Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 60 , Issue 10
Showing 1-18 articles out of 18 articles from the selected issue
  • Kazuo Kasahara, Yuji Ikeda, Takashi Kimura, Tokuzou Tsujimoto
    1996 Volume 60 Issue 10 Pages 907-913
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Oxidation behavior of the intermetallic compound TiAl with additions of Y and REM (Ce, Nd, Sm, Tb, Dy) as third elements has been investigated at 1173 K in air by means of cyclic oxidation tests.
    A small amount of Y addition restrains surface segregation of S and is effective for reducing spalling and breaking of oxide scale. The addition of a large amount of Y (2 mol%), however, increases an invasion of oxygen, and accordingly the mass gain by oxidation increases.
    The addition of REM also restrains surface segregation of S, and leads to suppression of breaking and spalling of oxide scale, then the oxidation resistance is improved. However, the effect of REM addition to TiAl alloys is not so remarkable as that to Fe- and Ni-base alloys. This fact suggests that the scale spalling on TiAl-base alloys is controlled not only by S segregated at the scale-alloy interface, but also by other several factors
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  • Hideo Saito, Minoru Mori, Yoichi Ishida
    1996 Volume 60 Issue 10 Pages 914-920
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The behavior of hydrogen trapping sites in an austenitic stainless steel SUS316L exposed at 253 K was investigated by tritium transmission electron microscopic autoradiography. From the analysis of diffraction pattern and the orientation relationships between the grain boundaries the predominant tritium trapping sites are found at the grain boundaries with index number planes of high order than those with index numbers of low order. The length of hydrogen trapping sites the plane defects on the grain boundaries was about 3.23 μm. The number of the blackened silver particles was about 32 pieces. The tritium trapping sites exposed at 253 K were observed at precipitates (Cr23C6) and plane defects structure on the grain boundaries, in the vicinity of the triple points, at facet corners of twins, dislocations, and interfaces between precipitates and the matrix plane.
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  • Yoshio Kawamura, Atsuo Gyobu, Hiroshi Horikawa, Toshio Saburi
    1996 Volume 60 Issue 10 Pages 921-927
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Ti-Ni alloy films were deposited on quartz substrates by sputtering in argon atmosphere, using a sputtering target of an equiatomic TiNi alloy. The composition of the films were determined by electron probe micro-analysis using a calibration line prepared from bulk samples of well-established compositions. Since it was found that the Ti content in a deposited film was less than that of the target material, the film composition was controlled by placing Ti pieces on the target and changing their sizes. In this way it was successful in obtaining films with various compositions. Transmission electron microscope observation showed that the as-deposited films are amorphous when the substrate temperature is kept below 423 K during sputtering, and that they are crystallized when the specimens are heated above 708 K. By the heat treatment at temperatures above 708 K, Ti2Ni precipitated in the Ti-46.8 at.%Ni and Ti-48.4 at.%Ni films, and Ti3Ni4 precipitated in the Ti-51.4 at.%Ni film, but no precipitation occurred in the Ti-50.0 at.%Ni film. The martensitic transformation in these films were investigated by differential scanning calorimetry and electron microscopy. The R-phase transformation occurred reversibly on cooling and heating the films in the electron microscope. It was confirmed by constant load thermal cycling tests that the films show very good shape memory.
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  • Hideshi Nakatsu, Takeshi Miyata, Setsuo Takaki
    1996 Volume 60 Issue 10 Pages 928-935
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    In an Fe-22 mass%Mn alloy which undergoes the athermal transformation from austenite(γ) to epsilon martensite(ε), the effects of the γ grain size on the γ→ε transformation and the mechanical properties of (γ+ε) structures have been investigated by means of optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analysis. The γ grain size was altered from 10 to 100 μm by recrystallization. With grain refining, the formation of ε is suppressed and both of the elongation and the ultimate tensile strength are greatly enlarged. The 0.2% proof stress, however, does not depend on the γ grain size, because the yield stress is determined by the onset of γ→ε stress-induced transformation.
