All issues
Volume 59, Issue 5
Displaying 1-20 of 20 articles from this issue
- |<
- <
- 1
- >
- >|
-
Takashi Yoshikawa, Fukuji Inoko1995 Volume 59 Issue 5 Pages 471-479
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to clarify the effect of activated slip systems on the grain boundary premelting-like behaviour in thin foils of two kinds of 99.999 mass% silver bicrystal specimens, which have the same grain boundary and different tensile directions, were prepared using a modified Bridgman method. They were deformed in tension to a strain of 0.3. TEM foils containing the grain boundary were prepared. They were then subjected to in-situ heating experiments in a 200 kV TEM. The melting of grain boundary occurred at lower temperatures in the bicrystals whose boundary planes are parallel to screw dislocations of the activated slip systems than in the bicrystals whose boundary planes are parallel to edge dislocations. The grain boundary premelting-like behaviour in silver bicrystals is similar to that in copper ones.View full abstractDownload PDF (1341K) -
Yutaka Takahashi1995 Volume 59 Issue 5 Pages 480-486
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe molecular statics method [J. Japan Inst. Metals., 57(1993), 597] was developped, to calculate the static equilibrium state of pair-potential system, based on the principle of minimum potential energy in statics. The method was extended to Finnis-Sinclair type potential problems using the effective pair-potential approximation. The rate of convergence was increased by over an order of magnitude for large model when it was compared with conventional steepest descent method. To show an applicability of the method to lattice defect problems, the core structure of an edge dislocation and its Peierls stress were calculated in iron and gold.View full abstractDownload PDF (703K) -
Masaru Nakayama, Akira Furuta, Yasuhiro Miura1995 Volume 59 Issue 5 Pages 487-491
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAge hardening and precipitation processes in an Al-0.23 mass%Sc alloy were studied by hardness and electric resistivity measurements and by TEM observation. Stable, coherent L12-Al3Sc phase precipitates directly from a supersaturated solid solution without the formation of any metastable phases. A plot of the cube of the particle radius against aging time follows a straight line, suggesting that the coarsening process obeys the LSW theory of diffusion controlled particle coarsening. The apparent activation energy for the precipitation of the Al3Sc phase as determined by resistivity measurement is 76 kJ/mol.View full abstractDownload PDF (498K) -
Qi Cui, Goroh Itoh, Motohiro Kanno1995 Volume 59 Issue 5 Pages 492-501
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAge-hardening characteristics and precipitate structures in Al-4.06%Cu-0.36%Mg (Ag-free alloy) and Al-3.94%Cu-0.30%Mg-0.38%Ag (Ag-bearing alloy) alloys have been examined using conventional TEM, high-resolution TEM (HRTEM) and cold field emission TEM (FETEM) in order to clarify the effects of silver addition on the nucleation of the Ω-phase. In the Ag-free alloy, the Ω-phase nucleated mainly on a dislocation loop, and this caused a coarser distribution of the Ω-phase compared with that of the θ′- and S′-phases. In contrast, the density of the Ω-phase was markedly higher than that of the θ′- and S′-phases in the Ag-bearing alloy. The lattice images and “nano-diffraction patterns” (beam diameter, 0.6-1.0 nm) clearly revealed the presence of the G.P. zones, monolayer disks on the {111}Al planes, at the early stage of aging in the Ag-bearing alloy. Two-layer G.P. zones and G.P. zones with a partly different lattice structure were also observed occasionally. The nano-analysis with FETEM demonstrated that both the G.P. zone and Ω-phase are rich in copper, silver and magnesium. It was also found that when the G.P. zone formation was suppressed in the Ag-bearing alloy by an aging at 225°C after a quench in molten salt at this temperature, the Ω-phase precipitated heterogeneously with very low density. From these results, it is concluded that the homogeneously dispersed Ω-phase is formed exclusively through a continuous structural change of the G.P. zone on {111}Al.View full abstractDownload PDF (3432K) -
Hidemichi Fujiwara, Tatsuo Sato, Akihiko Kamio1995 Volume 59 Issue 5 Pages 502-511
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAn influence of small additions of phosphorous on the precipitation in Cu-1 mass%Fe alloys has been studied.
