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Volume 65, Issue 5
Displaying 1-23 of 23 articles from this issue
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Daisuke Shindo2001 Volume 65 Issue 5 Pages 331
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSDownload PDF (145K) -
Shunsuke Muto, Tetsuo Tanabe2001 Volume 65 Issue 5 Pages 332-337
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe principle, method and application of extended energy-loss fine structure (EXELFS) in electron energy-loss spectroscopy, which is effective in analyzing short-range structural correlations, are briefly described. Not only several issues peculiar to the EXELFS analysis are pointed out, but also a new method by applying a ‘wavelet transform’ is proposed. As an example of the EXELFS application, changes in the two- and three-body structural correlations in synchrotron X-ray irradiated amorphous silicon thin films are introduced.View full abstractDownload PDF (416K) -
Katsuhiro Sasaki, Susumu Tsukimoto, Minoru Konnno, Takeo Kamino, Hiroy ...2001 Volume 65 Issue 5 Pages 338-342
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSDynamic elemental mapping was carried out during an in-situ heating experiment in a transmission electron microscope using plasmon loss peaks in electron energy loss spectroscopy.
Migration of oxygen near an interface between Si and SiO2 during the reducing reaction SiO2→Si+O2 was studied by this method.View full abstractDownload PDF (1155K) -
Minghui Song, Kazutaka Mitsuishi, Hidehiro Yasuda, Kazuo Furuya2001 Volume 65 Issue 5 Pages 343-348
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSHigh-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS) and energy filtered imaging (EFI) were employed to characterize the structure of precipitates of Xe implanted in Al metal, as well as their structure change as a function of temperature ranging from 300 to 858 K. HRTEM observation revealed that crystalline and non-crystalline Xe precipitates coexist at room temperature. The critical size of precipitates between the crystalline and non-crystalline states is about 5.5 nm. In in-situ annealing, the crystalline precipitates start amorphization at 623 K and complete it at 773 K. Low energy loss peaks are recognized at 14.6 and 15.3 eV in the EELS at 300 K and 773 K, respectively. These peaks are considered to come from the Xe precipitates in Al. Energy shift of Xe-M4,5 edge to lower energy loss and an extra peak in Xe-M4,5 edge are detected in EELS at 300 K in connection with the crystallization of the Xe precipitates. However, the Xe-M4,5 edge becomes identical in position and shape at 773 K to that of gaseous Xe. It suggests that the Xe-precipitates exist in the gaseous state at 773 K.View full abstractDownload PDF (1854K) -
Hiroshi Tachikawa, Yasukazu Murakami, Takuya Ito, Yoh Iwasaki, Daisuke ...2001 Volume 65 Issue 5 Pages 349-355
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSMicrostructure of Co-CoO obliquely evaporated tape was studied by energy-filtered electron microscopy combined with high-resolution electron microscopy. Elemental mapping with electron energy-loss spectroscopy revealed that the specimen had a columnar internal structure, in which two types of columns, i.e. Co-rich and O-rich ones, were present. They were identified to be the columns containing mainly Co and CoO, respectively, by image processing of high-resolution electron microscope images. Although the size of Co particles was small, i.e. 5-20 nm, several particles gathered to form clusters within each Co-rich column. The c-axis of the particles inside the cluster was almost parallel to the longitudinal direction of the Co-rich column.View full abstractDownload PDF (2050K) -
Hidehiro Yoshida, Yuichi Ikuhara, Taketo Sakuma2001 Volume 65 Issue 5 Pages 356-360
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSHigh-temperature mechanical property in ceramics is directly related to the atomic structure and the chemical bonding strength in the grain boundaries. Transmission electron microscopy is a powerful tool to characterize the grain boundary structure. In this paper, the atomic structure and chemical bonding state at the grain boundaries in 0.05 mol%Lu2O3-doped Al2O3 polycrystalline, which shows an excellent high-temperature creep resistance, was investigated by high-resolution electron microscopy (HREM), energy dispersive X-ray spectroscopy (EDS), scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). In addition, a first principle molecular orbital calculation (MO) was made to examine the unoccupied density of states and chemical bonding state at the grain boundary.View full abstractDownload PDF (869K) -