    The fracture modes of this alloy depend on the microstructures of ε plates. When the γ grain size is as large as 100 μm, a significant stress concentration takes place at the intersections of ε plates within γ grains during the deformation. Such a stress concentration causes a microcrack initiation at the intersections of ε plates and this leads to the onset of quasi-cleavage fracture along thick athermal ε plates. When the γ grain size is refined to 10 μm, however, the quasi-cleavage fracture is completely suppressed because ε plates become difficult to intersect each other within small γ grains. Consequently, γ grain refining gives favorable effects as follows: (1) change in the morphology of athermal ε, (2) reduction in the stress concentration at grain boundaries, and (3) uniform dispersion of deformation strain. In terms of the suppression of quasi-cleavage fracture by γ grain refining, the effect (1) is a most contributory factor in the Fe-22 mass%Mn alloy.
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  • Hideshi Nakatsu, Takeshi Miyata, Setsuo Takaki
    1996 Volume 60 Issue 10 Pages 936-943
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    In an Fe-27 mass%Mn alloy, which has a fully austenitic structure at room temperature and undergoes deformation-induced transformation from austenite (γ) to epsilon martensite (ε), the effects of γ grain size on the deformation-induced ε transformation and mechanical properties have been investigated by means of optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. The mean γ grain size was controlled to be between 10 and 100 μm by a recrystallization method. With grain refining, the formation of ε is suppressed and mechanical properties are improved.
    When the size of γ grains is as large as 100 μm, very thin ε plates form in the early stage of tensile deformation. But when refined to around 10 μm, they do not form during the deformation up to the true strain of 0.1 but only the dislocation density increases. For the formation of deformation induced ε, a lot of partial dislocations have to move on {111}γ planes closely. In the alloy with fine γ grains, however, the number of dislocations which can be piled up on each {111}γ plane is decreased by grain-refining, so that a secondary slip system acts prior to the formation of ε plates. This is the reason why the deformation induced ε transformation is suppressed by grain-refining.
    Moreover, in the alloy with large γ grains, a significant stress concentration takes place at grain boundaries on which deformation induced ε plates impinge, and this results in the onset of a quasi-cleavage fracture attributed in grain boundary exfoliation. Austenite grain refining gives the favorable effect as follows: 1) reducing the stress concentration at grain boundaries, 2) uniform dispersion of deformation strain, thus this quasi-cleavage fracture is completely suppressed by the grain-refining to 10 μm.
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  • Kei Ameyama, Mitsuya Hashii, Nobuyuki Imai, Toshinori Fujii, Nobuyuki ...
    1996 Volume 60 Issue 10 Pages 944-951
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The effect of hot isostatic pressing (HIP) temperature on the microstructure and mechanical properties of Ti-48 mol%Al-1 mol%Mn compacts fabricated by mechanical alloying was investigated. N-heptane was used as a process control agent for the mechanical alloying. The compacts HIP treated at 1173, 1373 or 1573 K showed an ultra-fine equiaxed grain structure, i.e., a microduplex structure, consisting of TiAl (γ) and Ti2AlC phases, and their average grain sizes were 185 nm, 510 nm and 1.5 μm, respectively. The γ phase was considered to be formed by an α→γ massive transformation during heating. On the other hand, the compacts HIP treated at 1623 or 1673 K showed quite different microstructures from the above HIP compacts. The 1623 K-HIP compact was composed of equiaxed γ grains, whose size was approximately 11.5 μm, rectangular shaped Ti2AlC particles, and a small amount of the grain boundary nucleated α phase. Although the 1673 K-HIP compact showed a microstructure similar to the 1623 K-HIP compact, the γ grains were coarsened to be approximately 27.8 μm in diameter and the Ti2AlC particles were more elongated rectangles. Furthermore, the amount of the grain boundary nucleated α phase was increased and the lamella α phase nucleated at γ twin boundaries was observed in the 1673 K-HIP compact. Mechanical properties determined by compressive testing at various temperatures made clear that the compacts HIP treated at 1173, 1373 or 1573 K have good workability at elevated temperatures and those HIP treated at 1623 or 1673 K have good high temperature strength. These mechanical properties were influenced significantly by the microstructure, especially by the grain size and morphology of the Ti2AlC phase.
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  • Satoru Kenjo, Yoichi Nishino, Shigeru Asano
    1996 Volume 60 Issue 10 Pages 952-956
    Published: 1996
    Released: April 04, 2008
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    Amplitude-dependent internal friction in aluminum films on oxidized silicon substrates has been investigated by the free-decay method of resonant flexural vibration. According to the constitutive equation, the internal friction in aluminum films can be evaluated separately from the measured data on the film/substrate composites. The internal friction in aluminum films is considerably reduced after heat treatment between 620 and 720 K. In the annealed state, the amplitude-independent part decreases as the film thickness decreases, while the amplitude-dependent part shifts to a higher strain. On the basis of the microplasticity theory, the amplitude-dependent internal friction can be converted into the plastic strain as a function of effective stress. The stress-strain responses thus obtained for aluminum films show that the plastic strain of about 0.01% of the total strain increases nonlinearly with increasing stress. These curves tend to shift to a higher stress with decreasing film thickness. It is found that the microflow stress is inversely proportional to the film thickness, provided the grain size is larger than the film thickness.