The number of γ-Fe particles that precipitated from the solid solution depend on the solution temperature and the phosphorous content. The rate on nucleation of the γ-Fe increases with an increase in the solution temperature and the phosphorous content up to 0.008 mass%. The increase of phosphorous over 0.012 mass% decreases the nucleation rate of the γ-Fe and causes the precipitation of Fe3P. The hardness change in the precipitation precess decreases with an inclease in the solution temperature and the phosphorous content up to 0.008 mass%. The hardening mechanism suggests that the increase of numbers of precipitates causes the decrease in hardness. It seemd that the variation in nucleation rate with changing solution temperature and the phosphorous content is affected by the formation of solute-vacancy clusters.View full abstractDownload PDF (1626K) -
Kazuya Miyahara, Jung-Hwan Hwang, Yukio Shimoide, Takashi Iwamoto, Yuz ...1995 Volume 59 Issue 5 Pages 512-518
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESS9-12%Cr-Mo ferritic heat resisting steels are widely used as high-temperature materials in the steam-power or chemical plants. It is reported, however, that the degradation of ductility is caused by the Laves phase (Fe2Mo) formed during a long-term service at high temperature and that Si has an effect to enhance the precipitation of the Laves phase. In the present research, a detailed study of the precipitation behavior of the Laves phase has been made using simple Fe-10%Cr-Mo-Si ferritic alloys, and the quantitative analysis of the effects of Mo and Si on the bulky Laves phase formation has been performed. Very fine disk like precipitates are formed on the {100} planes of the matrix before the bulky Laves phase formation and these fine precipitates cause a hardening peak except for the hardening due to the bulky Laves phase. The large effect of Si to enhance the precipitation of the Laves phase has been confirmed for the Fe-10%Cr-0 to 5%Si-2 to 10%Mo alloys.View full abstractDownload PDF (1855K) -
Yasuo Fujinaga, Yasuhiko Syono1995 Volume 59 Issue 5 Pages 519-524
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPressure dependence of the lattice parameters a and c of hexagonal boron nitride (h-BN) was measured by means of an in situ X-ray diffraction method. The mean compressibilities between 0 and 6.3 GPa were evaluated to be σa(Δa⁄aΔP)=1.4×10−12 m2/N and σc(Δc⁄cΔP)=1.8×10−11 m2/N. According to the large anisotropic compressibility the axial ratio c/a = 2.6578 at atmospheric pressure reduces to 2.373 at 6.3 GPa.
A diagram constructed from the correlation between the lattice spacing of h-BN and pressure can be applied to evaluate the pressure value in the solid medium without using the conventional pressure calibrating materials. The diagram can also be used as a simple method for determining d-values of h-BN under various pressures.View full abstractDownload PDF (582K) -
Kai-Jiang Wang, Kenji Wakashima, Masayoshi Ono1995 Volume 59 Issue 5 Pages 525-531
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe time-of-flight (TOF) analysis method in neutron diffraction has been applied to the study of residual stress states associated with the mechanisms of back-stress hardening and diffusional recovery in a short fiber-reinforced metal matrix composite. The composite examined was an experimental model system, Al3Ni whisker-reinforced aluminum, produced by directional solidification of the Al-6.2 mass%Ni eutectic alloy. It was cold-swaged and then annealed, so that very long (essentially continuous) whiskers changed into short fiber morphologies. Incremental strain amplitude tension-compression tests were carried out at room temperature and 500°C up to the total strain of 0.3% with final unloading from the tension side. Neutron diffraction experiment was subsequently performed to measure residual lattice strains in the deformed specimens, together with the as-annealed one as the reference material. A couple of detectors were properly arranged so as to make simultaneous measurements of lattice spacings in both the axial and transverse directions of the specimens. From the set of diffraction data, residual lattice strains and hence, residual stresses in both the axial and transverse directions were fully determined for the alminum matrix in the specimens deformed at room temperature and at 500°C; however, the corresponding residual stress states for the Al3Ni whiskers were indeterminable because of incomplete diffraction data due to the effect of preferred orientation of the Al3Ni whiskers. The results are discussed in light of independent calculations of residual stresses based on a micromechanics-based analysis of the stress-strain data in tension-compression tests.View full abstractDownload PDF (654K) -