Manabu Ishimaru, Tadakatsu Ohkubo, Yoshihiko Hirotsu2001 Volume 65 Issue 5 Pages 361-365
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSWe performed oxygen-ion-implantation into silicon carbide (SiC) to produce SiC-on-insulator structures. Single crystals of 6H-SiC (0001) wafer were implanted with 180 keV oxygen ions at 923 K to fluences ranging 0.2−1.4×1018 cm−2. Microstructures of the specimens were examined using cross-sectional transmission electron microscopy and scanning transmission electron microscopy (STEM) equipped with an energy dispersive X-ray spectrometer (EDXS) and an electron energy-loss spectrometer (EELS). A continuous buried amorphous layer is formed in specimens subjected to ion fluences ≥0.4×1018 cm−2. The amorphous structures change drastically between 0.7 and 1.4×1018 cm−2. STEM-EDXS/EELS measurements show that the sample irradiated to fluences of ≤0.7×1018 cm−2 possesses a buried amorphous SiCxOy layer, and oxygen concentration peaks around the center of the buried amorphous layer. On the other hand, a well-defined SiO2 layer including self-bonded carbon atoms is formed in the crystal irradiated to a fluence of 1.4×1018 cm−2, and this amorphous layer has a layered structure due to compositional variations of silicon, carbon, and oxygen. The formation of Si-O and C-C bondings is also confirmed by pair-correlation functions extracted from Fourier transformation of nano-beam electron diffraction patterns. These results indicate that the high-dose oxygen-ion-implantation is a viable means to produce SiC-on-insulator structures.View full abstractDownload PDF (828K) -
Naoko Kumagai, Hiroyuki Sasaki, Kazuhiko Kita, Junichi Nagahora, Akihi ...2001 Volume 65 Issue 5 Pages 366-373
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIt is expected that the electron-beam evaporation method can make alloys with excellent mechanical properties and new characteristics.
Al-based alloys with additions of Ti have been prepared by electron beam evaporation. The composition dependence of microstructures and mechanical properties have been studied by analysis transmission electron microscope.
In the Al-Ti alloy systems, up to Ti contents of 13 at%, the deposit consists of super-saturated solid solution of Al.
With increasing Ti content, the Vickers hardness of the deposits increases and the grain size becomes finer.
The Al-Ti alloy deposit annealed at 623 K exhibits the highest Vickers hardness with very fine microstructure of α-Al and Al3Ti(Ll2). As annealing at much higher temperature, the hardness becomes lower with microstructure of α-Al and Al3Ti(D022).View full abstractDownload PDF (1722K) -
Hajime Matsumoto, Eiichi Sukedai, Hiroyuki Yagi, Hatsujiro Hashimoto2001 Volume 65 Issue 5 Pages 374-381
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSAging behaviours of as-quenched ω-phase crystals (ωas-q) in a Ti-15 mass%Mo alloy were observed using in-situ dark field imaging technique and the relationship between ωas-q and aged ω-phase crystals (ωaged) was discussed. Due to heating to 423 K, about a half of ωas-q less than 2 nm was annihilated, but due to the subsequent aging at 423 K for 1.8 ks, ωaged appeared at the most of remained ωas-q with various sizes. It was found that ωas-q became the nucleation-site of ωaged. Compositions and lattice structures of ωas-q were investigated using EDS and HREM methods, and were also compared with those of ωaged. In the as-quenched alloy, no distinct difference was recognized between Mo contents of ωas-q and the matrix. This result suggests that ωas-q formed due to the displacement-type transformation. Linearity of rows and size homogeneity of lattice points of ωas-q were lower as compared with those of ωaged, and consequently these facts should be considered as one of the origins, which causes the difference of the physical properties such as ductility and electrical resistivity between as-quenched and aged Ti-Mo alloys with a certain range of Mo contents.View full abstractDownload PDF (2136K) -
Takeshi Fujita, Hatsuo Ikeda, Satoru Tanaka, Zenji Horita2001 Volume 65 Issue 5 Pages 382-388
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThis paper describes determination of the Ti-Al-Cr ternary phase diagrams using quantitative X-ray microanalysis in analytical electron microscopy. Alloys with several different compositions were subjected to heat treatments for equilibration at 1273 and 1473 K. Microstructural observations and selected area electron diffraction analyses were conducted for phase identification and characteristic X-rays were measured from each phase. The characteristic X-ray intensities were then converted to concentrations using the ζ-factor method while the absorption correction was simultaneously achieved with this method.