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  • Akira Kasahara, Hiroaki Nakamura, Youichi Ogawa, Yosihiko Isida, Kazuy ...
    1996 Volume 60 Issue 10 Pages 957-961
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Crystallization of a glass with the composition of 33.9Li2O-33.9B2O3-29Li2SO4-3.2Al2O3 was investigated by DTA and Dilatation methods. The electrical conductivity of the crystalline glass and the electromotive force (EMF) of the concentration cell made with the crystalline glass as the solid electrolyte were measured.
    The results indicate that the glass-transition temperature is 650 K and the softening temperature of the crystalline glass is higher than 971 K.
    The temperature dependencies of the specific conductivity are expressed as follows;
    (This article is not displayable. Please see full text pdf.)
    \ oindentand their apparent activation energies for conduction are 100.8 kJ mol−1(593∼833 K) and 35.9 kJ mol−1(833∼943 K).
    The concentration cells showed a stable Nernstian EMF corresponding to the partial pressure of SO2 in a range of 43-800 ppm SO2 in a stream containing 0.21 atm O2. The response time of the cell was 150 to 900 s at 873 K.
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  • Motoi Hara, Yoshiyuki Sato, Tokiko Nakagawa
    1996 Volume 60 Issue 10 Pages 962-969
    Published: 1996
    Released: April 04, 2008
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    The electrodeposition of tantalum on a nickel substrate was tried by using an equimolar NaCl-KCl molten salt containing 2.5 mol%K2TaF7 at 1073 K in air as an electrolyte. The electrodeposition was carried out by a cathodic potentiostatic polarization method. The mass of the electrodeposited material showed a maximum value in a potential region from −0.85 to −0.95 V (vs. Ag/Ag+(0.1)). The morphology and constituent of the electrodeposit were examined by SEM observation and EPMA and X-ray diffraction analysis. It was found that the deposit formed at −0.85 V consisted of a thin inner layer and a thick outer layer. The inner layer was dense and consisted mainly of the TaNi2 intermetallic compound, whereas the outer layer was not dense and consisted of δ-Ta2O5 and metallic tantalum crystals. The nickel specimen covered with the electrodeposit showed spontaneous passivation behavior in a similar manner as pure tantalum in a hot HNO3 solution. The high corrosion resistance of the specimen was probably attributable to the spontaneous passivation behavior of the thin inner layer consisting mainly of a Ta-Ni alloy.
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  • Zhang Gong, Atsushi Nishikata, Tooru Tsuru
    1996 Volume 60 Issue 10 Pages 970-979
    Published: 1996
    Released: April 04, 2008
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    Electrochemical impedance measurements of 31 alloys have been carried out in NaCl-KCl-Na2SO4-K2SO4-ZnSO4 melts under air containing H2O and HCl at 723, 773 and 873 K. Regarding relatively good corrosion resistant alloys, the interface of alloy/molten salt can be represented by an equivalent circuit model consisting of a charge transfer resistance, double layer capacitance solution resistance and finite diffusion impedance. Meanwhile, the impedance characteristics of poor corrosion resistant alloys can be explained by a transmission line equivalent circuit model in which the current distribution inside pores of thick porous oxide layers formed on the surface is considered. A good correlation was established between the reciprocal of impedance at 10 mHz and the corrosion rates calculated from mass loss after immersion tests. The AC impedance method was shown to be useful as rapid corrosion test for evaluating the corrosion performance of alloys in molten salt environments.
