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Volume 58, Issue 11
Displaying 1-17 of 17 articles from this issue
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Haruki Yamane, Yoshinori Maeno, Masanobu Kobayashi1994 Volume 58 Issue 11 Pages 1233-1238
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCo/Pd and Co/Au multilayered structures were determined from a comparison between X-ray scattering measurements and calculations. Particularly, the calculation model, in which a fluctuation of lattice spacings in the alloyed interlayers is taken into consideration, gives much better profile fittings than a fixed lattice spacing model. Multilayered structure was fabricated by a high quality periodicity, and scattering profile fittings revealed that the fluctuations of periodic thickness were less than 1 ML in both films. The fluctuation of periodic thickness ΔΛ was 0.105 nm in Co/Pd and 0.110 nm in Co/Au, where ΔΛ is a Gaussian distribution width of periodic thickness Λ. The fluctuation of periodic thickness was nearly the same for both films. On the other hand, the interlayer thickness was about 3.5 atomic layers in Co/Pd and about 2 atomic layers in Co/Au. The fact that Co/Au film has much steeper interface than Co/Pd is explained by considering that Au and Co are a eutectic system while Pd and Co are an isomorphous system.View full abstractDownload PDF (669K) -
Yoshihisa Harada, Yasufumi Funato, Masahiko Morinaga, Akihiro Ito, Yuj ...1994 Volume 58 Issue 11 Pages 1239-1247
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAlloying effects on the microstructures and solid solubilities have been investigated experimentally using alloyed MoSi2 specimens slowly cooled from 1473 K. It was found that alloying elements in MoSi2 were classified into three groups: (a) W and Re, both of them were mainly substituted for Mo atoms, and made a complete solid solution of MoSi2. (b) Cr, Zr, Nb, Ta and Al were soluble in MoSi2 to some extent, but the excess addition of them resulted in the formation of the second phase with a lamellar-like or a massive domain structure. The solubility limits of Cr, Zr, Nb and Ta were about 1.0 mol%, 1.1 mol%, 1.3 mol% and 5.0 mol%, respectively. Al was also soluble in MoSi2 up to about 3.0 mol%, but it was mainly substituted for Si atoms in MoSi2, in contrast to the substitutional behavior of the other alloying elements. (c) Ru and Hf were not soluble in MoSi2, but made the second phase with a lamellar-like structure. For example, the silicides, Ru2Si3 or HfSi2, were formed by the Ru or Hf addition. In addition, the eutectic phases appeared in the Al, Nb or Ta containing system. Furthermore, it was shown that the Vickers hardness increased largely by the addition of most soluble elements, due to the solid-solution hardening. However, the solid-solution softening was also observed in the case of Ta and Al additions.View full abstractDownload PDF (2109K) -
Katsutoshi Yamada, Syouichi Sekiguchi, Keizo Hashimoto1994 Volume 58 Issue 11 Pages 1248-1255
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effects of Mg and Si additions into the matrix on the tensile, bending and compressive strengths of the carbon fiber reinforced aluminium alloys (CFRM: PAN based high modulus CF, Vf=70%) fabricated by a pressure infiltration method have been studied.
The main results obtained are as follows.
(1) Mg addition up to 10 mass% to the Al matrix increases the bending strength up to 1250 MPa at about 8%Mg, but decreases the compressive strength to 600 MPa. The FRM with the matrix of Al-7.8%Mg alloy having a high bending strength of 1250 MPa and a low compressive strength of 600 MPa shows pull-out of the fibers on the fracture surface by SEM observation. No precipitates are observed by high resolution TEM in the interface between the fibers and matrix.
(2) Si addition of about 3% to the Al-Mg matrix makes a significant decrease in bending strength to 900 MPa and a small decrease in compressive strength to 500 MPa.
(3) Si addition up to 12 mass% to Al matrix makes a small increase in bending strength to 600 MPa and a significant decrease in compressive strength to a level lower than 500 MPa.
(4) Mg addition of about 1% to the Al-Si alloy matrix makes a significant increase in compressive strength up to 1000 MPa at about 7%Si, without changing of the bending strength. The FRM with the matrix of Al-7.1%Si-0.36%Mg alloy having a low bending strength of 600 MPa and a high compressive strength of 1000 MPa exhibits flat fracture like shear mode for bending test. High resolution TEM work identifies the Al4C3 precipitates on the interface.