It was found that the three-phase regions such as α2+B2+γ, B2+γ+Laves and γ+Laves+L12 were present at 1273 K, whereas at 1473 K, no Laves phase was observed and disordering occurred from the α2 and B2 phases to the α and β phases, respectively. Thus, the three-phase regions were present as α+β+γ and β+γ+L12 at 1473 K. The α+β+γ and β+γ regions were extended to a lower Al concentration as the temperature decreases.View full abstractDownload PDF (1416K) -
Mitsuhiko Yoshida, Takashi Yaegashi, Yasukazu Murakami, Daisuke Shindo ...2001 Volume 65 Issue 5 Pages 389-396
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe phase diagram of Cr-rich portion of ternary Nb-Cr-Ti alloy system at 1523 K is investigated by means of X-ray diffraction, optical microscopy and analytical transmission electron microscopy.
In the region of single phase of (Nb, Ti)Cr2 intermetallics, Laves phase shows C36 dihexagonal structure in the Nb concentration between 0 mol%Nb and 4 mol%Nb. In the range of the Nb concentration more than 12 mol%Nb, Laves phase shows C15 face centered cubic structure. On the other hand, the region of duplex structure consisting of C36 and C15 phase is within the range of the Nb concentration between 4 mol%Nb and 12 mol%Nb. The solubility limit of Nb in Cr solid solution is as small as less than 0.5 mol%Nb. The maximum solubility limit of Cr in Laves phase equilibrated with Cr-b.c.c. solid solution is in a range of about 67∼69 mol%Cr depending on a content of Nb and Ti elements. The eutectic path on the Cr-rich portion of the ternary Nb-Cr-Ti alloy system lies in the Cr concentration line between 75 mol%Cr and 80 mol%Cr, and ends at the point of Nb concentration between 10 mol%Nb and 15 mol%Nb.View full abstractDownload PDF (1690K) -
Masaaki Sugiyama, Morihiro Okada, Yoshihisa Takada, Masayoshi Suehiro2001 Volume 65 Issue 5 Pages 397-403
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn the field of structural analysis of iron and steels, using an analytical transmission electron microscope equipped with a field emission electron gun, it becomes possible to investigate a segregation behavior at the specified interface, or a grain boundary in steels, which often play the important role of a starting point of non-uniform phenomena such as galvanizing, oxidation, and corrosion reactions. For this purpose, the focused ion beam fabrication method is a powerful technique to obtain a thin foil specimen from the specific region, but some disadvantages appear in the application to the sampling of steels with a magnetic body. They are represented by the magnetic disturbance and the occurrence of a ghost specific X-ray peak under the EDX analysis with a nano-probe electron beam. In the present research, the micro-sampling technique was employed to extract a steel sample with length of 10 μm order from the starting material in a range of mm size, with the results that those disadvantages were dissolved.
