Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 44 , Issue 1
Showing 1-16 articles out of 16 articles from the selected issue
  • Shinji Takayama, Tetsu Oi
    1980 Volume 44 Issue 1 Pages 1-6
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The effects of processing conditions on the physical properties of Fe40Ni40B20 amorphous alloys produced by a single roll-casting technique were investigated. In producing the amorphous alloys, the temperature of the melt was changed while the rotating speed of the roll and the melt ejection pressure were held constant. The rotating speed was also varied at fixed melt temperatures and ejection pressures. The crystallization and Curie temperatures, saturation magnetization, and hardness of the resultant as-quenched amorphous alloys were not changed when either the temperature of the melt or the rotating speed of a roll was varied. The remanence Br and the ratio BrB2 were also unchanged with the above processing conditions. However, a large monotonic increase in coercivity Hc was observed with increases in melt temperature, and it also decreased with roll speed. Isothermal annealing treatments of the above samples at 250°C revealed that: the higher the melt temperature, or the lower the rotating speed, the smaller is the amount of the change of Hc; i.e., these conditions produced a more stable as-quenched structure. These results are discussed in terms of the cooling rate in the casting and the state of disordered structure quenched into the amorphous alloy.
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  • Akio Fujihira
    1980 Volume 44 Issue 1 Pages 6-15
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The growth kinetics of graphite nodules is studied by means of optical microscopy. The graphite nodules showed parabolic growth kinetics and the growth rates changed significantly with pre-treatments as well as with graphitizing temperatures. In order to explain these behaviors, a model of rate controlling process was proposed in which the increments in the space occupied by the graphite nodules were assumed to be supplied by vacancy diffusion from the sources in the specimen to the graphite nodules mainly through the grain boundaries. Although this model is analogous to Birchenall’s model which assumed diffusion of Fe atoms away from graphite nodules, this differs from Birchenall’s mainly in a treatment of the driving force and of the diffusion path. This model was revealed to be consistent with the experimental results of (1) the magnitude of growth rate, (2) the change in the growth rate with pre-treatments, (3) the shape of graphite nodules along grain boundaries, and (4) other microscopic charactaristics. However the activation energies observed (200∼250 kJ/mol) could not be explained using this model.
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  • Akio Fujihira
    1980 Volume 44 Issue 1 Pages 15-24
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    A systematic explanation of nucleation behavior shown in the foregoing two papers is attempted. From the view point that void forming process plays an important role in forming graphite nodules, an assumption was introduced that “if there were expanding stresses in the matrix, i.e. the tendency to make voids, at the temperatures possible to graphitize, the nucleation of graphite is significantly enhanced”. Explanation, using this assumption, of the experimental facts, revealed that there are two types of nucleation mechanism in the pre-heattreated specimens: (1) Ac1 mechanisms, which are observed in the specimens pre-quenched from the temperatures below Ac3, utilize the expanding stresses in the austenite region, associated with the pearlite→austenite reaction, and the graphite nucleate in the austenite (martensite) regions. (2) Ar1 mechanisms, which are observed in the specimens cooled rather slowly through the Ar1 temperature (air or funace cooled), utilize the expanding stress in the ferrite, associated with the austenite→pearlite reaction, and the graphite nucleate in the pro-eutectoid ferrite regions. Discussions were made on the growth and the disappearance of “defects”, which are expected to exist in the pre-treated specimens and to start growth as graphite nodules after some incubation time, and also on the role of the “expanding stresses” introduced by pre-treatments.
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  • Hideki Tonda, Hidemitsu Takahama, Tatsuo Kawasaki
    1980 Volume 44 Issue 1 Pages 24-29
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Bulk zinc crystals having low dislocation density ∼108/m2 and without any sub-grain boundary were produced under the conditions mentioned below. Dislocations were observed on the {11\bar20} surface using an etch pit technique.
    (1) Rod single crystals were grown using the Bridgman method from high purity material which was refined from 99.99% zinc using five-fold distillations and one-fold rectification.
    (2) Bulk crystals shaped into parallelepiped of (3∼6)×(3∼6)×(30∼60) mm3 from the above crystals were annealed for 96∼384 h (345.6∼1382.4 ks) in the thermal cycle in which the temperature was changed between 573 K and 673 K with a period of 12 h (43.2 ks).
