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Volume 65, Issue 8
Displaying 1-15 of 15 articles from this issue
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Jyuniti Tanaka, Toru H. Okabe, Naohide Sakai, Tadashi Fujitani, Kazuhi ...2001 Volume 65 Issue 8 Pages 659-667
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSMetallic titanium has been produced by the Kroll process, in which titanium chloride is reduced by metallic magnesium. Although this process is a competent method to obtain high purity titanium, it is difficult to expect further improvement of productivity and also to recover excess heat evolved during the reaction. This is mainly because the product titanium by this reduction process is solid in sponge form, and difficult to recover continuously, and the process, has to be a batch type process. For developing a high speed continuous reduction process, various aspects were analyzed from the industrial point of view, and in this investigation, an attempt was made to produce titanium powder by utilizing a molten reaction media. It was already confirmed by preliminary laboratory-scale experiments that the titanium fine powder can be produced by injecting titanium tetrachloride into the reaction media, which is synthesized by indefinite mixture of molten magnesium chloride and liquid magnesium metal reductant. In this investigation, a bench scale reaction apparatus was newly constructed with the scope of scale up of the reduction process. Although the obtained titanium powder is contaminated by iron and oxygen, fine powder with 99% purity was successfully produced. Sintering examination of the power showed possibility for application to powder metallurgy.View full abstractDownload PDF (926K) -
Keiichi Ohya, Tomoyuki Inaba, Hiroshi Maeda, Mitsunori Sato2001 Volume 65 Issue 8 Pages 668-671
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe pellet samples with the nominal compositions of Bi1.8Pb0.4Sr2.0Ca2.1Cu3.0−XMXO10+δ (M=Fe and Co, x=0∼0.10) were prepared by the solid state reaction method, and the effect of Fe and Co substitution for Cu on the formation of Bi2223 phase and superconducting properties has been examined. The formation rate of Bi2223 phase strongly depends on the atmosphere (oxygen partial pressure) of the heat treatment, increasing with decreasing oxygen partial pressure down to 4%O2. Furthermore, the formation rate greatly decreases with increasing the Fe and Co substitution in 20%O2, and shows less dependency on the amount of the substitution in 4%O2. The critical temperature, Tc decreases linearly with increasing the Fe and Co substitution. This suggests that Fe and Co atoms are substituted for Cu site. The magnetization hysteresis width, ΔM and the irreversibility field, Hirr which are calculated from magnetic hysteresis curves at 77 K show the maximum at a Fe substitutive amount of 0.02. For the Co substitution, on the contrary, both ΔM and Hirr decrease greatly with increasing the substitution amount. The grain size of the samples scarcely depends on the amount of Fe and Co, showing almost the same size. These results suggest that some pinning centers are introduced into the Bi2223 crystals by the Fe substitution. Our present experiments did not elucidate the nature of the pinning centers.View full abstractDownload PDF (578K) -
Minoru Tagami, Keizo Kashihara, Tatsuya Okada, Fukuji Inoko2001 Volume 65 Issue 8 Pages 672-679
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESS99.99 mass% ⟨111⟩ aluminum single crystal specimens were deformed in tension to strains of about 20% at room- and liquid nitrogen(LN)-temperatures. Both specimens were annealed simultaneously at 773 K in an electric furnace until recrystallized grains were formed. At the same strain of 20% the flow stresses in the LN temperature and room temperature specimen were 238 MPa and 80 MPa, respectively. Its reason is due to the temperature dependence of cross slip. In neither specimen no deformation band was observed. The maximum misorientation among the cells measured by Electron Channelling Pattern(ECP) in the regions of the whole parallel-part of both specimens was only within 5°. The formation of recrystallized grains in ⟨111⟩ LN temperature specimen started earlier by 150 s at the same temperature of 773 K than that in ⟨111⟩ room temperature one. The rotation angles of the recrystallized grains to the orientation of the surrounding matrix about ⟨111⟩ axis normal to a common cross slip plane of the activated slip systems had approximately 15°∼50°. So these large rotation angles could not be explained from the “coalescence and rotation of cells” and “strain induced grain boundary migration” mechanisms. Probably the intersections of cell walls with very dense dislocation density (DDW), slip bands with heavy shear strain etc. would become nucleation sites of the recrystallized grains. Especially, the special intersections which have inverse rotation and large angle boundaries to the surrounding matrix should be chosen as the nucleation sites.View full abstractDownload PDF (2227K) -
