Part of the latter decrease might be attributed to the internal oxidation of zirconium in the alloy during annealing.
    (3) Electron microscope observation revealed that many dislocations, tangling around dispersed particles, and defect clusters were produced by the irradiation in the internally oxidized alloy.
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  • Hirobumi Okabe, Hideo Ike
    1978 Volume 42 Issue 11 Pages 1053-1060
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    A study has been made on the isothermal oxidation behaviour of Fe-14Cr-Al alloys containing up to 2.0%Al in 1 atm O2/H2O vapour mixtures in the temperature range 900 to 1200°C. Compared with the previously reported behaviour in dry O2, little change has been observed on 0.3%Al alloy at and below 1100°C. The good oxidation resistance of the alloy is explained to be due mainly to the stability against moisture of the scale rich in Cr2O3, the nucleation and growth of which being brought about preferentially by an internal oxidation zone of dispersed α-Al2O3 particles. At 1200°C water vapour begins to have effects on the alloy in such a way that it accelerates the initiation and growth of warts formed exclusively along the specimen edges. The structure of warts formed on the alloy after breakaway is double-layered and has been characterized by accumulation of Al just beneath the outermost part of the inner layer. This accumulation of Al has been considered to be the result of agglomeration of the dispersed α-Al2O3 particles during the growth of the warts. Two types of breakaway are found to occur in 0.1 and 0.8%Al alloys. One appears predominantly along the specimen edges at high temperatures, with the Al accumulation as in the case of 0.3%Al alloy, and the other, with no significant accumulation of Al, occurs uniformly on the specimen surface at relatively low temperatures and a high level of water vapour contents. Under the oxidizing condition where the latter type of breakaway occurs, development of the internal oxidation zone of well-developed and dispersed α-Al2O3 particles is not sufficient in these two alloys so that the preferential formation of the Cr2O3-rich scale cannot be fully established. The alloys are thus subject to an intense effect of moisture as observed. The oxidation resistance of 2.0%Al alloy is high at temperatures below 1000°C, beyond which it decreases more rapidly than in dry O2.
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  • Naotake Niwa
    1978 Volume 42 Issue 11 Pages 1060-1066
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    The process of “cup and cone” fracture was examined in commercial pure titanium plate pulled in uniaxial tension. Direct and continuous observation of the fracture process was possible because the fracture process of titanium plate used in this experiment was completed almost in two-dimensional state like plane strain state.
    The fracture process is summarized as follows: the formation of shear bands which intersect in the center of the necked portion of a specimen occurs prior to the onset of fracture. These macroscopic shear bands are composed of a number of highly localized fine bands of intense shear deformation in layers and along the direction of the macroscopic shear bands.
    After the formation of these intersecting macroscopic shear bands, the number and size of voids increase extraordinarily in the rhombus region where the shear bands intersected. Voids grow on the spots where the highly localized fine bands of intense shear deformation intersect and coalesce, resulting in the formation of a few small cracks. This is the onset of fracture.
    Connecting these small cracks, a central crack is formed. It propagates in zig-zag steps producing void sheets within the highly localized fine bands of intense shear deformation. The fracture is completed by separating void sheets having reached the edges of a specimen.
    The formation of intersecting macroscopic shear bands is a critical stage leading to the onset of fracture and intersecting shear bands also play a predominant role in the fracture process.
    Comparing the fracture process of the titanium plate with those of the copper round bar specimens in the previous papers, it is concluded that the above results may be applied to the ductile fracture of round bar specimens.
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  • Mizuo Edamura, Minoru Makimura, Takashi Kajikawa, K\={o}ichi Imai, Sat ...
    1978 Volume 42 Issue 11 Pages 1066-1070
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    The depth of the diffusion zone and the thickness of the compound layer of the ion-softnitrided S15C steel were investigated by optical microscopy by varying the nitriding temperature (450∼600°C) and time (0.25∼30 h).
    \ oindentThe main results were as follows.