    (3) The atmosphere during crystal growth and annealing was 50%Ar and 50%H2 gas which was made to pass through P2O5 after platinum asbest in 823 K.
    \ oindentIt was concluded that the crystal perfection was affected remarkably by fine particles of zinc oxide in the crystals, since crystals purified by distillation only had lower perfections.
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  • Masayasu Kawahara, Ken-ji Morinaga, Tsutomu Yanagase
    1980 Volume 44 Issue 1 Pages 30-36
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    In order to consider the redox equilibrium of Ni3+\ ightleftarrowsNi2+ in silicate melts, the ESCA spectra of Ni2p3/2 level for the glasses of Na2O-SiO2-NiO and CaO-SiO2-NiO systems have been measured.
    The ESCA spectra of Ni2p3/2 level for these glasses shift from Ni3+ to Ni2+ side with increasing NiO content and (Na2O or CaO)/SiO2 molar ratio. The redox equilibrium of Ni3+\ ightleftarrowsNi2+ in silicate melts seemed to be represented by a R type equation in which lower valency ion increases with increasing O2− (basicity). The behavior of Ni ions in silicate melts was discussed by referring to the results about the physical properties and farinfrared spectra reported in the previous papers.
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  • Kenji Suzuki, Hiroyasu Mitani
    1980 Volume 44 Issue 1 Pages 37-43
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The dimensional changes of Cu-14 wt%Al-Ni mixed powder compacts, whose Al content is in the possible range to form γ′ martensite, was measured by dilatometric method on heating up to 950°C. The Ni content to give a maximum sintered density was determined by comparing the dimensional changes of the specimens after sintering. The influence of Ni content on the sintering behavior of Cu-14 wt%Al-Ni mixed powder compacts was investigated by means of the differential dilatometric method, the measurement of the sintered density and the direct observation through optical microscope and EPMA.
    The results obtained were as follows:
    (1) All specimens exhibited an abnormal expansion at about 550°C, and most part of this expansion was retained to the room temperature after cooling. The abnormal and retained expansion were minimum at 8 wt%Ni, then it could be confirmed that 8 wt%Ni was the most effective content for sintering of Cu-14 wt%Al-Ni mixed powder compacts.
    (2) The temperature of all the specimens rose abruptly at 550°C. The amount of the temperature rise increased linearly with increasing Ni content. Then it was found that the abnormal expansion was independent of the temperature rise of the specimens.
    (3) Increment of porosity obtained from microscopic observation of the specimens after quenching from 700°C and also the specimens after sintering at 950°C for 4 h were proportional to the amounts of the abnormal and the retained expansions of the specimens respectively. This indicated that the increment in porosity should be directly related to the abnormal expansion.
    (4) From the microscopic observation of Cu-Ni mixed powder compacts including Al wire which were quenched after heating up to 700°C, the minimum amount of the retained pores could be found in the model specimen of Cu-9.3 wt%Ni which was equivalent to the Cu-14 wt%Al-8 wt%Ni composition, corresponding to the results above mentioned in (3). Judging from the results of line-analysis on these model specimens through EPMA, τ(Cu3NiAl6) phase tends to be formed most easily in this specimen, where the τ phase seems to interfer the pore-formation.
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  • Kenji Suzuki, Norihiko Nakanishi, Hiroyasu Mitani
    1980 Volume 44 Issue 1 Pages 43-47
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Measurements of internal friction and Young’s modulus were made by a bending vibration method with a frequency of about 520∼680 Hz in a temperature range from 293 K to 433 K on the Cu-13.8 wt%Al-7.9 wt%Ni alloys obtained at various cooling rates after solution heat-treatment at 1223 K for 1.8×103 s, where effects of cooling rates on the temperature behavior and the values of internal friction were discussed.
    It was found that the main-peak (Pm) always appeared at a constant temperature of 323 K in all specimens which were cooled at the rates between 3.8×10−2 and 53 K/s, and besides Pm sub-peak (Ps) appeared above 323 K in the specimens which were cooled at the rate of 5.5 K/s or more.