Seiji Inaba, Shuhei Oda, Kenji Morinaga2001 Volume 65 Issue 8 Pages 680-687
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe thermal diffusivity and specific heat have been measured at room temperature by laser flash method and AC calorimetry, respectively. Thermal conductivity has been determined by the product of density, thermal diffusivity and specific heat. The Debye temperature data have been collected from the measurements of ultrasonic method. For the direct calculation of these properties from glass composition, empirical equations that consist of compositional parameters Vi and Gi were obtained, where Vi is the packing density parameter and Gi is the dissociation energy of a single component oxide, respectively. Experimental results indicate that the calculated values using our proposed equations are in a good agreement with the measured values in many glasses studied in this work.View full abstractDownload PDF (482K) -
Yuichiro Sudo, Kenji Yajima, Yoshiharu Mae, Shuichi Iwata2001 Volume 65 Issue 8 Pages 688-694
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSVarious copper alloys applied to electric and electronic use undergo the casting process as the first step of production. But a fully systematic investigation of their castability has not yet been attempted. In this work, liquidus gradients and solidification temperature ranges were acquired from phase diagrams of binary copper alloys and were arranged on the periodic table. As a result, it became clear that the liquidus gradients of the same group on the periodic table are almost constant, and elements that enlarge the solidification temperature range exist in the continuous areas around 2A and 6B groups on the periodic table. This result shows that these characteristics above mentioned seem to stem from the nature of the added elements and it is considered that they are also practically useful for estimating the castability of new alloys.View full abstractDownload PDF (458K) -
Ryoichi Monzen, Takayuki Kita, Kazuhisa Kita, Kenji Matsuda2001 Volume 65 Issue 8 Pages 695-700
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe effects of Be addition up to 0.1 mass% on the formation and growth of γ-Fe precipitates were examined for a Cu-1.0 mass%Fe alloy. The formation rate of precipitates increased with increasing solution temperature and Be content. The transition from growth to Ostwald ripening occurred more easily as the Be content increases. The rate of coarsening of precipitates decreased with increasing Be content because both the equilibrium solubility of Fe in the Cu matrix and the volume diffusion coefficient of Fe in Cu were reduced.View full abstractDownload PDF (421K) -
Tatsuya Ohmi, Yasuhiro Murota, Masayuki Kudoh2001 Volume 65 Issue 8 Pages 701-706
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe effects of some process conditions on the porosity of the NiAl castings produced by a centrifugal combustion synthesis has been investigated. In the centrifugal combustion synthesis experiments, a green compact of reactants consisting of Al, Ni and NiO was set in an alumina container in a centrifugal caster and was ignited to produce a molten NiAl by the following reaction:
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\ oindentAdiabatic combustion temperature of the reaction can be varied arbitrarily by changing the value of a. The molten NiAl was then solidified in the alumina container under centrifugal force. The porosity in the present study was designated by an area percent of macroscopic pores measured on the longitudinal cross section of the specimens. The results are summarized as follows: (1) The relative density of the green compact has no influence on the porosity of the cast NiAl. (2) The porosity decreases as the value a increases. (3) The application of centrifugal force is effective for the reduction of porosity.View full abstractDownload PDF (631K) -
Hiroyuki Mori, Kazuyuki Nakanishi, Hideo Tachikawa2001 Volume 65 Issue 8 Pages 707-713
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to improve the wear resistance of an aluminum alloy, plasma spraying has been carried out to 2017 aluminum alloy substrate by using high Si-Al alloy powders. In these high Si-Al coatings, Si particles with very fine sub microns grains were observed and the hardness of the coatings reached higher than HV200.
The tribological properties of high Si-Al coatings were studied using ball on disk test. The coatings were slid against the bearing steel (JIS SUJ2) balls to investigate fundamental friction and wear properties under unlubricated conditions.