(5) Tensile strength and bending strength have a relationship based on our results using thin bending specimen. Therefore, we regarded the bending strength as the substitute of the tensile strength.View full abstractDownload PDF (1634K) -
Byung-Nam Kim, Teruo Kishi1994 Volume 58 Issue 11 Pages 1256-1262
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA crack deflection model reported previously to explain fracture behavior of ideal polycrystalline materials, is applied to analyze fracture behavior of Al2O3 polycrystals. For anisotropic effects within a grain, the experimental results on single crystal Al2O3 are used, and crack propagation through a grain is considered. The calculated fracture toughness and propagation angle when a crack propagates in an anisotropic single crystal are combined with the crack deflection model. As a result, the fracture toughness, transgranular fracture ratio and distribution of crack propagation angle are calculated as a function of grain boundary toughness.
The maximum fracture toughness obtainable in the equiaxed Al2O3 polycrystals is estimated to be about 4.8 MPa\sqrtm which is about 3 times that of single crystals, when the grain boundary toughness is 1.4 MPa\sqrtm. The primary reason for the increased toughness of polycrystals over that of single crystals is attributed to crack path restriction at triple and quadruple points. The predicted theoretical relationship between fracture toughness and transgranular fracture ratio showed good agreement with the experimental results. Also the predictions for the distribution of crack propagation angle are consistent well with the experiments.View full abstractDownload PDF (1284K) -
Kazuwo Imai1994 Volume 58 Issue 11 Pages 1263-1270
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBasic equations (BE) in the title are derived, whose main characteristics are as follows. (1) Plastic deformation of the single-crystal specimens is due to slip on N slip systems, where N is an arbitrary positive integer. (2) The major part of the BE is composed of simultaneous differential equations. By the BE, the tensile stress, the resolved shear stresses (RSS), the unloaded specimen length, and crystal-orientation factors are related to controlled or measured variables mentioned below, and to deformation-state variables such as the slip strain rates on the N active slip systems. (3) The BE are derived for two types of tensile tests; one is the test in which the extension rate (crosshead speed) is controlled and the load is measured, while the other is the test in which the load is controlled and the crystal specimen length is measured. (4) In the derivation of the BE, the deformation gradient tensor of the crystals is decomposed into plastic and elastic parts. The decomposition can be uniquely defined using base vectors of material coordinates and those of lattice coordinates. (5) The single-crystal test-pieces consist of the central parts (specimens) and the end parts; the former are assumed to be stressed uniformly and undergo homogeneous elastic plastic deformation, while the latter and the testing machines are assumed to deform elastically. The BE include Young’s modulus and Poisson’s ratio of the specimens and a combined modulus of the end part-machine system. (6) The BE are necessary for computer simulations of tensile tests of single crystals. Methods for comparing the computed results with experimental ones in respect of RSS-slip strain behavior on the primary slip systems are discussed.View full abstractDownload PDF (1005K) -
Sumiko Sanuki, Akio Sugiyama, Minoru Tunekawa, Kiyotaka Kadomachi, Koi ...1994 Volume 58 Issue 11 Pages 1271-1278
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA precipitation stripping reaction of fine Sm2(C2O4)3·10H2O crystals from an organic solution containing the acidic extractant such as VA10 and D2EHPA by using an aqueous oxalic acid solution was investigated to provide the basis of a novel hydrometallurgical route for the recovery of metal values from scrap Sm-Co permanent magnets.
It was found that Sm2(C2O4)3·10H2O can be readily crystallized by stripping Sm(III)-loaded organics containing the acidic extractant by using an aqueous oxalic acid solution. The percent recovery of samarium oxalate from the organic phases containing VA10 or D2EHPA increases with the increase in oxalic acid concentration. Although the precipitation stripping reaction of samarium oxalate from Sm(III)-loaded VA10 takes place quantitatively, the excess amount of oxalic acid is required to recover samarium oxalate crystallines from Sm(III)-loaded D2EHPA. The concentration of Sm(III) and extractant in the organic phase and that of acid added to the stripping solution to adjust its pH value had little effect on the stripping reaction from Sm(III)-loaded VA10, whereas the percent recovery of samarium oxalate from D2EHPA extracted Sm(III) was considerably influenced by those factors. Although the size of needle-like crystallines recovered from the former organics is 1∼5 μm in length, that from the latter organics is slightly larger.View full abstractDownload PDF (896K) -
Sumiko Sanuki, Akio Sugiyama, Kazuhiro Takata, Koichi Arai1994 Volume 58 Issue 11 Pages 1279-1287
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe applicability of reductive stripping technique for the preparation of fine particles of Pt and Pd from Pt(II), Pt(IV) and Pd(II)-loaded Organics was investigated. Pt(II), Pt(IV) and Pd(II)-loaded Organics were prepared by extracting the chloro-complex solutions of those metals with TBP or Alamine 336. It was found that the precipitation of those metals from the organic phase containing TBP can be achieved by stripping with an aqueous alkaline solution of NaBH4, yielding around 1 μm powders. Side reaction of the reductive stripping is an acid decomposition of NaBH4, and incidently the excess amount of NaBH4 is required to complete the reductive stripping reaction.