    With increasing cooling rates, the values of Ps increased and the temperature of Ps had a tendency to become lower. Curves of Young’s modulus and differential scanning calorimetry showed the minimum value and the maximum value respectively at the temperature appearing Ps; showing that Ps is the phase transformation peak.
    The values of Pm kept constant at the rate of 5.5 K/s or more after showing a linear increase with increasing cooling rate less than 5.5 K/s, where the values of Pm depended on the contents of γ′ martensite, and the single phase of γ′ martensite could be obtained from the specimens cooled at the rates beyond 5.5 K/s.
    From the above-mentioned considerations, it was suggested that the Pm was the twin-boundary relaxation peak of γ′ martensite.
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  • Yasunori Hayashi, Mitsugu Nagano, Namio Ohtani
    1980 Volume 44 Issue 1 Pages 48-52
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    An alternating current method of electrochemical hydrogen permeation was discussed to obtain the diffusion coefficient of hydrogen in iron at low temperatures. The diffusion coefficient of hydrogen was evaluated from the frequency dependence of the phase difference between anodic permeation current and cathodic charging current. This method enables us to separate the surface effect from the permeation process, and gives an accurate diffusion coefficient. The diffusion coefficient of hydrogen in electrolytic iron was obtained by this method at temperatures between 233 and 303 K. The result is not expressed by a single Arrhenius equation. For electrolytic iron, even in a single crystal, the trapping effect is significant at low temperatures.
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  • Kazuo Nagata, Seiichi Nishikawa
    1980 Volume 44 Issue 1 Pages 53-60
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Precipitation processes during isothermal aging and step-annealing of Cu-2.46, 0.99. 0.52%Fe alloys were investigated mainly by electrical resistivity measurement, hardness test and transmission electron microscopy.
    The principal results obtained were as follows:
    (1) The clustering or precipitation reaction occured during quenching were drastic, especially in the alloy of high Fe content. (2) The anomalous electrical resistivity increase due to reversion of quenching clusters was observed during the isothermal aging of 0.52%Fe alloy at relatively high temperatures. The resistivity increment increased as the aging and solution temperatures rised, the quenching rate slowed down and the size of specimens became larger. (3) The precipitation process during step-annealing were sub-divided into two stages by an intermediate reversion process of clusters. The apparent activation energy for the initial precipitation in 2.46%Fe alloy was 216 kJ/mol and nearly equal to that for impurity diffusion of Fe in copper. The energy was lowered as Fe content decreased. (4) The growth of γ-Fe particles was expressed by the t1⁄3 law of Ostwald ripening after completion of precipitation. The coherency contrast of spherical γ-Fe particles was still maintained even under the complete over-aging condition.
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  • Kazuo Nagata, Seiichi Nishikawa
    1980 Volume 44 Issue 1 Pages 61-67
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The isothermal reversion process of Cu-2.46%Fe alloy, the effect of cold working on the process and the anomalous increase in electrical resistivity introduced by cold working in as-quenched and aged alloys were investigated.
    The main results obtained were as follows:
    (1) The amount of reversion increased with increasing difference between aging and reversion temperatures and also, with increasing aging time. (2) The critical pre-aging temperature above which reversion phenomena were not observed did not exist. (3) The reversion process was well expressed by the 1st order rate equation and the estimated value of activation energy for reversion (136 kJ/mol) was considerably smaller than that for impurity diffusion in copper. (4) By cold working before aging, the amount of reversion was greatly reduced in the case of reversion at lower temperatures, but increased more than that in an undeformed specimen at higher reversion temperatures. On the contrary, in the case of cold working after aging, the reversion phenomena were not observed. (5) Astonishingly large increase in resistivity was observed, which could not be explained only by the introduction of dislocations or other lattice defects by cold working. The results seemed to be explained by the redissolution of refined precipitates rather than the refinement of precipitates by cross-cutting action of dislocations.
