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Volume 59, Issue 6
Displaying 1-14 of 14 articles from this issue
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Hiroshi Sato1995 Volume 59 Issue 6 Pages 593-598
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe isothermal section at 1073 K and the liquidus surfaces of the phase diagram of the pseudo-ternary SrO-Fe2O3-B2O3 system were determined in a composition range of the B2O3 content less than 50 mol% by using thermal analyses and X-ray diffraction. The liquidus surface which is in equilibrium with Fe3O4 sprends over a wide composition range and that in equilibrium with SrO·6Fe2O3 extends long and narrow to SrO·B2O3. The pseudo-ternary SrO-Fe2O3-B2O3 compound does not exist in the composition range investigated. The ternary eutectic reaction is L→SrO·6Fe2O3+SrO·B2O3+2SrO·B2O3, occurring at 1213 K at the composition 52 mol%SrO-18 mol%Fe2O3-32 mol%B2O3.View full abstractDownload PDF (409K) -
Norihisa Takahara, Makoto Takahashi, Ryuichiro Oshima1995 Volume 59 Issue 6 Pages 599-606
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThere have been few crystallographic studies on the phase transition of Fe rich Fe-Rh alloys and the phase diagram remained obscure in many respects. It was established that the alloys with higher Fe concentration undergo fcc-bcc martensite transformation by quenching from the high-temperature γ phase. However, no transmission electron microscope (TEM) investigation of the martensites has been reported, possibly due to the difficulty in preparing a good TEM specimen of the alloy with extraordinarily excellent corrosion resistance. Recently we have developed a technique to prepare a TEM specimen by electro-polishing and ion-milling, and examined internal structures of the martensites of Fe-5 at%Rh and Fe-25 at%Rh alloys by employing X-ray diffractometry, optical and transmission electron microscopy. The results are summarized as follows: (1) Both Fe-5 at%Rh and Fe-25 at%Rh alloys show surface reliefs, which are due to martensite transformation. (2) The martensites are of a dislocated lath type, whose lattice invariant shear is slip. Burgers vectors of the dislocations are ⟨111⟩ and ⟨001⟩ types. (3) In an Fe-25 at%Rh alloy twinning shear is also associated with the lattice invariant shear of the transformation. (4) The Kurdjumov-Sachs orientation relationship is observed between the retained γ and martensite phases of an Fe-25 at%Rh alloy.View full abstractDownload PDF (1436K) -
Susumu Onaka, Hiroki Kato, Satoshi Hashimoto, Sei Miura1995 Volume 59 Issue 6 Pages 607-611
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCrystal orientation and yield strength are studied for a magnesium ingot continuously cast by the OCC process. The ingot consists of elongated subgrains parallel to the solidification direction. The disorientation angles between neighboring subgrains are about 2 degrees. Overall orientations of the subgrains in the ingot are well aligned and the ingot has a monocrystal-like structure. Anisotropy of plastic deformation is observed for specimens cut from the ingot, which is similar to that in magnesium monocrystals. It is found that the presence of subboundaries increases the critical resolved shear stresses for the basal-slip system.View full abstractDownload PDF (467K) -
Xuyue Yang, Hiromi Miura, Taku Sakai1995 Volume 59 Issue 6 Pages 612-619
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of prior warm-deformation on microstructure development in superplastic 7075 aluminum alloy was studied by means of 2-step tensile testing and metallographic observation. In the case of warm-deformation to over a critical strain εpc at intermediate temperatures from 573 to 623 K, the microstructures developed exist quite stably for a long period of time (e.g. 106 s) compared with those cold-rolled (e.g. less than few seconds) or warm-deformed to below εpc, then leading to the appearance of superplasticity during deformation at high temperatures. New dislocations evolved by warm-deformation are pinned by η-phase particles which are reprecipitated during their coarsening or dissolving, and so the initial inhomogeneous microstructures change to the ones distributed homogeneously all over accompanied with dynamic recovery, when straining over εpc. The apparent activation energy for recrystallization decreases with its progress and finally approaches that for the self-diffusion of aluminum atoms. It is concluded that high density dislocations and fine particles reprecipitated on them can co-exist stably through their strong interaction and than static recovery as well as recrystallization taking place in such substructures can be retarded extensively at high temperatures.View full abstractDownload PDF (1571K) -