The technique was applied to make clear a formation mechanism of craters observed in a galvannealed steel. At the first, compositions of the Γ and δ phases were precisely identified, using a sample fabricated by FIB method. The scanning ion micrographs for the cross-section microstructure of a crater revealed that Γ-phase has not been formed at an interface between the galvanizing layer and a steel, and δ-phase still exists in the bottom of the crater. The Al segregation phenomenon with about 6 mass% is found at the interface between δ-phase and the steel. Based on these results, the formation mechanism of the crater is discussed on the retardation phenomenon of the galvannealing process.View full abstractDownload PDF (1613K) -
Susumu Ikeno, Hiroaki Matsui, Kenji Matsuda, Kiyoshi Terayama, Yasuhir ...2001 Volume 65 Issue 5 Pages 404-408
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSPrecipitation sequence in an Al-1.6 mass%Mg2Si alloy was investigated by DSC measurement and HRTEM observation. Four exothermic peaks (A, C, D and E) and one endothermic peak (B) were obtained when samples were heated at 10 K/min. Precipitates were confirmed when samples aged to the temperature of each peak were observed using HRTEM, and were classified into several types. Products in the region between peaks A and B were classified as GP zones. Precipitates between peaks B and C were classified as the random-type precipitates. Precipitates at peak C were classified as the parallelogram-type precipitates. Precipitates at peak D were classified as metastable phase β′. Precipitates at peak E were classified as equilibrium phase β. Although there have been many reports that the β″ phase is formed at peak C, this was not observed in the present study, rather random-type precipitates were observed. The hardness of samples heated to various temperatures was measured. The temperature that resulted in maximum hardness corresponded to the temperature that yielded the maximum amount of random-type precipitates.View full abstractDownload PDF (1204K) -
Kenji Matsuda, Hiroaki Matsui, Kiyoshi Terayama, Yasuhiro Uetani, Susu ...2001 Volume 65 Issue 5 Pages 409-413
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSDifferential scanning calorimetry (DSC) measurements and high resolution transmission electron microscope (HRTEM) observations were performed in order to confirm the precipitation sequence of Al-Mg2Si alloys containing of 0.6, 1.0 and 1.6 mass%Mg2Si during heating. Peaks in the DSC curves were clearly observed to form when the Mg2Si content was increased from 0.6 to 1.6 mass%. Exothermic peak A, endothermic peak B, and three exothermic peaks C, D and E appeared in the Al-1.0 mass%Mg2Si alloy upon heating from room temperature. Peak C was the highest exothermic peak among them. It was difficult to detect clear peaks in the DSC curve of the Al-0.6 mass%Mg2Si alloy. Needle-shaped precipitates were observed at 557 K, corresponding to peak C in the Al-1.0 mass%Mg2Si alloy, and coarsened with increasing temperature. There was far less precipitate in the Al-0.6 mass%Mg2Si alloy, and the precipitates were coarser. The highest density of random-type precipitate occurred in the temperature range of 493 K to 557 K in the Al-1.0 mass%Mg2Si alloy, as determined by HRTEM. Many parallelogram-type precipitates occur at 557 K, and the β′ phase appears at temperatures higher than 580 K. This tendency is similar to that of the Al-1.6 mass%Mg2Si alloy. The precipitation sequence in the Al-0.6 mass%Mg2Si alloy is similar to that in the Al-1.0 and 1.6 mass%Mg2Si alloys, however there is temperature range in the Al-0.6 mass%Mg2Si alloy where the abundance of parallelogram-type precipitate equals that of the β′ phase. No β″ phase was observed in any of the alloys. The hardness of alloys was greatest at temperatures corresponding to the respective peaks in the DSC curves in Al-1.0 and 1.6 mass%Mg2Si alloys, which is in agreement with the temperature at which the density of random-type precipitate is highest.View full abstractDownload PDF (1086K) -
Nobuo Tanaka, Satoshi Hata, Kensuke Oki, Noriyuki Kuwano2001 Volume 65 Issue 5 Pages 414-418
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSPartially ordered Ni4Mo alloys were observed for the first time at an atomic resolution with high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The Mo atomic columns in the D1a ordered structure were clearly visualized as bright square dots in the HAADF-STEM image. It was found that the ordered regions were observed with a high contrast in the defocus condition a little overfocused from the Scherzer defocus (Δf=\sqrtCS·λ) which is the condition for the smallest electron probe in STEM. The phenomenon was interpreted successfully by using the approximate imaging theory for HAADF-STEM proposed by Jesson et al. Using the present experimental and simulation results, an approximate imaging theory for visualizing short range ordered state in binary alloys, such as the Ni4Mo alloys, is proposed.View full abstractDownload PDF (1108K) -
Eiji Okunishi, Katsuhiko Ibe, Kazuhiro Hono2001 Volume 65 Issue 5 Pages 419-422
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe HAADF(High Angle Annular Dark Field) method and EDS(Energy Dispersive X-ray Spectrometer) analysis by the FE-STEM have been used in various research fields. The observation of the atomic level is possible by the high resolution Z-contrast image in the HAADF method. Recently, in the EDS system, the drift correction EDS mapping system was developed. And long time elemental mapping becomes possible by using this system and high-resolution two-dimensional elemental distribution images has come to obtained.