The results showed that the wear resistance of high Si-Al coatings was much higher than that of A390 castings. The friction coefficient of the coatings ranged from 0.2 to 0.3, which was lower than that of A390 castings. The tribological properties of Al-40Si-Cu-Mg coatings were superior in these high Si-Al coatings, which promoted the formation of boundary film on the rubbed surface of the counter material by tribo-chemical reactions.View full abstractDownload PDF (1869K) -
Toshio Ishii, Masayuki Gonda2001 Volume 65 Issue 8 Pages 714-719
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSMicrostructure of a newly developed “long-tool-life” α-Al2O3 coated cutting tool and mechanism of epitaxial growth of the α-Al2O3 layer has been investigated. The tool was produced by coating cemented carbide chips with layers of a TiN layer, a Ti(C, N) layer, a bonding layer and an α-Al2O3 layer successively and in this order using the techniques of CVD. Cross section TEM analysis revealed the existence of a column in which α-Al2O3 grains had grown epitaxially around a protrusion formed around a {111} twin plane in the bonding layer twin which had in turn had grown in a similar way (epitaxially) on a surface of a Ti(C, N) twin, and also the surface of the protrusion is covered with steps on the atomic scale. In addition, SEM and TEM analysis on the surface of the bonding layer revealed that a protrusion had been formed with a vertical-plane shape along with a edge of a {111} twin plane on the surface of a bonding layer twin, and {211} planes of both the bonding layer twin and the protrusion are oriented in tangential directions to the substrate. As {211} planes of face-centered-cubic lattices in general are covered with steps on the atomic scale made up of {111} planes etc, and include the maximum allowed number of atoms on the cross-section of the {111} planes, it is reasonable to conclude that the steps covering the surface of the bonding layer may lead to promotion of the formation of the vertical-plane shape protrusions around the edge of the {111} twin planes through absorbing particles of the recant gases in CVD process at the corner of the steps, and also the steps covering the surface of the protrusion may promote the epitaxial growth of α-Al2O3.View full abstractDownload PDF (1470K) -
Masami Taguchi, Yuuki Hiramatsu, Tokiyoshi Hirasawa, Nobukazu Tanaka2001 Volume 65 Issue 8 Pages 720-725
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSSb-free alloys, especially Pb-Ca-Sn alloys are the choice material for the grids of the valve-regulated lead acid (VRLA) batteries. However, the grid is liable to be severely attacked, depending on the composition of the alloy. In this study, Pb-0.08 mass%Ca-Sn alloys with a wide range of Sn contents were prepared and the corrosion tests with charge/immersion cycling were carried out in 4.50 kmol m−3 H2SO4 at 348 K for 604.8 ks. The total mass change during the corrosion test, which is the sum of mass change of the sample electrode and amount of suspended powder in the solution, increases with decreasing of the Sn content. For the Pb-Ca-Sn alloys with 0∼0.20 mass%Sn, the amounts of the total mass change during the corrosion test with charge/immersion are about 8 times as much as those with immersion. A proportional correlation between the total mass change and Ca dissolution can be recognized during the corrosion test, with charge/immersion or with immersion. And, high Sn contents tend to coarsen the grain structures of the Pb-Ca-Sn alloy. These data suggest that the corrosion attack has mainly occurred at the grain boundary of the alloy. Moreover, the analysis of the charge reaction makes clear that about 97∼99% of the charge current is used for the oxygen evolution. Only 0.08∼2.75% of the current is spent in formation of the corrosion layer consisting of PbSO4 and β-PbO2 and the ratio decreases as the Sn content increases.View full abstractDownload PDF (745K) -
Effect of Pulse Current on the Oxide Layer during Pulse Current Pressure Sinteing of Aluminum PowderTakekazu Nagae, Masaru Yokota, Masateru Nose, Shogo Tomida, Takashi Ka ...2001 Volume 65 Issue 8 Pages 726-733
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe pulse current pressure sintering and hot press process were applied for sintering of aluminum powder produced by water and gas atomizing methods. The pulse current pressure sintering process could densify the water atomized powder in a short time compared with the hot pressing because it could remove the H2 gas at lower temperature. The gas prevents sintering of aluminum powder. The tensile strength of the pulse current pressure sintered gas atomized powder which contains low H2 was higher than that of hot pressed specimen. The electric resistivity of sintered specimens obtained by pulse current pressure sintering process was lower than that of hot pressed specimen. The oxide layer destruction was confirmed by this measurement of electric resistivity. The oxide layers were supposed to be fractured by the high temperature zone which was attributed to joule heat by the contact resistance.View full abstractDownload PDF (1219K) -
Masao Hayakawa, Saburo Matsuoka, Kaneaki Tsuzaki2001 Volume 65 Issue 8 Pages 734-741
