Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 66, Issue 7
Displaying 1-19 of 19 articles from this issue
  • Hidekazu Sueyoshi, Tomohito Maruno, Masahiro Asano, Yoshihiro Hirata, ...
    2002 Volume 66 Issue 7 Pages 677-683
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    Processing of a continuous ceramic fiber/iron alloy composite by powder metallurgy was investigated. The preparation of a continuous ceramic fiber-reinforced iron alloy is feasible by mixing of continuous ceramic fibers and iron alloy powders in an ultrasonic equipment with acetone, followed by hot isostatic pressing (HIPing) or hot pressing (HPing) at 1273 K. In HPing, a volume fraction of ceramic fiber in the composite in which ceramic fibers are distributed uniformly depends upon a diameter of ceramic fiber and a mean particle size of iron alloy powders. When a volume fraction of ceramic fiber is more than an optimum value, the excess fibers aggregate, resulting in nonuniform dispersion of ceramic fibers. On the other hand, nonuniform dispersion is also achieved because of the formation of ceramic fiber-free region when a volume fraction of ceramic fiber is less than the optimum value. In uniform dispersion of ceramic fibers, volume fraction of ceramic fibers in HIPed composite is higher than that in HPed composite. This is because ceramic fiber migration due to high stress occurs during HIPing. To obtain the composite with uniform dispersion of ceramic fibers, the specimen is to be uniformly deformed during HIPing.
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  • Michihisa Fukumoto, Motoi Hara, Yoshiyuki Sato, Toru Kidachi, Toshiro ...
    2002 Volume 66 Issue 7 Pages 684-689
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    A Ni aluminide layer on Ni substrate was formed by electrodepositing Al and alloying it with Ni in molten salt. Electrolysis of Al was conducted using potentiostatic polarization method at constant potentials in an equimolar NaCl-KCl melt containing 1∼5 mol%AlF3 at 1023 K. The mass of electrodeposited material increased with an increase in polarization potential. Deposits formed at −1.2∼−1.4 V(vs. Ag/Ag+(0.1)) built up a homogeneous layer. These deposits consisted of Ni aluminide such as Ni2Al3 and NiAl. Al content in deposit layers slightly decreased with increasing depth from the surface to the deposit/substrate interface. Nickel covered by the electrodeposit layer was more resistant than bare nickel to high temperature oxidation.
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  • Yukiko Oyama, Atsushi Nishikata, Tooru Tsuru
    2002 Volume 66 Issue 7 Pages 690-695
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    In the previous paper, the corrosion fatigue test of commercial pure iron had been performed in 5 mol/m3-chloride-containinig sodium borate and boric acid buffer solution of pH 8.39. The response current to the applied cyclical elastic deformation in two different strain waveforms, sinusoidal and trapezoidal was successfully simulated using two parameters, a decay factor and frequency of the applied strain waveform, where the decay factor is a parameter indicating the repassivation ability. The response current was found to be due mainly to charging or discharging current of electrical double layer before crack initiation and the current (damage current) due to iron dissolution and repassivation from the crack tips superimposed on the charging current after crack initiation. In this study, the effects of the decay factor and the frequency on the corrosion fatigue damage have been investigated.
    The simulation results showed that the amount of charge of the damage current increases with decreasing decay factor, and with increasing frequency under a constant period. The decrease in the decay factor implies the promotion of the anodic dissolution at the crack tip. In other words, the chemical process (corrosion) contributes largely to the crack propagation. On the other hand, since the increase in the frequency reduces the time factor for the progress of corrosion reaction in each strain cycle, the mechanical process becomes more important factor for the crack propagation in high frequency corrosion fatigue test.
    From the simulation results of the total current due both to the double layer charging or discharging and anodic dissolution (damage current), it was found that the increases in the ratio of the damage current increases the higher harmonic components in the response current and decreases the phase shift between the applied strain and the response current. Accordingly, the degree of corrosion fatigue damage can be detected by the monitoring of these harmonic components and phase shift.
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  • Keiichi Murase, Hideyuki Shigehara, Ryoichi Monzen
    2002 Volume 66 Issue 7 Pages 696-700
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    The effects of additions of Ag, Cr, Sb and P on the formation and growth of discontinuous precipitation (DP) reaction have been examined for different [001] symmetric tilt boundaries in a temperature range from 623 to 698 K using Cu-0.75 mass%Be alloy bicrystals. As the concentration of each element increases, the incubation period to initiate DP for a boundary increases, the cell growth rate for the boundary decreases, and both reach constant values. A detailed kinetic analysis of DP using the models by Turnbull and Petermann-Hornbogen has enabled to determine the grain-boundary diffusivity. At the stage in which the cell growth rate becomes a constant value, the activation energies Qb for boundary diffusion are in agreement with those Qv for bulk diffusion of the elements in Cu. For boundaries which have values of Qb lager than Qv before adding P, the boundary diffusivity is not affected by the P addition.