Akio Sugiyama, Yukako Matsumoto, Koichi Arai, Sumiko Sanuki1995 Volume 59 Issue 5 Pages 532-539
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe reductive stripping of Pd and Pt from Pd(II), Pt(II) and Pt(IV)-loaded organics was investigated using NaH2PO2. The organics employed in this study were TBP and Alamine 336 diluted in kerosene. The main findings are as follows: (1) Pd particles of around 1 μm can be effectively stripped from Pd(II)-loaded TBP solution by using an excess amount of NaH2PO2 of 5 molar equivalents. The addition of 0.1 kmol·m−3 NH3 to the aqueous NaH2PO2 solution enhances the precipitation efficiency. (2) Pd can be reductively stripped from Pd(II)-loaded Alamine 336 by mixing the organics with an aqueous NaH2PO2 solution, followed by the addition of NH3 prior to reagitating the solution. In order to quantitatively strip Pd(II) from this organic phase, the addition of NaH2PO2 of 7∼10 molar equivalents to Pd(II) and 1 kmol· m−3NH3 is required. Pd particulates are obtained by using less than 5 molar equivalents of NaH2PO2, while a further addition of NaH2PO2 forms film-like precipitates. (3) Pt precipitation reaction from the organics containing Pt(II) and Pt(IV) is impossible under the experimental condition suitable for the reductive stripping of Pd from the organics containing Pd(II). The authors also discussed the possible mechanisms of these reductive stripping reactions.View full abstractDownload PDF (1583K) -
Shoichirou Taira, Kunihiko Nakashima, Katsumi Mori1995 Volume 59 Issue 5 Pages 540-546
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDissolution rates of silicon nitride ceramics into CaO-SiO2-10 mass%Al2O3 slags were measured by rotating specimen method. Experiments were conducted at various revolution speeds, temperatures, and CaO/SiO2 ratios. Moreover, the solubility of Si3N4 into the slags were measured to calculate the mass transfer coefficients of Si3N4. Based on these results, the dissolution mechanism of silicon nitride into the slags was discussed.
The dissolution rate of silicon nitride ceramics increased with increasing revolution speed and rising temperature. These results suggested that the dissolution rate was controlled by mass transport in the boundary layer of molten slags. The dissolution rate of silicon nitride increased slightly with increasing CaO/SiO2 ratios. This increase of the dissolution rate is attributed to the increase of the diffusivity of the solute accompanied with the decrease of slag viscosity with CaO/SiO2 ratios.
The chemical analysis of the slags after immersing silicon nitride ceramics showed that almost nitrogen in slags existed as N3− ions. On the other hand, the quantity of CN− ions was negligible, though the existence of CN− ions was confirmed. From the estimation of the interdiffusion coefficient DCaO-Si3N4 in the molten slags using JD-factor, it was found that DCaO-Si3N4 was a little smaller than DCaO-SiO2. From this result, it was reasonable that N3− ions existed in the molten slags incorporated into silicate network such as silicate complex anion. These results showed that the dissolution of silicon nitride proceeded by the diffusion of the N3− ion incorporated into silicate anions.View full abstractDownload PDF (735K) -
Shinji Hirai, Shougo Aizawa, Kazuyoshi Shimakage, Kenji Wada1995 Volume 59 Issue 5 Pages 547-553
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA zirconium oxide has been coated on aluminum anodic oxide with micro pores by a sol-gel process using zirconium alkoxide, and the alkaline corrosion resistance of its composite film has been examined by an electromotive force measurement method.
The main results obtained are summarized as follows:
(1) Micro pores of the aluminum anodic oxide film were charged by the zirconium oxide with an increase in dip-coating number of sol-gel solution, and a thin coating layer of the zirconium oxide was finally formed on aluminum anodic oxide film. The coating layer consisted of fine amorphous zirconium oxide particles. Defects and bubbles could not be observed in the coating layer by scanning electron microscopy.