Masayuki Tendo, Tetsuro Takeshita, Takanori Nakazawa1995 Volume 59 Issue 6 Pages 620-626
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCreep behavior at room temperature has been investigated for austenitic stainless steels (18%Cr-14%Ni) with different contents of dissolved carbon and nitrogen. Creep strains of all the specimens satisfied a logarithmic creep law. Though the additions of both carbon and nitrogen increased the proof stress, the effects on the creep behavior were different between them. Comparing the creep strain at the normalized stress (applied stress/0.2% proof stress of specimens), carbon had little influence, whereas nitrogen increased the creep strain. Since the nitrogen addition increased the strain rate dependence of the flow stress for a tensile test, nitrogen had an effect of enhancing the thermally activated movements of dislocations and increased the creep strain. From the observation of dislocation structures after creep tests using a transmission electron microscope, the nitrogen-containing steels showed marked planar dislocation structures and many dislocation pile-ups. These dislocation structures were obviously different from those of the carbon containing steels and a high purity steel. Since the nitrogen effect on the creep was recognized at the high dislocation density produced by high applied stress, it is concluded that the dislocation pile-ups in the planar structure made stress concentrations, which enhanced the thermally activated movements of dislocations. Moreover, the activation volumes, calculated from the coefficients in the logarithmic creep law and measured from the stress changes in the strain-rate change tensile tests, were remarkably reduced by nitrogen addition. These were considered as an apparent reduction caused by the effective stress increased locally by the dislocation pile-ups.View full abstractDownload PDF (1353K) -
Mitsuharu Shiwa, Otis Y. Chen, Steve H. Capenter, Teruo Kishi, Shirou ...1995 Volume 59 Issue 6 Pages 627-633
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA SiC/SiC composite formed from woven sheets of carbon coated SiC fibers has been examined during the tensile loading of both un-notched and double-edge-notched specimens. As the specimens were deformed at a slow crosshead speed of 0.02 mm/min, the load, strain and acoustic emission (AE) were all measured and characterized. Analysis of AE amplitude distributions, coupled with the stress strain curves and SEM observations indicates that the fracture mechanisms of the SiC/SiC composite consist of matrix cracking, debonding, fiber pull-out and fiber breakage. The fracture surfaces of the un-notched specimens were characterized by fiber pull-out. The fiber pull-out was a result of the stress concentration due to pores located in the woven yarns which produced heavy matrix cracking leading to fiber bundle breakage. Different behavior was found for the notched samples which demonstrated quasi-yield behavior during tensile loading. The notch was found to produce a localized stress concentration inducing debonding of the 0° direction fibers. Then fiber pull-out occurred after the breaking of fibers without causing substantial matrix damage. In the SiC/SiC coposite, pores located in the woven yarns act as an initial defect which causes matrix cracking. The resultant stress concentration from the matrix cracking causes numerous localized fiber breaks.View full abstractDownload PDF (569K) -
Kazuo Kameda, Katsunori Yamaguchi, Toshiko Kon1995 Volume 59 Issue 6 Pages 634-639
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe activities of zinc in liquid Zn-In and indium in liquid Cd-In alloys have been determined by the emf measurements of the following galvanic cells:
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The emf values obtained for both systems showed a good stability with time and linear relationships with temperature.