The important parameters to suppress the side reaction are the NaOH concentration in the stripping solution and VO⁄VW ratio. Under the experimental conditions employed in this study, it was unable to reduce Pt(II) or Pt(IV)-loaded Alamine 336 organics as far as NaBH4 was used as a reductant.View full abstractDownload PDF (1482K) -
Satoshi Itoh, Takeshi Azakami1994 Volume 58 Issue 11 Pages 1288-1293
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe Zn-Fe-O system can be divided thermodynamically into three regions: (i) Fe-Zn-ZnO-FeO system, (ii) FeO-ZnO-ZnFe2O4-Fe3O4 system and (iii) Fe3O4-ZnFe2O4-Fe2O3 system. Phase relations in each system have been studied at 1200 K by equilibrating synthetic samples in evacuated sealed quartz tubes. The results indicate that the phase relations at 1200 K are almost the same as that at 1100 K, while the mutual solid solubilities at 1200 K between ZnO and FeO are slightly larger than that at 1100 K. On the basis of the results and the previous data concerning the EMF using a stabilized zirconium oxide solid electrolyte, the equilibrium partial pressures of oxygen, −logpO2(=−log(PO2⁄P\ominus)), at 1200 K were thus estimated as follows: 20-16 for region (i), 14-12 for region (ii) and 6-3 for region (iii), respectively.
The activities of the components in Fe-Zn, FeO-ZnO and Fe3O4-ZnFe2O4 systems were then obtained by applying the Gibbs-Duhem relation in each region.View full abstractDownload PDF (618K) -
Hidehiko Kamide, Hiroyasu Sato, Yuichi Tanaka1994 Volume 58 Issue 11 Pages 1294-1298
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSStress corrosion cracking tests were done on surface modified 304 stainless steels in a 2.5 kmol/m3 H2SO4-0.4 kmol/m3 NaCl sloution in order to know the effect of treatments by diffusion coating (Si, Ti and Al), plating (Cr and Ni) and the combination of these methods on the SCC susceptibility in the solution.
The time to failures of Cr-plated specimens and Cr plated specimens after Si diffusion coating were prolonged by 3 to 4 times compared with that of 304 stainless steel under an applied stress of 90% of 0.2% proof stress. The time to failure of the Cr-plated specimen after Ni plating increased with increasing diffusion time at 1373 K and the SCC susceptibility of the specimen diffusion-treated for 14.4 ks was improved by 1 order compared with that of 304 stainless steel under an applied stress over the proof stress. The corrosion rate of the Ni-plated specimen was remarkably suppressed but the initiation of intergranular corrosion under an applied stress accelerated the SCC. Such intergranular corrosion of Ni-plated specimen was controlled by the combination of Cr plating and the diffusion treatment at 1373 K. The composition of the specimen in the middle of the diffusion layer corresponded to that of the high Ni stable austenitic phase.
It is thought that the surface modification of 304 stainless steel for the inhibition of SCC in a H2SO4-NaCl solution depends largely on the improvement in corrosion resistance and the composition of a stable austenitic phase.View full abstractDownload PDF (1273K) -
Masayuki Itagaki, Roland Oltra1994 Volume 58 Issue 11 Pages 1299-1303
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe laser impact technique has been applied to the activation of passivated iron for the investigation of the repassivation kinetics combined with a channel flow double electrode (CFDE). The amount of ferrous ion dissolved from the activated iron electrode during repassivation was detected with the CFDE system. The total charge for repassivation, Qw, was separated into the partial charges for dissolution of ferrous ion, Qdiss, and formation of adsorbed species, Qf. The Qdiss decreases with increasing electrode potential. On the other hand, the Qf does not depend on the electrode potential, and its value corresponds to the formation of a monolayer of trivalent oxide film. The numerical simulations for repassivation of iron were performed under a reaction model involving two adsorbed species, and their results were in good agreement with the experimental ones. The actual repassivation rate was characterized by the surface coverage of passivating adsorbed species, θ2(t).View full abstractDownload PDF (430K) -
Takehiko Mae, Masao Ihara, Hideo Iotake, Seiichi Toriyama, Satoshi Sun ...1994 Volume 58 Issue 11 Pages 1304-1310
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe degradation of corrosion resistance for Al-9 mass%Mg alloys with Ga is investigated by the measurements of anodic polarization curves, potentiostatic dissolution tests, immersed corrosion tests and scanning electron microscopic observation of corroded surfaces of the alloys with a supersaturated solid solution phase in dilute HClO4 solutions.