In this paper, The Plate like precipitate called Ω phase in Al alloy as analyzed by using those methods. As a result, The distribution of Ag in the interface between matrix and Ω phase were observed is smaller than 1 nm. Two-dimension distribution image of the atomic layer order was obtained by using those method.View full abstractDownload PDF (1009K) -
Sin Igarashi, Shunsuke Muto, Tetsuo Tanabe2001 Volume 65 Issue 5 Pages 423-426
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSWe demonstrate grazing incidence electron microscopy(GIEM) for observation of mesoscopical surface protrusions, such as blistering introduced by energetic gas ion implantation. This method enables us direct and nondestructive observation and characterization of surface protrusions without any modification of the microscope, when it is used in combination with associated analytical instruments. As an example, the surface blistering of single crystalline silicon was examined with the aid of the simultaneous application of electron energy-loss spectroscopy(EELS).View full abstractDownload PDF (543K) -
Ryota Uemichi, Yoichi Ikematsu, Daisuke Shindo2001 Volume 65 Issue 5 Pages 427-433
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSTo determine the mean free path (λp) for inelastic electron scattering of a silicon crystal at an accelerating voltage of 200 kV, precise measurements of the specimen thickness were carried out by convergent-beam electron diffraction (CBED) technique and electron energy-loss spectroscopy (EELS) using an analytical electron microscope. Through the evaluation of the specimen thickness by using CBED technique, it was found that precise measurements in the case of 400 reflection with convergent beam angle of 12 mrad were performed in the condition that the specimen thickness was set to be in the range of 100 to 500 nm. By subtracting the background in CBED patterns with an energy filter, minima and maxima of the intensity profile of the symmetric fringes in the diffraction disks were clearly observed. Consequently, it was clarified that the maximum thickness measurable for the 400 diffraction disks increased from 400 nm to 670 nm. Using the precise specimen thickness evaluated by CBED technique, λp with the collection semiangle 157 mrad was determined to be about 147±5 nm through EELS.View full abstractDownload PDF (793K) -
Testuo Oikawa, Chang-Woo Lee, Yukihito Kondo, Daisuke Shindo, Kijiro K ...2001 Volume 65 Issue 5 Pages 434-436
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSUnderstanding of electron beam broadening in specimens is important when analytical electron microscopy is carried out in the area of nanometer order with a fine electron probe. In this work, the electron beam broadening was experimentally measured for various specimens. For the specimens, amorphous SiO2, single crystal MgO and single crystal Si were used. The size of the beam diameter with and without the specimens was measured quantitatively by recording the intensity profiles accurately with an imaging plate system. As a result, the electron beam broadening was evaluated as a function of the specimen thickness, and it was compared and discussed with the values calculated on the basis of a theoretical model.View full abstractDownload PDF (340K) -
Hideyuki Ikeda, Hirohisa Masumoto, Hidehiko Matsuda2001 Volume 65 Issue 5 Pages 437-442
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSWe have studied the Kirkendall void formation in the diffusion bond between molybdenum and titanium by using the Monte Carlo method. When the ordering energy between vanadium and vacancy was a negative value, the addition of five atomic percent of vanadium to titanium suppressed the void formation for the diffusion bonds having a tendency to form the voids. On the other hand, a positive value of the ordering energy did not show any effects on suppressing the void formation. We found that the negative value of ordering energy generated the vanadium and vacancy complexes, and consequently prevented the void formation.View full abstractDownload PDF (560K) -
Yoshiyasu Itoh, Shoko Suyama, Takahiko Shindoh, Hideyasu Andoh2001 Volume 65 Issue 5 Pages 443-448