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  • Yuji Tsukamoto, Hiroaki Sasaguchi, Fusao Hayama
    1980 Volume 44 Issue 1 Pages 68-75
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    This paper describes an investigation of the prow formation processes taking place on the various brasses rings (97 mm in diameter) sliding against a hemispherically-ended mild steel pin. In this investigation it is assumed that the friction and wear behaviours depend on both the size of a prow formed between two bodies and the position where the prow breaks away.
    The experiments show that a prow formation process observed on α brass is different from those observed on α+β and β brasses. A prow formed on α brass grew and broke away at a very short sliding distance from a few millimetres to at most a few centimetres. On the other hand, a prow of α+β or β brass continuously grew over a few revolutions, and the prow could often be seen even without the aid of the microscope, although a portion of it fell off as a loose wear particle or a transferred fragment.
    In order to obtain more detailed informations about the prow formation processes, size and shape distributions of loose wear particles and transferred fragments were examined. The transferred fragment defined in this paper corresponds to the prow broken away near the initial contact region between two specimens, and the material of it is continuous with that of the ring specimen.
    The distributions of the transferred fragments were significantly different for the various brasses, both in size and in number. Larger transferred fragments were found on the wear track of α brass in greater numbers than the others, and such heavily work-hardened transferred fragments prevented the continuous plastic shearing of α brass and reduced the wear. Large blocklike wear particles were formed on α+β and β by a loss of a portion of the prow or occasionally the entire prow, while flat platelike debris were mainly observed in the wear particles of α brass. A chiplike wear particle was produced by the cutting action of a large grown prow. The formation of this type wear particle may be equivalent to a kind of the prow formation except that the sheared material is not added to the prow.
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  • Syotaro Mizobuchi, Shigeki Kano, Kohichi Nakayama, Hideo Atsumo
    1980 Volume 44 Issue 1 Pages 76-84
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    A friction behavior of the hardfacing materials such as cobalt base alloy “Stellite” and nickel base alloy “Colmonoy” used in the sliding components of a sodium cooled fast breeder reactor was investigated in various sodium environments. Also, friction tests on these materials were carried out in argon environment. And they were compared with those in sodium environment.
    The results obtained are as follows:
    (1) In argon, the cobalt base hardfacing alloy showed better friction behavior than the nickel base hardfacing alloy. In sodium, the latter was observed to have the better friction behavior being independent of the sodium temperature.
    (2) The friction coefficient of each material tends to become lower by pre-exposure in sodium. Particularly, this tendency was remarkable for the nickel base hardfacing alloy.
    (3) The friction coefficient between SUS 316 and one of these hardfacing materials was higher than that between latter materials. Also, some elements of hardfacing alloys were recognized to transfer on the friction surface of SUS 316 material.
    (4) It was observed that each tested material has a greater friction coefficient with a decrease of the oxygen content in sodium.
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  • Mitsunobu Abe, Yasuji Kokabu, Yukio Hayashi, Satohiro Hayami
    1980 Volume 44 Issue 1 Pages 84-94
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The formation of cold rolling and recrystallization textures in pure iron having various grades of initial grain size has been investigated using X-ray diffraction, selected area electron diffraction, and etch pit techniques.
    For coarse grains in each of which the strains conformed to rolling are not attained by single slip, high dislocation density regions having {111} orientation are formed locally in the neighbourhood of initial grain boundaries during cold rolling. After subsequent annealing, {111} recrystallized grains appear preferentially in such regions near initial grain boundaries, that is, the initial grain boundaries contribute to an increase in {111} component during annealing. It is confirmed for specimens having initial grain sizes in the range of 25 to 300 μm that the {111} component in the recrystallization texture increases with decreasing the initial grain size.
    The process in which {111} nuclei grow into {112} and {113} matrices is dominant in the specimens with small initial grain size. In this case, the orientation differences between the nuclei and the matrices are expressed by rotations of 25∼30 degrees about ⟨110⟩ axes. A large number of adjacent two domains (smaller than the initial grains size) having the specific orientation relations mentioned above is frequently observed at cold-rolled and recovered stages. Moreover, these two domains in the recovered stage are bordered clearly by high angle boundaries, which disappear preferentially during recrystallization.