(2) Alkaline duration time of the coating composite film evaluated by the electromotive force measurement method increased with increasing dip coating number. The alkaline corrosion resistance of the coating composite film was extremely improved when the thin coating layer was formed on aluminum anodic oxide film. Since the vibration behavior of voltage was observed in the duration time curve of the electromotive force mesurement, it was found that the composite film had a self-repairing action for alkaline corrosion.
(3) The composite film dried in air had alkaline corrosion resistance superior to that in nitrogen. In addition, the composite film formed by a heating treatment in oxygen had alkaline corrosion resistance superior to those in air and argon.View full abstractDownload PDF (1130K) -
Osamu Ise, Jun Onagawa, Takao Goto, Nobuo Ishii, Takashi Horikawa1995 Volume 59 Issue 5 Pages 554-558
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe microstructure and corrosion resistance of Ti-Pt alloys prepared from Ti and Pt powders by the Spark Plasma Sintering (SPS) method was investigated. The microstructure of SPS’s specimens were observed by scanning electron micrographs and X-ray diffraction patterns. Pt phases were dispersed in the Ti matrix, and a few intermetallic compounds of Ti-Pt were formed around the Pt phases. The corrosion behavior of SPS’s specimens were evaluated by potentiostatic polarization measurement in a 5 mass%HCl solution. The Pt and Ti3Pt phases may be responsible for high corrosion resistance, and the cathode reaction on Pt phases keeps passive state Ti. Therefore, the Ti matrix becomes appreciably more passive compared with the arc melted Ti-Pt alloys. In this method, the corrosion resistance was improved by adding only a few mass% of Pt.View full abstractDownload PDF (1306K) -
Goro Arakane, Susumu Takamori, Yoshiaki Ohsawa, Akira Sato1995 Volume 59 Issue 5 Pages 559-563
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe purpose of the present study was to develop a new process named “Rapid solidification with vigorous agitation”, by which large ingots having fine-grained and homogeneous structure can be produced. The molten Al-Si alloys containing 5, 12.6 and 20 mass%Si were rapidly solidified with water-cooled copper molds 30, 50, 75 and 100 mm in length and 50 mm in inner diameter, and at the same time were stirred vigorously at rotation speeds of 8, 17, 33, 67, 83, 100, 133 and 167 s−1 by graphite rods 35, 40 and 45 mm in diameter during falling down of the melt through a gap between the mold and the stirring rods. The molten alloys with superheats of 20 to 100 K were poured into the gap at a speed of 50 g/s between the mold and the stirring rods. Ingots were made by collecting slurries in containers kept at determined temperatures. The results are as follows. The mean grain size of solid particles in slurry become smaller with increasing the intensity of cooling and the rotation speed of stirring rod. That is, the grain size become smaller with decreasing the clearance between water-cooled copper mold and stirring rod, increasing the length of water-cooled copper mold and the rotation speed of stirring rod. The grain size of ingots increases with increasing the temperature of containers. The fluidity of slurry is the most important factor to make good ingots having fine grained structures. The temperature of container of slurry is also important to prevent grain from coarsening. Primary and eutectic grains of Si in hypereutectic or eutectic alloys are not only small but also globular when the agitation is strong enough. The average size of primary Si in hypereutectic alloys is strongly affected by the rotation speed of stirring rod below 50 s−1, and decreases from about 90 μm to about 40 μm.View full abstractDownload PDF (887K) -
Toshio Yamauchi, Yoshinori Nishida1995 Volume 59 Issue 5 Pages 564-570
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe pressure infiltration of aluminum and the deformation mechanism of preform were investigated on fiber-reinforced aluminum composites fabricated by squeeze casting. The aluminum borate whiskers and alumina short fibers preforms were prepared as reinforcements. Pressure was applied mechanically by a punch, and the pressure change and the punch speed were measured during the infiltration of molten aluminum into fibers preform.
To analyze the correlation between the applied pressure and the location of infiltration front in preforms, the hardness along the infiltration direction in the composite was measured and the distribution of volume fraction was calculated by the distribution of hardness.
