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Volume 60, Issue 8
Displaying 1-12 of 12 articles from this issue
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Kenji Ohkubo, Yoshihiro Terada, Satoshi Takizawa, Tetsuo Mohri, Tomoo ...1996 Volume 60 Issue 8 Pages 695-699
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThermal conductivity of B2 type intermetallic compounds, NiAl and CoAl, have been measured at room temperature on about thirty specimens of different compositions. The conductivity-composition plots are characterized by a sharp maximum at stoichiometry in both compounds. These are the first extensive observations of such phenomena in intermetallic compounds. Electrical resistivity data are also reviewed in a wide compositional range of B2 single phase field. The field dependence of the transport properities were evaluated in terms of the Wiedmann-Franz relation. A quantitative discussion for the influence of the defect structure on the properties is developed. The dominant carrier of thermal conduction in NiAl and CoAl seems to be electrons rather than phonons in the non-stoichiometric compositions.View full abstractDownload PDF (475K) -
Yutaka Takahashi, Yoshiaki Takada, Shigeo Kotake, Akihito Matsumuro, M ...1996 Volume 60 Issue 8 Pages 700-707
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCarbon 60 was pressure-treated at 3 and 5.4 GPa at 291-1073 K. No change was noticed at 291 K. It collapsed into graphite at 1073 K. Polymerized fcc-phase reported by Iwasa et al. was obtained at 373-873 K. The lattice parameter of the phase was measured at the atmospheric pressure to clarify the sintering temperature and pressure dependences. It decreased continuously from a=1.417 nm down to 1.32 nm as the sintering temperature increased, which indicates that the polymerization is thermally activated. The applied pressure was, however, hardly affected.
The polymerized phase was metastable at the ambient pressure but converted to a pristine phase (a=1.417 nm) by heat treatment. The endothermic reaction and the recovery of lattice parameter were observed at 500-550 K. After the transition, the structure modification still continued during prolonged heating, which suggests that the recovery was incomplete.
From the geometrical requirement of a truncated icosahedron molecule, we proposed the structure model of the polymerized fcc-phase based on the ring-opening reaction. Some considerations were also made for the T-P phase diagram proposed by Sundqvist et al.View full abstractDownload PDF (791K) -
Yuichi Nagai, Nobuhiro Tsuji, Tetsuo Sakai, Yoshihiro Saito1996 Volume 60 Issue 8 Pages 708-716
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe microstructure and texture of the aluminium strips produced by a melt direct-rolling method are inhomogeneous in the direction of sheet thickness. The regions near surface (about 30% thickness of the strip) show fine and equiaxed grains formed by geometric dynamic recrystallization and have a typical shear texture (⟨110⟩\varparallelRD fiber texture including the {111}⟨110⟩ and {001}⟨110⟩ orientations), while the center layer shows elongated grains and has a typical rolling texture. This inhomogeneity is due to the large shear deformation induced by friction during rolling. Near the surface, the microstructure shows no remarkable changes during annealing below 673 K, but the relative intensities of the {111}⟨110⟩ and {113}⟨110⟩ orientations increase. Relatively large \barr and very large Δr are obtained by the tension test of the direct-rolled strip and they vary with the textures depending on the annealing temperature. The present study has clarified that the melt direct-rolling method is useful to develop the {111} texture in aluminium strips by the introduction of large shear deformation during rolling.View full abstractDownload PDF (1838K) -
Takehide Senuma, Masaharu Kameda1996 Volume 60 Issue 8 Pages 717-726
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of the hot band grain sizes of 28 μm and 54 μm on the r value and the texture formation of cold rolled plain extra low carbon steel sheets has been investigated in a range of cold rolling reductions from 70 to 90%. The results are concluded as follows.
1. In the formation of the cold rolling texture, the refinement of the hot band microstructure increases the intensities of the orientations in the vicinity of {111}⟨112⟩ and {100}⟨110⟩∼{112}⟨110⟩, which indicates that the grain refinement of the hot bands plays a similar role like an increase in the cold rolling reduction. This phenomenon can be explained by the development of a sharp hot band texture and the constraint of deformation due to the increased grain boundaries.
2. The main orientation of the recrystallization texture changes from {111}⟨110⟩ to {111}⟨112⟩ due to the increase in cold reduction. The former might be preferred by the nucleation and the latter by the growth process. The grain refinement of hot band shifts this transition to a lower reduction.