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSMicrostructures of JIS-SCM440 steel tempered at 723 K were observed on an electropolished and a picric-acid etched surfaces by atomic force microscopy(AFM). At first, AFM image was taken on an electropolished surface. Carbides and blocks were clearly distinguished on the image, because the electropolishing rate depends on the crystal phase and its surface orientation. However, prior austenite grain boundaries could not be completely recognized. Secondly, AFM image was taken in the same area on a picric-acid etched surface. Prior austenite grain boundaries were observed, because the boundaries are preferentially etched. Thirdly, the both of AFM images were overlapped. This procedure gave us AFM image where prior austenite grain boundaries as well as carbides and blocks were clearly recognized. Finally, number and sizes of the carbides along prior austenite grain boundaries were examined.View full abstractDownload PDF (1499K) -
Shinji Itoh, Hitoshi Yamaguchi, Takashi Kimura, Toshiyuki Hobo, Takesh ...2001 Volume 65 Issue 8 Pages 742-746
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSWe examined the basic characteristics of the mass analysis method using DC helium glow discharge. As a result of investigating the relative intensities of the ions generated, we found that the ratios of doubly charged ions (He2+) and diatomic molecule ions (He2+) to He+ were 100:0.4:170. These ratios differed significantly from those in Ar glow discharge and thus indicated the generation of excessive He2+. We also detected up to He5+ of polyatomic ions. SEM observations of the discharge traces of He glow discharge and Ar glow discharge revealed that the trace of Ar glow discharge exhibited a rough and highly uneven surface as if the specimen had been peeled off. In contrast, trace of He glow discharge showed few irregularities, and specimen particles seemed to be removed as if a wall had collapsed. Furthermore, because He glow discharge produces a slower rate of spattering than Ar glow discharge, it took a long time (120 min or more) in the preliminary discharge to remove the stains from the surface. We found that the surface of the specimen must be cleaned in the preparation stage using a grinding method equivalent to buff grinding with alumina paste. While investigating the spectrum interference, we measured C at m⁄z13, which revealed the existence of interference by cluster molecular ions of 12C1H+ for up to 90 min after the start of discharge. The ion intensity ratios of light elements in He glow discharge were tens to hundreds of times greater than those in Ar glow discharge. The relative sensitivity factor of C (RSFC,Fe) obtained using a standard ferrous specimen was 0.263 in He glow discharge, but it was 3.309 in Ar glow discharge. We thus succeeded in achieving a high sensitivity to light elements.View full abstractDownload PDF (743K) -
Kazutoshi Nishimoto, Kazuyoshi Saida, Ryoichi Tsuduki2001 Volume 65 Issue 8 Pages 747-755
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to clarify the rapid densification behavior during pulsed electric-current sintering (PECS) bonding process, the kinetics of densification behaviors were investigated by comparing PECS bonding process with direct electric-current sintering (DECS) and hot pressing (HP) bonding processes. The ODS alloy powders of MA956 (Fe based alloy) and MA754 (Ni based alloy) were packed between bonding specimens as insert material. Bonding experiments showed that the completion time for fully densification in bonded interlayer on PECS bonding was about 1/2-1/3 times as short as those on DECS and HP bondings under the same conditions. The kinetics of the densification of bonded interlayer during all the three bonding processes could be expressed by a sequential kinetic equations of the grain boundary diffusion creep and volume diffusion. The densification rates controlled by creep were increased in order, PECS>DECS>HP. These results indicated that the rapid densification in PECS was attributed to the local rise in temperature on the neck region by Joule heat generation.View full abstractDownload PDF (1203K) -
Kazutoshi Nishimoto, Kazuyoshi Saida, Ryoichi Tsuduki2001 Volume 65 Issue 8 Pages 756-765
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to evaluate the mechanical properties of ODS superalloy joints bonded by pulsed electric-current sintering (PECS) technique, the tensile test at elevated temperature and creep rupture test were conducted for MA956 (Fe-based ODS alloy) and MA754 (Ni-based ODS alloy) joints. The ODS superalloys were bonded at 1323-1373 K for 0.9-64.8 ks in vacuum. The tensile properties at elevated temperature of completely densificated joints were almost comparable to those of base metal. However, the creep rupture lives of joints could be improved by the further holding at bonding temperature after the fully densification. The creep rupture lives of joint bonded for 64.8 ks reached about 70% of longitudinal directional life of base metal. TEM observations revealed that Cr2O3 inclusions existed on the prior particle boundary (PPB), and percentages of Cr2O3 inclusions on PPB were decreased with increasing the bonding time. The strengthen particles of oxide(Y2O3) were uniformly dispersed in the whole area of bonded interlayer without coagulating and coarsening. These results suggested that the improvement in creep rupture strength with bonding time was mainly attributed to the amelioration of the bonding strength of PPB.View full abstractDownload PDF (2029K)
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