    (1) The growth rate of the diffusion zone followed the parabolic law. In the diffusion zone, the activation energy for diffusion of nitrogen was calculated to be 7.53×104 J/mol (1.80×104 cal/mol) by assuming the temperature dependency of the nitrogen concentration at the diffusion zone-compound layer interface.
    (2) The concentration of the nitrogen at the top surface of the compound layer was concluded as 11.35 wt% which corresponded to that of the ζ-Fe2N phase.
    (3) The growth rate of the compound layer followed the linear law during the first 30 min, after which it approximately followed the parabolic law. In the compound layer, the activation energy for diffusion of nitrogen was calculated as 8.46×104 J/mol (2.02×104 cal/mol) by assuming the top surface nitrogen concentration to be 11.35 wt% which corresponded to the ζ-Fe2N phase and the temperature dependency of the nitrogen concentration at the diffusion zone-compound layer interface.
    (4) The diffusion coefficient of nitrogen in the compoud layer was very small compared to that in the diffusion zone.
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  • Hazime Shimizu, Katsumi Hanji, Katsuhiko Ishiguro, Teiichi Homma
    1978 Volume 42 Issue 11 Pages 1071-1076
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    A microprobe-Auger electron spectrometry (μ-AES) method has been applied to a study on the transient oxidation of copper-nickel alloys at a low oxygen potential. The alloys containing 20, 40, 60 and 80 wt%Ni were oxidized under an oxygen pressure of 1×10−2 Pa at 350, 500 and 650°C. The surface composition of the polycrystalline specimens was measured in situ during oxidation using the μ-AES method. In oxidation at 500°C, nickel concentration of the surface changed with time and the behavior depended on a crystallographic orientation of the substrate alloy. Nickel concentration increased initially and then decreased after passing through a maximum value. At 350°C the tendency to change the surface composition was similar to that at 500°C, but showed a lower nickel concentration than the initial one during the decreasing stage. The nickel concentration increased markedly at 650°C and this trend of the increase continued during the oxidation in this study.
    Electron diffraction analysis revealed that the decrease after the nickel enrichment was due to covering of the Cu2O continuous film over island oxides in preference of NiO to Cu2O in the transient stage. It was during the transient filming of the alloy surface that the films formed non-uniformly due to the substrate crystallographic orientation effect. The transient film growth resulted in a steady state oxide scale structure which was composed of an inner NiO layer and an outer Cu2O layer.
    The μ-AES method has been proved to be effective for observing heterogeneous growth of thin oxide films.
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  • Hiroshi Eda, Kozo Kishi, Hisanori Taniyama, Satoshi Hashimoto
    1978 Volume 42 Issue 11 Pages 1077-1083
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    The object of this study is to grasp, from a fractographical point of view, the deformation and fracture formation process of grinding from the grinding start to the end. By grasping the formation phenomena some typical models are constructed which will contribute to the elucidation of the formation mechanism of grinding chips and ground surface layers. Fractographical observation has been made using a SEM which allows us to grasp the three-dimensional micro-and macro-behaviors of deformation and fracture in the vicinity of the grinding zone, chips-grinding point-ground surface. Some results obtained in this study are summarized as follows:
    (1) It is noted that chips and the ground surface are produced by such an interlocking system as
    (This article is not displayable. Please see full text pdf.)
    (2) Materials whose matrix involves excessively hard crystal grains show peculiar deformation and fracture behaviors in the chips zone and the ground surface layer: metal grains are crushed, cracked, and partly disappear. Moreover, slip lines, slip bands, and cup-or cone-shaped dimples are generated, flowing with the matrix.
    (3) From a morphological observation of the grinding zone some typical models are presented for theoretical analysis.
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  • Toshitada Shimozaki, Masami Onishi
    1978 Volume 42 Issue 11 Pages 1083-1089
    Published: 1978
    Released on J-STAGE: April 04, 2008
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    In the temperature range 583 to 673 K interdiffusion coefficients were determined in the concentration range about 74 at%Zn to the ε⁄η phase boundary.
    Concentration dependence of the coefficients underwent a change at about 83 at%Zn. The coefficients at solidus temperature of the ε phase, \Tilde{D}Tm, were constantly kept up to 82 at%Zn, where the following equation was held.