3. Proper combinations of high reduction cold rolling and the grain refinement of the hot bands makes it possible to produce a excellent good deep drawable plain extra low carbon steel sheet with high r and low Δr.View full abstractDownload PDF (1127K) -
Xuyue Yang, Hiromi Miura, Taku Sakai1996 Volume 60 Issue 8 Pages 727-733
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSuperplasticity of the prior cold- and warm-worked 7075 aluminum alloy, especially the effect of prior cold-rolling on it, was studied in tension at 798 K and at various strain rates from 10−5 s−1 to 10−1 s−1. Continuous dynamic recrystallization takes place during hot deformation, leading to the evolution of fine grained structure. With increasing prior cold-rolling reduction, new finer grains are evolved faster in the unrecrystallzed matrices and their following coarsening is retarded up to higher strains. These are caused by the pancaking of initial grains developed by cold-rolling, which leads to the decrease in the shortest grain diameter. The strain rate dependence of flow stress and total elongation to fracture is affected sensitively by such a grain refinement, which improves the superplastic characteristics in the medium region of strain rate. It is concluded that superplasticity takes place in 7075 aluminum alloy cold- and warm-worked under appropriate conditions and can be controlled mainly by grain boundary sliding.View full abstractDownload PDF (1552K) -
Ken-ichiro Suzuki, Sirou Watakabe, Koji Nishikawa1996 Volume 60 Issue 8 Pages 734-743
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt has been proved that yttrium oxide has superior properties for the mold material in precision casting of Ti-6Al-4V alloy through basic studies on the reaction between one of plasma sprayed layers of oxides and liquid Ti-6Al-4V alloy during solidification. The reactivity estimated in terms of the maximum hardness and amount of oxygen absorbed in surface hardened layer formed at the surface of simple castings has good correlation with the high temperature stability of oxides evaluated by the standard free energy changes of formation of oxides, solution of oxygen and metallic constituents of oxides into liquid Ti-6Al-4V alloy. The hardness profile of the surface hardened layer has been quantitatively explained by the mechanism in which oxygen evolved from oxide instantaenouly after contacting with liquid Ti-6Al-4V alloy is absorbed and diffuses through liquid and solid layers of Ti-6Al-4V alloy castings.View full abstractDownload PDF (1368K) -
Y. Kato, N. Saito, Akio Fuwa1996 Volume 60 Issue 8 Pages 744-750
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThin Silicon films were deposited on non-crystal quartz glass substrates by hydrogen reduction of Si2Cl6 at temperatures from 650 to 900°C in a horizontal hot wall reactor. The microstructures of the thin silicon films deposited under various experimental conditions were analyzed. The thin silicon films deposited from 750 to 850°C have the highest degree of preferred (220) plane orientation with the ⟨111⟩ direction along the plane, and the cross-sectional morphology exhibits a columnar structure. The experimental values of the lattice spacing approach a value cited in JCPDS for the films deposited in a higher temperature range. In the lower temperature range the morphology of surface is flat and smooth, and in the higher temperature range the surface becomes uneven remarkably.View full abstractDownload PDF (838K) -
Keita Sirakami, Kenji Kobayashi, Hiroshi Kikuchi, Akio Fuwa1996 Volume 60 Issue 8 Pages 751-756
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSExperimential observation of SiO2 precipitation reaction on a Si substrate through thermal decomposition of TEOS was pursued as functions of temperature, TEOS concentration and residence time where the gaseous reaction products identified by the atmospheric mass-spectrometer are C2H5 and C2H5OH, from which the following reaction scheme can be proposed:
(1) The overall thermal decomposition reaction of TEOS to precipitate SiO2(s) can be expressed as follows:
(This article is not displayable. Please see full text pdf.)
(2) The gaseous reaction intermediate species observed is SiO(OC2H5)2, which may be produced by the following reaction:
(This article is not displayable. Please see full text pdf.)
(3) The oder of reaction with respect to the TEOS concentration obtained experimentally is from 0.2 to 0.5.
(4) The above-mentioned experimental observation, in which the step(c) is the rate controlling step and the oder of reaction is (1/3), leads to
(a) the thermal decomposition of TEOS to produce the intermediate:
(This article is not displayable. Please see full text pdf.)
(b) the adsorption reaction of the intermediate:
(This article is not displayable. Please see full text pdf.)
(c) the SiO2(s) precipitation from the adsorpted speciees:
(This article is not displayable. Please see full text pdf.)View full abstractDownload PDF (475K) -
Hitoshi Shinno, Kazuo Saito1996 Volume 60 Issue 8 Pages 757-764
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSNitrogen ions were implanted into r.f. sputtered Fe thin films to synthesize Fe16N2 iron nitride. When the film thickness was 250 nm, Fe16N2 was formed in the Fe films during nitrogen ion implantation without postannealing. From the intensity ratios of X-ray diffraction peaks, the maximum volume fraction of Fe16N2+α′-martensite was estimated to be about 60%. The volume fraction of Fe16N2 of this sample did not change after postannealing at 423 K for 3.6 ks.