These experimental results agreed well with theoretical analysis developed using D’Arcy’s law. The deformation of fibrous preforms occurred due to compressive stress during infiltration by the molten aluminum.View full abstractDownload PDF (1118K) -
Kiyoshi Ichikawa, Yoshiji Kinoshita1995 Volume 59 Issue 5 Pages 571-577
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAn investigation was made on the refinement of microstructures and improvement of mechanical properties in intermetallic TiAl binary alloys containing 44, 49 and 54 mass% aluminum produced by the rheocasting in which the solidifying alloy was vigorously agitated at high rotation speeds of 15 to 70 rev/s of a stirrer immersed in the alloys in argon atmosphere. In the microstructure of the rheocast Ti-44 at%Al alloy such a lamellar structure as seen in the alloy solidified without stirring was destroyed completely, and an extremely refined microstructure composed of dispersed agglomeration aggregates was formed. The mean sizes of agglomeration aggregates and individual crystal grains of the Ti-44 at%Al alloy rheocast at a rotation speed of 70 s−1 were 6.4±3.7 μm and 2.2±1.3 μm in the major axis and 2.0±1.1 μm and 1.0±0.6 μm in the minor axis, respectively. However, oval lammellar grains were seen in the microstructure of the rheocast Ti-49 at%Al alloy and a lamellar substructure was observed in the oval primary crystal grains in the microstructure of the rheocast Ti-54 at%Al alloy. In the microanalysis of the Ti-44 at%Al alloy rheocast at 70 s−1 the uniform distribution of Al and Ti elements could be achieved by destruction of the lamellar structure with mechanical stirring, although the lamellar segregation was observed in the alloy solidified without stirring. The room temperature elongations of the Ti-44 at%Al alloy rheocast at 15 and 70 s−1 were 2.7 and 3.3%, respectively. They were higher than the elongation of the alloy solidified without stirring, i.e. 2.0%. The room temperature tensile strengths of the Ti-44 at%Al alloy rheocast at 15 and 70 s−1 were 359 and 468 MPa, respectively. They were also higher than the tensile strength of the alloy solidified without stirring, i.e. 245 MPa. The elevated temperature elongation and tensile strength of the rheocast Ti-44 at%Al alloys were improved as compared with those of the alloy solidified without stirring, although a fluctuation existed. The tensile strengths of the alloys rheocast at 70 s−1 and cast without stirring were 538 and 363 MPa at 1173 K, and 439 and 389 MPa at 1273 K, respectively.View full abstractDownload PDF (1870K) -
Masaya Ito, Katsumi Miyama, Tomo-o Tanaka, Masato Taniguchi, Seiji Mor ...1995 Volume 59 Issue 5 Pages 578-583
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThis work provides a novel process in which the highly hard steel and Si3N4 are strongly joined to each other. Heat-resistant steel, Kovar, NiCrMo steel and carbon steel were used as the metallic materials. Ni/W-alloys were inserted between Si3N4 and metallic materials as buffer layers.
The multi buffer layer of combined Ni/W-alloy/Ni which reduces the residual stress, gives over 400 MPa in joining strength for the combination of Si3N4/Heat-resistant steel. For Si3N4/Kovar, Si3N4/NiCrMo steel and Si3N4/carbon steel show the joining strengths of 370, 612 and 317 MPa, respectively. In the thermal shrinkage curves from brazing temperature to room temperature of the metallic materials, the heat-resistant steel and NiCrMo steel show a volume expansion due to the martensitic transformation which increases the joining strength.View full abstractDownload PDF (567K) -
Mitsuaki Matsumuro, Haruyuki Inui, Yasuharu Shirai, Masaharu Yamaguchi1995 Volume 59 Issue 5 Pages 584-585
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (349K) -
Haruyuki Inui, Yoshiki Toda, Kyousuke Kishida, Yasuharu Shirai, Masaha ...1995 Volume 59 Issue 5 Pages 586-587
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (249K) -
Haruyuki Inui, Yoshiki Toda, Yasuharu Shirai, Masaharu Yamaguchi1995 Volume 59 Issue 5 Pages 588-589
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (340K) -
Yasuharu Shirai, Takashi Murakami, Noriko Ogawa, Masaharu Yamaguchi1995 Volume 59 Issue 5 Pages 590-591
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (203K)
- |<
- <
- 1
- >
- >|