The main results obtained from the experiments are summarized as follows:
(1) The activation potentials (Eactive) of Al-9 mass%Mg alloys with a supersaturated solid solution phase in a dilute HClO4 solution decreases with increasing Ga content in the alloys and the solution temperature. Therefore, the corrosion resistance of the alloys decreases with increasing Ga content in the alloys and solution temperature. The corrosion of the alloys is uniform despite of the specimens used at the supersaturated solid solution phase.
(2) The corrosion behavior of Al-9 mass%Mg alloys in dilute HClO4 solutions may be divided into two potential regions: The oxide film is formed on the corroded surfaces of the alloys, and the anodic dissolution rates decreased at the potentials below Eactive. On the other hand, the anodic dissolution rates increase with increasing concentration of HClO4, solution temperature and Ga content in the alloys at the potentials higher than Eactive. The corrosion of the alloys containing Ga is enhanced by the selective dissolution of Mg or Al from the matrix of the alloys.View full abstractDownload PDF (2002K) -
Tatsuya Ohmi, Kouki Minoguchi, Masayuki Kudoh, Youichi Itoh, Kiyotaka ...1994 Volume 58 Issue 11 Pages 1311-1317
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe hypereutectic Al-Si alloy slurries with various mean sizes of primary silicon crystals were produced by the slurry-melt mixing process, in which the hypoeutectic alloy slurry and the hypereutectic alloy melt with various silicon contents were mixed and cooled under different environmental conditions. Two kinds of parameters were examined to evaluate the effect of the combination of the alloy composition on the primary silicon crystal size: one is related to the stability of the primary silicon crystals in the mixed alloy, and the other to the number of them which are to nucleate in the second alloy. It was elucidated that both of them provide a good guide on controlling the primary silicon crystal size. And it was also observed that the heat absorptivity of the mixing vessel plays a more important role in the refinement of the primary silicon crystals than the thermal condition of the atmosphere.View full abstractDownload PDF (833K) -
Masamichi Udaka, Kazuhiro Kawasaki, Takao Yamazaki, Minoru Umemoto, Is ...1994 Volume 58 Issue 11 Pages 1318-1326
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCu and Ni ultrafine-particles (UFP) with a surface mean diameter of 90 nm were produced using direct current thermal plasma. These UFPs were subjected to either pressurized or nonpressurized sintering to produce sintered compacts with a ultrafine microstructure. The sintering behavior of UFP and characteristics of sintering were examined. To maintain the surface activity, these UFPs were collected and compacted in a glove box, the inside of which was controlled to be an Ar atmosphere with a substantially small content of O2 and H2O.
The results obtained were as follows: (1) As synthesized UFPs can be densified at a lower temperature than the conventional powder because of their high surface activity. In the case of nonpressurized sintering, the lowest temperature to produce essentially fully dense compacts is 573 K for Cu and 673 K for Ni, while in the case of pressurized sintering, it is 423 K for Cu and 500 K for Ni. (2) The sintered compacts thus obatined have a submicronsized microstructure and the Hall-Petch type relationship holds between the grain size and hardness. (3) The low sintering temperature for the dense compacts observed in UFP could be explained reasonably by considering the influence of surface energy on the boundary diffusion mechanism of sintering. (4) The sintering rate was found to be more sensitive to the particle size than the grain growth rate. Because of such a difference in the dependence of particle size, sintering of UFP can be completed without grain growth and a submicronsized microstructure can be obtained.View full abstractDownload PDF (1967K) -
Yutaka Yanaba, Koji Hayashi1994 Volume 58 Issue 11 Pages 1327-1330
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn our previous study on the flexural strength (σm) of Si3N4-base ceramics, it was found that the number of fragments (Nf) of the broken test piece increased with increasing σm, and the analysis of this phenomenon suggested that Nf had a correlation with the fracture toughness (KIC). In this study, we examined first whether such a correlation between Nf and σm is found for WC-10 mass%Co cemented carbides which has higher KIC than Si3N4-base ceramics, and second whether a correlation is observed between the total macroscopic area of fracture surfaces (Smf) and σm for both specimens, and third whether a correlation is observed between the dependence of Smf on σm and KIC.