When the film thickness was 50 nm, Fe16N2 was not formed during the ion implantation, but the volume fraction of α′-martensite exceeded 90%. Implanted nitrogens escaped from the surface of the as-implanted specimen during the postannealing, decreasing the volume fraction of synthesized Fe16N2. However, Cu coating on the ion implanted specimen prevented the nitrogen escape and increased the volume fraction of Fe16N2 markedly.View full abstractDownload PDF (686K) -
Mikio Ito, Kazuhiko Majima, Shigeru Katsuyama, Hiroshi Nagai1996 Volume 60 Issue 8 Pages 765-774
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSm2Fe17NX magnetic powders have been prepared by mechanical grinding (MG) in NH3 atmosphere and subsequent nitriding. The influence of the compositional difference of starting material and MG conditions on their magnetic properties have been investigated. The increase of MG time promotes absorption of nitrogen into powders during nitriding because of the activation of powders. However, too long MG treatment causes the decrease of nitrogen concentration and deterioration of their magnetic properties due to the diminution of Sm2Fe17 structure. Therefore, there is an optimum value of MG time. The grain size of about 100 nm being much smaller than the single magnetic domain size of about 270 nm is obtained by MG with a vibration mill. The best value of maximum energy product (BH)max of 50.7 kJ·m−3 (6.34 MGOe) is obtained by MG with the vibration mill and subsequent nitriding.
These powders have been also prepared by MG with a rotary ball mill whose mechanical energy is lower than that of a vibration mill. Though the powders obtained by MG in NH3 for 288 ks with a rotary ball mill have the sufficient nitrogen content of about 35000 ppm without subsequent nitriding, their magnetic properties are extremely deteriorated. The powders prepared by MG for 36 ks with a rotary ball mill and subsequent nitriding in N2 at 723 K for 21.6 ks show good rectangularity in the demagnetization curve and higher magnetization. The maximum energy product (BH)max and remanence are 129 kJ·m−3 (16.1 MGOe) and 1.0 Wb·m−2, respectively.View full abstractDownload PDF (1086K) -
Masahiro Ando, Tadashi Nishihara1996 Volume 60 Issue 8 Pages 775-780
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe concept of fractal dimensions has been applied to the description of the morphologies of graphite shapes of cast iron. The fractal dimensions of the image surfaces were experimentally determined by using the Box-counting theorem. The results obtained are as follows:
(1) The fractal dimensions of the gray iron changed corresponding to the types of flake graphite shapes.
(2) The Box-counting plots for the graphite shapes were classified into two linear parts characterized by two fractal dimensions. The fractal approach could be available to graphite shape characterization.
(3) The fractal dimensions of the matrices of cast irons were estimated to be about 1.99.View full abstractDownload PDF (570K) -
Yukio Inokuti1996 Volume 60 Issue 8 Pages 781-786
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to clarify the mechanism responsible for the ultra-low iron loss of TiN-coated grain oriented silicon steel sheet, the structure of TiN films and steel sheet in the vicinity of the near-surface of the (011)[100] single crystal of silicon steel was observed by transmission electron microscope (TEM). The sample for observation of TEM was taken initially by mechanical processing from a marked domain-refined area of the TiN-coated silicon steel sheet, and finally thinned by using the focused ion beam (FIB) technique.
Diffraction patterns of TiN films and silicon steel sheet were satisfactory, showing (110)TiN\varparallel(100)Si-steel, [1\bar11]TiN\varparallel[011]Si-steel. The degree of coherency between [1\bar11]TiN and [011]Si-steel showed a good value of 4.5%. An intermixed layer of TiN and silicon steel about 10 nm in width with fine transverse fringes was also observed.
It should be emphasized that the ultra-low iron loss in the TiN-coated silicon steel sheet obtained by inducing radical domain refinement can be achieved by good coherency between the TiN films and single crystal of silicon steel with (011)[100], namely, the Goss orientation, in which the difference of the thermal expansion coefficients of the ceramic TiN films and silicon steel sheet, after cooling from 973 K plasma coating to room temperature, strongly tensions the near-surface of the TiN-coated silicon steel sheet to the [100]Si-steel direction (elastic strain along one axis).View full abstractDownload PDF (950K)
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