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  • Takeo Kubota, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto
    1996 Volume 60 Issue 10 Pages 980-987
    Published: 1996
    Released: April 04, 2008
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    ZrO2 thin films were formed by chemical vapor deposition using Zr(O-i-C3H7)4 and O2 at the substrate temperatures of 523-723 K. Changes in the thickness and refractive index of the films were measured by ellipsometry during deposition. The corrosion resistance of the films was tested in 1 kmol·m−3 HF. The decrease in film thickness of the test solution was determined by ellipsometry. The chemical composition of the films was analyzed by AES, XPS, and FTIR. The microstructure of the films was observed by TEM. It was found that the deposition rate and the corrosion resistance of the films became maximum when deposition was performed at 673 K and 623 K, respectively. There was a close relationship between the corrosion resistance and the refractive index of the films, that is, the highest corrosion resistance was attained on a film with the highest refractive index. The decreases in refractive index of films at the substrate temperatures lower and higher than 623 K were attributed to increases in the amount of OH bonds in the films and in the surface roughness of the films, respectively.
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  • Tetsuya Ishikawa, Mitsuharu Yamabe, Yoshinori Hara, Yasutoshi Noda
    1996 Volume 60 Issue 10 Pages 988-992
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The growth of ZnSe films was performed at 672∼723 K by metalorganic chemical vapor deposition using an atmospheric-pressure, rf-heated and horizontal reactor. Diethylzinc (DEZn) and diethylselenide (DESe) as source materials were fed by H2 gas with the [VI]/[II] ratio on a semi-insulation GaAs(100) substrate. Nitrogen trifluoride (NF3) was used as co-reactant. The growth rate estimated by the profile meter indicates that NF3 drastically enhanced the growth rate at the flux (fNF3) of about 0.3 μmol/s. The increased growth rate might be due to some chain reaction of dealkylation from DESe with NF3. Photoluminescence of the ZnSe films was measured at 77 K by using a He-Cd laser for excitation. For all the films grown at fNF3<0.3 μmol/s, the donor-acceptor(D-A) pair emission was observed in the spectra, which corresponds to that reported on the nitrogen-doped p-type ZnSe. The result indicates that the nitrogen atoms from NF3 might be incorporated into the grown films. At fNF3>0.3 μmol/s, the emission peak broadened in the region of 2.4-2.6 eV.
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  • Teruo Haibara, Kimihiro Ozaki, Keizo Kobayashi, Toshiyuki Nishio, Kenj ...
    1996 Volume 60 Issue 10 Pages 993-999
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The effect of additional ceramic powder on the formation tendency of an amorphous phase in a La55Al25Ni20 alloy was investigated by water quenching of molten alloy. The specimens were 12 mm in diameter and 6 mm thick. In the alloy without ceramic powder, the amorphous phase forms only near the surface of the specimen. By the addition of 6 vol% TiB2 powder, it was possible to produce a homogeneous alloy specimen with amorphous and crystalline phases. In order to analyze the role played by ceramic powder in this process, various kinds of ceramic powder were added. The TiC powder played the same role as the TiB2 powder in this process, but the TiN and ZrB2 powders did not. A crystalline phase about 20 μm thick was observed at the surface of TiB2 in the optical microstructure. By EPMA, this crystalline phase was confirmed to have a composition of poorer La and richer Al, Ni than the matrix phase. Since the crystal preferentially nucleate at the TiB2 surface and grows slowly, the matrix phase would be easily amorphized.
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  • Yuji Imashimizu, Jirô Watanabé
    1996 Volume 60 Issue 10 Pages 1000-1006
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Single crystals of Cu-0.01, 0.03, 0.05, 0.1 and 0.2 at%Au alloys were grown in the [111] direction under a given condition by the Czochralski method. The distribution and the density of edge dislocations formed in those crystals were examined by etching the (111) cross sections perpendicular to the growth axis. The results are discussed by referring to the dislocation formations in the copper and copper-aluminum dilute alloy crystals investigated in the previous work.
    (1) In the Cu-0.01 at%Au alloy crystals the slip dislocations revealed as arrays of etch pits along ⟨1\bar10⟩ directions are found on some cross sections, while most of the dislocations are randomly distributed. In the Cu-0.03 at%Au alloy crystals, no slip dislocations are observed and moreover the dislocation formation on the periphery of the crystals tends to be suppressed, resulting in the decrease in dislocation density to a minimum value which is about half that of copper crystals.
    (2) In the crystals containing gold more than 0.05 at%, a substructure of dislocation clusters and subboundaries tends to form and the dislocation density increases with increasing gold concentration. In the Cu-0.2 at%Au alloy crystals, the short subboundaries and dislocation clusters are distributed homogeneously, and the dislocation density becomes very high.