    (This article is not displayable. Please see full text pdf.)
    At composition of about 82 at%Zn Straalsund and Masson previously found an irregular change of zinc activity and attributed the activity change to an overlap of the Fermi surface across the Brillouin Zone. Because characteristic changes of the interdiffusion coefficient and the activity appeared at the same composition, the interdiffusion coefficient might be also affected by the zone overlap.
    From marker experiments it was estimated that the ratio of intrinsic diffusivity of zinc to that of silver were twenty to fourty and trended to decrease with increasing zinc content.
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  • Takayuki Takasugi, Osamu Izumi
    1978 Volume 42 Issue 11 Pages 1089-1095
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    Interface segregation behavior in α(fcc)⁄β(bcc) brass two-phase bicrystals and polycrystals was investigated by means of EPMA. The following facts were made clear from the results of this work.
    (1) Segregation profile in polycrystals was recognized as both the enrichment of Zn in β phase and the depletion of Zn in the α phase adjoining to the α⁄β interface. In two-phase bicrystals, however, the depletion of Zn in the α phase adjoining to the α⁄β interface was not observed.
    (2) The width and height of these segregation in two-phase bicrystals increased with increasing annealing temperature. More pronounced segregation was observed in the bicrystals than in the polycrystals.
    (3) It was explained by the crystallographic considerations that the segregation profile mentioned above was due to the character of the plane-matched interface structure. Furthermore, the interfacial energy and the lattice strain energy before and after the segregation were estimated. The energetic consideration also explained the experimental results reasonably.
    (4) A lack of the depletion of Zn in α phase adjoining to the interface in two-phase bicrystals was considered to result from the higher mobility of the interface than that of Zn atoms in the α phase.
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  • Hiroshi Yamagata, Osamu Izumi
    1978 Volume 42 Issue 11 Pages 1096-1103
    Published: 1978
    Released on J-STAGE: April 04, 2008
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    Deformation and grain boundary fracture behaviours of α brass bicrystals were examined. The results are summarized as follows:
    (1) The temperature dependence of the ductility of α brass bicrystals accompaning intergranular fracture is similar to that observed in α brass polycrystals.
    (2) The transition from transgranular to intergranular fracture starts at about 470 K and again a transgranular fracture appears at about 770 K: i.e., the intergranular fracture occurs in the temperature range of 470 to 770 K. It is note worthy that the lower transition temperature (470 K) corresponds to the onset of the inverse temperature dependence of yield stress. Also, the temperature at which the minimum value of ductility reveals coincides with that at which a peak in the yield stress appears.
    (3) Though the intercrystalline fracture accompanies the separation at the grain boundary plane macroscopically, it is a ductile fracture in the neighbourhood of grain boundary microscopically. Thus, apparent intergranular fracture seems to be caused by the coalescence of micro cleavage cracks along {111} planes, which are induced by the stress concentration due to dislocation pile-ups.
    (4) From those observations mentioned above, it is clear that the dynamic strain aging behaviour plays an important role in the intergranular fracture of α brass bicrystals.
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  • Hideaki Kawabe, Muneharu Takeuchi, Nobuyuki Shinohara
    1978 Volume 42 Issue 11 Pages 1103-1109
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    In order to clarify the formation mechanism of work-hardened layer introduced at the time of frictional or abrasive working, (001) planes of pure Al and Cu single crystals are scratch-deformed by diamond cone styli as a simplified model of working. The deformed structures around the end of the scratch-grooves in [100] and [110] directions and also the cross-section of the groove are examined by selected area ECP using SEM, and the results are compared with those by TEM. The following results are obtained:
    (1) By the scratch deformation, the regions where crystals are bent and rotated are introduced around the end of scratch groove and under the groove. The form of the region, the amount of crystal rotation and the direction of rotation depend on the scratch direction. The amount of rotation, especially, depends on the cone angle of stylus.