The results obtained were as follows. (1) A positive correlation was found between Nf and σm, also for the cemented carbides. Between Smf and σm, a more strong positive correlation was observed for both specimens. The σm at a given Nf or a given Smf was higher in the cemented carbides than the Si3N4. (2) Taking into consideration the microscopic and macroscopic energy balance in the propagation of cracks or the formation of fracture surfaces, the equation of σm=ψ·KIC·Smf1⁄2(ψ was a shape factor) was derived for general hard materials. In fact, it was confirmed for both specimens that σm was proportional to Smf1⁄2. And the ratio (3.9) of the slopes of two regression lines for both specimens coincided well with the ratio (3.7) of KIC which was obtained by SEPB method. (3) There is a possibility that the KIC of a hard material can be estimated in general from its σm−Smf1⁄2 relation, by using the σm−Smf1⁄2 relation and KIC of above two kinds of hard materials.View full abstractDownload PDF (391K) -
Gil Geun Lee, Hitoshi Hashimoto, Ryuzo Watanabe1994 Volume 58 Issue 11 Pages 1331-1336
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTumbler ball milling experiment on Cu powder was carried out to investigate powder adhesion on ball surfaces and the mill container wall during the mechanical alloying of ductile metal powders. The weight ratio of the adhered powder to an initial powder filling was measured with milling time of up to 40 h as functions of ball filling ratio and powder filling ratio. The motion of milling balls was observed through a transparent end wall of the mill container to study the role of ball motion in the powder adhesion.
With an increase in the ball filling ratio from 10 to 50%, the adhesion weight ratio increases and then decreases drastically at 60%. This change in the adhesion weight ratio with ball filling ratio corresponds well to the moment of working ball bed around the center of rotation of the mill container, where moment is regarded as the energy accumulated in the moving ball bed. The adhesion weight ratio decreased with increasing powder filling ratio and it is found that the adhesion weight ratio is proportional to the effective specific milling time. We present a microforging analysis on adhesion for the milled powder particles in equiaxed shape which were cold-welded on the ball surfaces and container wall and microforged into thin adhesion layers by the impacting action of the balls.View full abstractDownload PDF (666K) -
Masahiro Fukumoto, Syogo Itoh, Isao Okane1994 Volume 58 Issue 11 Pages 1337-1342
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe RF thermal plasma nitriding process of a Ti alloy was fundamentally investigated. Based on the results obtained in the nitriding process, reaction plasma spraying was carried out to fabricate the nitride coating.
The results obtained are summarized as follows:
1) As a result of RF thermal plasma nitriding of the Ti alloy, the TiN surface layer, followed by the TiN, Ti2N and Ti mixed layers in the order of depth direction, was observed on the surface region of the alloy substrate.
2) A linear relationship was recognized in the relation between the thickness of the nitride layer and the square root of treatment time. Therfore, the thermal plasma process seemed to be a diffusion dominating process. From the comparison of the nitride layer thickness under the same conditions of substrate temperature, the effect of hydrogen addition on nitrogen was investigated.
3) The diffusion rate of nitrogen in the Ti alloy substrate: Rd was estimated from the experimental results obtained, and the plasma spraying of Ti powder was conducted under the deposition rate of less than Rd. Consequently, the possibility of the reaction plasma spraying was found in the present study.View full abstractDownload PDF (828K) -
Manabu Tanaka1994 Volume 58 Issue 11 Pages 1343-1348
Published: 1994
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effects of the amount of cold work on the fractal dimension of grain boundary were investigated using specimens of the commercial pure iron cold-upsetted in the range from 0% to about 85%. The fractal dimension of grain boundary was estimated principally by approximating the length of the grain perimeter (the length of grain boundaries which belonged to a grain) by line segments.
The length of the grain perimeter, L, in each specimen decreased with an increase of the scale of the analysis, r, in the range from about 5×10−7m to about 3×10−6m (region I) and above about 1×10−5m (region III) of r, while it showed a constant value, Lp, between about 3×10−6m and about 1×10−5 m of r. Total datum points of several grains were unified by dividing L by Lp and by plotting L⁄Lp against r. The fractal dimension of grain boundary was obtained by using the datum points in region I, since the change in the grain-boundary configuration with cold work was associated with the slip in the grains. The fractal dimension of grain boundary increased from about 1.05 to about 1.15 with increasing amount of cold work in the range from 0% to about 50% of cold reduction, but it was almost constant above 50% cold work. The box-counting method gave a little larger values of the fractal dimension of grain boundary than the coarse-graining using line segments. The shape change of grains with cold work was also examined and interpreted by a simple analysis in this study.View full abstractDownload PDF (915K)
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