    (3) The dislocation density of the pulled crystals is reduced by a small addition of gold as well as aluminum, but the lowest density attained by gold addition is higher than that by aluminium addition. The reason is probably that copper-gold alloys give rise to constitutional supercooling during the melt-growth process more easily, so that the dislocation formation due to the segregation of solute atoms would occur at a low concentration compared with copper-aluminum alloys.
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  • Yo Tomota, Kazuyuki Kimura, Tetsuya Suzuki, Tokuzou Tsujimoto
    1996 Volume 60 Issue 10 Pages 1007-1012
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The changes in structure and properties of a hot-extruded mixture of Ti and Al-Mn alloy elemental powders during the reactive sintering were examined. The aim of this investigation was to change the maximum heating temperature of HIP treatment from the conventional 1653 K to lower temperatures.
    It was found that the density of 973 or 833 K HIP’ed material increased by subsequent heat treatment under atmospheric pressure. Especially, when the 973 K HIP’ed material was heat-treated at 1653 K, the density became comparable with that of 1653 K HIP’ed one. An interesting property was found in the 973 K HIP’ed material, i.e. it can easily deform under a low applied stress at 1273 K. This enables the microstructure of the 973 K HIP’ed material to be controlled widely by using thermomechanical treatment. Fully lamellar structure of 973 K HIP’ed material obtained by heating at 1653 K exhibits a texture. The texture is weakened by the 1273 K forging before heating.
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  • Setsuo Aso, Shoji Goto, Yoshinari Komatsu, Akira Muto
    1996 Volume 60 Issue 10 Pages 1013-1019
    Published: 1996
    Released: April 04, 2008
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    Chromium white-cast iron containing crystallized graphite (abbreviated as the A-alloy) may be considered as a composite-casting-material due to its structure consisting of three phases with different properties; M7C3 type eutectic carbide, austenite matrix, and graphite. Chromium white-cast iron containing crystallized graphite possesses both good wear resistance and strength similar to high chromium white-cast iron. Furthermore, it also possesses good lubricity due to the graphite; therefore, it is used as a material for finish rolls of stainless steel. The purpose of this study is to clarify the high-temperature compression-strength mechanism of the A-alloy compared with the B-alloy, an alloy without graphite but with a similar composition to that of the A-alloy. The form of the stress-strain curve shows the usual form with work hardening occurring at temperatures below 673 K; however, on the stress-strain curves at temperatures above 773 K, the maximum compression stress is reached at an early stage of deformation followed by a gradual decrease in the stress. The maximum compression strength of the A- and B-alloys at room temperature are approximately 2200 MPa and 2400 MPa respectively and decrease to about 1300 MPa at a temperature of about Tm/2 (700 K) on both alloys. The maximum compression strength of the A-alloy is slightly less than the B-alloy throughout all test temperatures. However, the strain rate dependence of maximum compression strength appears at temperature above 773 K on both the A-alloy and the B-alloy, that is, the strain rate sensitivity (m-value) can be obtained from the slope of linear relationship between ln σB and ln \dotε at each temperature; namely, m=0.03 at 773 K, m=0.08 at 873 K, and m=0.14 at 1023 K. Compressive failure is initiated by the deformation of graphite on the A-alloy, whereas on the B-alloy compressive failure is initiated by the crack of eutectic carbide caused by deformation of the large size matrix near the carbide. Therefore, it is presumed that in both alloys the compressive strength is maintained by the eutectic carbide, and their high-temperature deformation behavior is governed by the deformation of matrix.
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  • Takashi Hase, Kazuyuki Shibutani, Seiji Hayashi, Masao Shimada, Rikuo ...
    1996 Volume 60 Issue 10 Pages 1020-1028
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The bubbling density, i.e. the number of bubbles formed per unit length, in over 1 m long Ag-sheathed Bi2Sr2CaCu2O8+x (Bi-2212) superconducting tape was quantitatively investigated. The bubbling seemed to be associated with the sausaging phenomenon which was observed during deformation of the tape, which mostly occurred in two different temperature ranges of the heat treatment. The diffusion mechanism for gas formation inside of the tape in each temperature range is discussed. A newly developed heat treatment process which is performed in an evacuated atmosphere while controlling the heating rate completely prevented bubbling. It was also confirmed that a critical current density of 1.2×105 A/cm2 at 4.2 K in 0 T can be realized in a double pancake coil fabricated by the present improved process.
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  • 1996 Volume 60 Issue 10 Pages 1029
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Please see pdf. Wrong:Fig. 5 Right:Fig. 5
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