    (2) In the case of Cu single crystal, the regions, in which crystal has rotated with respect to ⟨211⟩ axis, can be classified by comperatively clear boundaries between them. Thus the activated region of slip systems contributing to the crystal rotation can be estimated at the time of scratch deformation.
    (3) Through the observations around the end of the groove by TEM, the process of variation of dislocation structures during the procession of stylus can be traced. As the result shows, cell walls are formed along the slip planes which are activated at the time of crystal rotation. Also, the increment of dislocation density is recognized in the regions which suffer several different slip processes and at the boundary regions which are formed by the regions of different rotational direction.
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  • Katsumi Kushiya, Katsuhisa Sugimoto, Tatsuhiko Ejima
    1978 Volume 42 Issue 11 Pages 1109-1114
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    Anodic polarization curves for a solution-treated or sensitized SUS 304 stainless steel and solution-treated Fe-Ni-Cr ternary alloys containing 10%Ni and 6 to 14%Cr have been measured in deaerated 0.5 mol/l Na2SO4 solutions of pH 2.0 to 5.9 at 298, 523 and 553 K. Corrosion potentials for U-bend SCC test specimens of sensitized SUS 304 stainless steel have also been monitored for a long time in the same solutions as those used for the polarization measurements except that they were aerated.
    It was found that the differences in the current densities in the passive state, ipass, between the solution treated steel and the sensitized one and also between the ternary, alloy with higher Cr content and the one with lower Cr content become large with increasing temperature and decreasing pH. This means that the difference in the values of ipass between grain bodies and Cr-depleted zones along grain boundaries of sensitized steel becomes larger and susceptibility to intergranular corrosion of the sensitized steel in the passivation region becomes higher with increasing temperature and decreasing pH. Since corrosion potentials for the U-bend SCC test specimens in air-satulated solutions lie in the passive region of anodic polarization curves for the sensitized steel in deaerated solutions, the intergranular stress-corrosion cracking of the sensitized steel in high temperature water with dissolved oxygen is considered to be caused by the preferential corrosion in the Cr-depleted zone.
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  • Toyojiro Isano
    1978 Volume 42 Issue 11 Pages 1115-1122
    Published: 1978
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    The intergranular corrosion of Fe-28%Cr alloy was studied by the corrosion test (boiling solution of 50%H2SO4 containing 25 g of Fe2(SO4)3) and by “local” anodic polarization measurements in which only the local region near a grain boundary groove is involved in the polarization process.
    On an anodic polarization curve of the grain boundary groove in the sensitized alloy, a current “halt” in the transition region from the active to the passive state was observed, which could not be observed in the anodic polarization curves in the non-sensitized alloy. The alloy was sensitized by solution heat treatment at 1100°C followed by air cooling or rapid cooling and reheating at 600°C for 10 min.
    The current “halt” was shifted to a more noble potential as the corrosion resistance of the alloy became lower. The current “halt” is ascribed to the existence of a chromium depleted zone or the α and α′ two phase formation due to spinodal decomposition.
    In the alloy reheated at 475°C the anodic current “halt” was always observed at −0.33 V regardless the corrosion resistance of the alloy.
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  • Hajime Suto, Shin-ichi Yamanouchi
    1978 Volume 42 Issue 11 Pages 1122-1126
    Published: 1978
    Released on J-STAGE: April 04, 2008
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    The effects of P, Mo and H on the low temperature temper embrittlement of 0.6%C-Mo-P steels have been investigated for V-notched specimens by means of a slow bend test and by Auger electron spectroscopy of the intergranular fracture surfaces. The results are summarized as follows:
    (1) The effect of P on temper softening is very small, but the contribution to embrittlement is very large.
    (2) Most of the P, S, Mo segregations to grain boundaries occur during austenitization, but a slight enrichment of the P segregation with tempering temperature is observed.
    (3) Mo additions suppress in some measure the P segregation to grain boundaries, but decrease the ductility of steel as a result of the increased resistance to temper softening.
    (4) Hydrogen embrittlement enhances the contribution of P to the low temperature temper embrittlement, in the sense that hydrogen decreases the fracture strength to 1/2.5∼1/3 independently of P-content.
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