The activities of the components in the Zn-In alloys at 900 and 1000 K and in the In-Cd alloys at 850 and 900 K exhibit moderately positive deviations from Raoult’s law over the entire concentration ranges, respectively. The activities of zinc and indium in the liquid Zn-In alloys were evaluated in a higher temperature range than those in the published data. Considering the temperature dependence, the positive deviations of activities from Raoult’s law in the Zn-In alloys are a little smaller than the previous values. The published data on the activities of indium of the liquid In-Cd alloys have been derived from the activities of cadmium based on a Gibbs-Duhem integration. In this study, the activities of indium of the In-Cd alloys are measured by a direct method. The behavior of activities of the In-Cd alloys in this study is similar to the previous data. The activity values of indium are in good agreement with the result by Heumann et al.
The activities of the components in the Zn-In alloys show reasonably greater positive deviations than those in the In-Cd alloys, owing to the larger differences of atomic radius factor in the Zn-In alloys.View full abstractDownload PDF (481K) -
Masahiro Okumiya, Hiromitsu Takeuchi, Yoshiki Tsunekawa1995 Volume 59 Issue 6 Pages 640-645
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSElectro-plating of an alumina particle/nickel composite system was carried out on an aluminum alloy substrate, in which an electrolyte jet was applied to improve the deposition rate and also to realize a required volume fraction of alumina particles. The turbulent jet increases remarkably the limiting current density which is the maximum value required to obtain a qualified deposit. The limiting current density increases as the jet velocity increases, regardless of the alumina concentration in the electrolyte and its average diameter. It is saturated with approximately 120×102 A/m2 at a jet velocity of 4 m/s and becomes 15 times larger than that in conventional plating without a turbulent jet. Alumina particles are then dispersed uniformly in the deposit. The volume fraction of the particle increases up to 30 vol% as the alumina concentration in the electrolyte increases. The volume fraction decreases as the jet velocity increases. It shows a maximum value at a particle diameter of 1.7 μm among the particles 2.8, 1.7 and 0.6 μm in diameter. The resultant deposition rate of alumina particle/nickel composite plating with the electrolyte jet is approximately 15 times faster than that of conventional electro-plating.View full abstractDownload PDF (959K) -
Keizo Hosoya, Katsuhisa Sugimoto1995 Volume 59 Issue 6 Pages 646-652
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEffects of water, anions, and dissolved oxygen content in methanol solutions on the corrosion of iron have been examined by immersion corrosion and electrochemical polarization tests. The corrosion of iron in methanol solutions was controlled by passivation behavior of iron. The passivity of iron was stabilized by water and dissolved oxygen in the solutions. In methanol with NaCl or LiClO4, iron exhibited no passivation when the water content was less than 0.05%, and iron showed active dissolution when the water content was more than 1%, and the dissolved oxygen accelerated passivation of iron in these solutions. In methanol without NaCl or LiClO4, however, iron exhibited clear passivation in the range of water contents up to 10%. Therefore, the corrosion of iron in methanol was found to be promoted by the addition of anion when the water content is more than 1% or less than 0.05%.View full abstractDownload PDF (769K) -
Makoto Yoshida, Takao Tsujimura, Muneo Kamata, Hideo Nakae1995 Volume 59 Issue 6 Pages 653-659
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe morphological transition of rods to lamellae with increasing growth rate in a Ni-W eutectic alloy was investigated. The eutectic alloy was directionally solidified in a Bridgman-type apparatus at the eight steps of growth rates from 1.0 to 16 mm/h.
The change in morphology with increasing growth rate appeared in the following two different ways of lamella formation:
(1) Under the conditon of the planar solid/liquid interface, the eutectic grain was uniformly comprised of rods or lamellae (blades). In this case, the deviation of the γ-phase ⟨100⟩ direction from the growth direction controlled the morphology.
(2) When cellular interface was formed at relatively higher growth rates, both rods and radial lamellae coexist simultaneously in a cell.
We confirmed that, as a common factor in the above two ways, the driving force of lamellae formation should be influenced by the angle between the γ-phase ⟨100⟩ direction and the local growth direction defined as being perpendicular to the solid/liquid interface.View full abstractDownload PDF (1097K) -
Hirofumi Miyahara, Ryuji Muraoka, Nobuyuki Mori, Keisaku Ogi1995 Volume 59 Issue 6 Pages 660-665
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of alloying elements on the wettability of molten aluminum to alumina substrate were investigated with the sessile drop method in a vacuum of 2×10−3 Pa at temperatures from 973 K to 1173 K.