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe purpose of this study is to newly develop the coating process from a viewpoint of shot peening treatment. An experimental investigation was carried out for a shot coating of aluminum powder on four kinds of sintered-ceramics, such as zinc-oxide, zirconia, silicon nitride and silicon carbide. As a result, it made clear that the aluminum film could be formed by the shot coating at the surface of four kinds of sintered-ceramics. Namely, the shot coating consisted of the erosion process of ceramic substrate and the laying process of aluminum powder. Also, there was a tendency that the coating speed was increased with increasing the powder speed and preheat temperature of ceramic substrate and decreasing the thermal conductivity of ceramic substrate.View full abstractDownload PDF (1006K) -
Yoshiharu Doi, Kenji Matsuki, Hitoshi Akimoto, Tetsuo Aida, Shouichi O ...2001 Volume 65 Issue 5 Pages 449-457
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe fine grained Ni3Al (γ′)-NiAl (β) two-phase nickel aluminides reinforced with or without TiC particles were fabricated by a wet mechanical alloying and vacuum hot pressing process. The average grain sizes of the as-compacted intermetallics decreased from about 1.2 μm to about 0.4 μm with increasing in TiC volume fraction from 0% to 30%. High temperature compression tests for these intermetallics were carried out at a temperature in a range of 1073 K-1273 K and at an initial strain rate in a range of 1.4×10−4 s−1-5.6×10−2 s−1. Tensile tests were also performed at selected strain rates at 1273 K.
In the log true stress-log strain rate curves for the nickel aluminides containing TiC particles, two strain rate regions showing low and high strain rate sensitivity exponents, m, (region I and II, respectively) were recognized, while the intermetallic without TiC showed only region II in this compression condition. At strain rates higher than about 10−2 s−1 (region II) and at 1273 K, the value of m was larger than 0.32 for the nickel aluminides containing TiC particles. About 180% and 100% elongations were obtained for the nickel aluminides containing 0 and 10 vol.%TiC, respectively, at a condition of 4.2×10−2 s−1 and 1273 K. By the microstructure examinations using SEM and TEM, the occurrence of grain boundary sliding was observed in these nickel aluminides compressed at the strain rate of 1.4×10−2 s−1 and 1273 K.
The threshold stress, σth, estimated by using an extrapolation method increased with increasing in the TiC content. Each double logarithmic plot of the strain rate and the effective stress, σe(=σ-σth), can be approximated by a straight line with a slope of about 0.5 for the nickel aluminides containing TiC. This suggests that the superplasticity of the composites at the high strain rates can be explained by the grain boundary sliding model accommodated by dislocation slip.View full abstractDownload PDF (1569K) -
Tatsuya Ohmi, Yasuhiro Murota, Kazuhiko Kirihara, Masayuki Kudoh2001 Volume 65 Issue 5 Pages 458-463
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSCentrifugal precision casting of Ni-Al alloys produced by a thermite-type combustion synthesis has been examined. The compositions of the alloys were Ni-(25, 31, 37, 43 and 50) mol%Al. A graphite mold and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. The mold had a cylindrical cavity (15-mm diameter and 10-mm length) with a slender sprue (4-mm diameter). When the combustion synthesis reaction was induced in the centrifugal force field, the synthesized molten Ni-Al alloy flew into the mold. This process was successfully applied in casting the synthesized Ni-Al alloys. On the other hand, the alloys did not flow into the mold under 1G. The formation of pores in the centrifugally cast alloy varied depending on the alloy composition: (1) The Ni-25 mol%Al and Ni-31 mol%Al alloys had very little porosity. (2) The Ni-37 mol%Al alloy had numerous micropores. (3) The Ni-43 mol%Al and Ni-50 mol%Al alloys had many macroscopic pores.View full abstractDownload PDF (1160K)
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