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  • Shigeo Sumita, Takashi Mimori, Ken-ji Morinaga, Tsutomu Yanagase
    1980 Volume 44 Issue 1 Pages 94-99
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Effects of Fe2O3 on the viscosity of silicate and ferrite slag melts have been studied in terms of the oxygen co-ordination number of Fe3+. Fe2O3 was amphoteric oxide like Al2O3 in these melts. Two parameters determining the behavior of Fe2O3 were proposed for these melts. One is the basicity of melts, and the other is the ratio of alkali (R2O)-, alkaliearth(RO)-oxide/Fe2O3 as seen for Al2O3. The portion of Fe3+ (4-co-ordinated oxygen) like Si4+ was increasing with increasing the basicity and/or the alkali-, alkaliearth-oxide/Fe2O3 ratio.
    In Na2O-Fe2O3 and BaO-Fe2O3 systems, the maximum was observed in viscosity-composition curves at the composition corresponding to Na2O or BaO/Fe2O3\fallingdotseq1. This could be explained by considering a change of the co-ordination number of Fe3+ with Fe2O3 content in the melts.
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  • Kazuyoshi Nii, Kazuhiro Yoshihara
    1980 Volume 44 Issue 1 Pages 100-106
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The segregation behavior of sulfur has been investigated on Fe(100) surface by AES and LEED in the temperature range from 873 to 1123 K. The bulk concentration of sulfur in specimens was varied from 17 to 100 wt ppm, which covered the areas both below and above the solubility limit of sulfur in α-Fe. In the area below the solubility limit, the equilibrium surface concentration of sulfur was about 30 at%, which was independent of the annealing temperature and the bulk concentration of sulfur. The surface structure c(2×2) was observed on the sulfur-segregating surface for all specimens. In the area above the solubility limit, the surface concentration of sulfur amounted to about 40 at% for some specimens, but the scattering of data between specimens was larger. From these results, it was concluded that the two-dimensional surface phase of Fe2S precipitates on Fe(100) surface below the solubility limit of sulfur and that the additional precipitation of bulk phase FeS occurs on the surface above the solubility limit. The thermodynamical consideration was given on the two-dimensional surface phases, and the attempt was made to construct the equilibrium phase diagram containing the surface phases. The qualitative representation of Fe(100)-S system has been given: (1) When the bulk concentration of sulfur is very small, the surface phase is in the state of solid solution, and the surface concentration increases with an increase in bulk concentration; McLean-type segregation. (2) If the bulk concentration exceeds a critical value (less than 1 wt ppm), the two-dimensional surface phase Fe2S precipitates, and the surface concentration of sulfur remains almost constant until the bulk concentration arrives at the bulk solubility limit (100 wt ppm at 1073 K). (3) Above this concentration, the three-dimensional FeS precipitates and coexists with the surface phase Fe2S on the surface.
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  • Hakaru Masumoto, Minoru Takahashi, Takafumi Nakayama
    1980 Volume 44 Issue 1 Pages 107-111
    Published: 1980
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The time-variations of magnetostriction and magnetization of rod shaped single crystals of Ni-25%Co alloy were observed in an external magnetic field of 6.4 kA/m at high temperatures. The magnetostriction and magnetization at room temperature were also measured in an external field of 82 kA/m when the specimens were slowly cooled in the furnace without magnetic field after their time variations had been terminated.
    The absolute value of magnetostriction decreased with time taking a relaxation phenomenon in a temperature range from 350 to 500°C. At the same time, the magnetization increased with decreasing magnetostriction and finally both values became gradually constant. These variations in the direction of easy magnetization at high temperatures were very remarkable and most of the values were retained down to room temperature. In the direction of hard magnetization, however, their variations were small and the values at room temperature after magnetic annealing returned to those prior to magnetic annealing. However, the activation energy calculated from the relaxation curves of magnetostriction and magnetization in both directions showed a value of about 2.7 eV. In this case the activation energy was a similar kind of energy required for the atom diffusion in a solid.
    It seems most probable that the magnetic annealing effect arises from the rearrangement and fixing of domains due to the relaxation of internal stress caused by magnetostriction at high temperatures. In this process, it is supposed that the constituent atoms of the crystals and impurities, and structural defets such as dislocations, vacancies, etc. are moving and diffusing.
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