The contact angle of molten aluminum on alumina substrate decreased from 109° to 92° as the temperature rose from 973 K to 1173 K. The alloying elements of 5.5%Cu, 15%Cu, 33%Cu, 1.1%Ni, 6%Ni, 10%Si, 0.15%Ti, 0.17%Be, 0.11%Zr and 0.47%Hf had little influence on the wettability to alumina. On the contrary, the addition of 4.1∼9.7 %Mg and 1.7∼4.2 %Li to molten aluminum lowered the contact angle by 10∼20°. Higher the content of these elements more improved the wettability.
Both Al-Li and Al-Mg alloys reacted with pure alumina in Ar atmosphere, and mass spectra and depth profile of positive secondary ions of Al+, Li+, Mg+, O+, LiAl+, LiAlO+, MgAl+, MgO+, etc. revealed that the 0.02∼0.13 μm thick LiAlO2 and MgAl2O4 were formed at the surface of alumina at 973 K. The thickness of LiAlO2 layer increased proportionately to (reaction time)1⁄2, the temperature and Li content, while the thin reaction layer of MgAl2O4 were almost unchanged even by longer holding until 3600 s at 1173 K.View full abstractDownload PDF (577K) -
Mikio Ito, Kazuhiko Majima, Shigeru Katsuyama, Hiroshi Nagai1995 Volume 59 Issue 6 Pages 666-672
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSUsing Sm2.5Fe17 alloy powder of-100 mesh, the preparation of Sm2Fe17Nx magnetic powder whose grain size is finer than the single magnetic domain size was carried out by mechanical grinding (MG), subsequent heat treatments for crystallization, nitriding and annealing. The effects of MG time and heat treatment on the factors such as the grain size, nitrogen and oxygen content, the precipitation of α-Fe and magnetic properties have been investigated. The results obtained are summarized as follows:
(1) The grain size of powders after MG was about 10-30 nm and it was extremely finer in comparison with the single magnetic domain size of about 300 nm. Although the grain size was coarsened by the subsequent heat treatments, it was about 50 nm even after annealing.
(2) The precipitation of α-Fe was caused by the oxidation of powder, and it was confirmed that the oxygen content of the powder should be lower than 9000 ppm in order to prevent the α-Fe precipitation.
(3) The maximum coercivity of 2.24 MA·m−1 was obtained after the following condition; i.e., MG time: 108 ks, crystallization: at 1023 K for 1.8 ks, nitriding: at 723 K for 129.6 ks and annealing: at 623 K for 7.2 ks in N2.View full abstractDownload PDF (682K) -
Eiji Iwamura, Takashi Ohnishi, Kazuo Yoshikawa1995 Volume 59 Issue 6 Pages 673-678
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effects of Ta addition on the resistivity and hillock suppression were studied in Al-Ta sputtering films in comparison with Al-Cu alloy films. Ta was dissolved in the Al matrix of the as-deposited films. The metastable AlTa solid solution was decomposed into Al3Ta during annealing at more than 573 K. As the Ta content increased, the resistivity of the as-deposited films was increased, and the hillock density after annealing was remarkably reduced due to the increase of hillock formation temperature. The resistivity reduced after annealing due to decomposition of the metastable solid solution.
Resistivity and hillock suppression in the Al-Ta alloy films had stronger dependence on the content than the Al-Cu alloy films. It is probable that the dependence is attributed to the electric interaction between Ta and Al, and the suppression of the Al diffusion by the dissolved Ta.View full abstractDownload PDF (915K) -
Yasuharu Shirai, Masaru Sakamura, Itsurou Shishido, Masaharu Yamaguchi1995 Volume 59 Issue 6 Pages 679-680
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (167K)
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