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  • Kenichi Nakajima, Hiromitsu Ino, Kohmei Halada
    2002 Volume 66 Issue 7 Pages 701-707
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    A methodology for the evaluation of material recycling in the life cycle inventory (LCI) was established. In this study the concept of “material” is introduced, by which the system is extended to the cases that the materials are transferred from outside to inside or vice versa of the boundary of the system. The extension of the system should be performed by means of the same way of the circulation one, in accordance with the principle of consistency of the function unit and the each system boundary. Based on this method the environmental loads of recycled materials such as secondary aluminum, casting aluminum and EAF steel were reasonably calculated and the effect of recycling was properly evaluated.
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  • Masaru Yokota, Fuminori Sugaya, Mifune Haruhisa, Yoshiyuki Kobori, Kat ...
    2002 Volume 66 Issue 7 Pages 708-714
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    We carried out the scientific investigations of the 16 ancient bronze mirrors produced mainly in the early and the late Hun Era in China, and the following results are obtained;
    (1) Among the 16 ancient bronze mirrors investigated here, pure copper deposition lumps were observed in or on the 15 mirrors except for one.
    (2) The rates of density reduction obtained from the measured and the calculated densities corresponded to the degree of corrosion of the mirrors.
    (3) The shapes of appearances of pure copper lumps in the mirrors show various modes, i.e., depositions like layers, large or fine particles, or depositions like string or flash of lightning just burring the cracks in the mirrors.
    (4) The environment of the pure copper depositions accompanies the metallographic irregularities occurred by the corrosion in the clay.
    (5) The oxide copper (Cu2O) layers and particles were observed in the mirrors showing just the same shapes as those of pure copper depositions.
    (6) Non-corroded matrices of the all bronze mirrors investigated here contain about 2 mass% of Pb, 18 to 26 mass% of Sn and the residue of Cu.
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  • Toshikazu Akahori, Mitsuo Niinomi, Tomoya Maekawa, Hisao Fukui, Akihir ...
    2002 Volume 66 Issue 7 Pages 715-722
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    CP titanium and titanium alloys have been used as biomaterials. Recently, β type titanium alloy, which has good biocompatibility, low modulus, excellent balance of strength and ductility, is widely expected to use for biomedical applications. Very recently, Ti-29Nb-13Ta-4.6Zr alloy is newly designed and developed for biomedical applications. The new alloy is composed of non-toxic elements such as Nb, Ta, and Zr. In present study, various phases appeared in the new alloy according to the various aging treatments were characterized by hardness tests and microstructural observations. Tensile and fatigue properties of the new alloy were also investigated with relating microstructure. Precipitated phases distributed homogeneously over the whole specimen are α and ω phases, when the new alloy is aged at 673 K for 259.2 ks after solution treatment at 1063 K for 3.6 ks. The best balance of strength and elongation in the new alloy was obtained by the condition of 673 K for 259.2 ks after solution treatment at 1063 K for 3.6 ks. Fatigue limit of the new alloy aged at 673 K for 259.2 ks is around 700 MPa.
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  • Shuetsu Haseyama, Shuji Yoshizawa, Norifumi Murakami
    2002 Volume 66 Issue 7 Pages 723-727
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    Thick Bi2Sr2CaCu2Ox(Bi-2212) films prepared by partial melting is widely used with cables, magnetic shields, etc. as their critical current density (Jc) is very high. The samples were prepared by spraying Bi-2212 paste on Ag substrata, and then by partially melting these to the thickness of 50 μm. During production, optimum atmospheric pressure, heat treatment, cooling speed and annealing time had to be applied to obtain high Jc values and critical temperature. As the best condition for heating the samples in optimum oxygen concentration, the samples were melted for 600 s at 1163 K in oxygen, and then cooled by the rate of 0.2 K/min. The highest Jc so far was obtained with these samples and Tc also increased to 91 K. When the sample was heat treated for 54 ks at 773 K in nitrogen, Jc improved to 120 A/mm2 at 77 K and 0 T.
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  • Kazuma Tsuzuki, Naoki Ide, Shigeru Asano
    2002 Volume 66 Issue 7 Pages 728-734
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    The elementary process of solid solution hardening is the dislocation motion overcoming solute atoms in a crystal. The motion of an extended dislocation in Cu-Au solid solution alloy has been investigated by molecular dynamics simulation using Morse-type potential. Firstly, the equilibrium core structure of an extended dislocation is constructed in a pure Cu crystal. The spacing of partial dislocations is 5.2 nm for the edge dislocation and 1.8 nm for the screw dislocation. These results are consistent with experimental observations. The Peierls stress is 12×10−4 G for the edge dislocation and 20×10−4 G for the screw dislocation, where G is the shear modulus. Substitutional solute Au atoms are inserted into the region adjacent to the slip plane in front of the extended dislocation, and shear stress is applied to the crystal. The stress required to make the dislocation pass over Au atoms is 123−146×10−4 G for the edge dislocation and 112−126×10−4 G for the screw dislocation. The stress to move the screw dislocation is comparable to that to move the edge dislocation on condition of the same solute content. Thus, not only the edge dislocations but also the screw dislocations contribute to the initial stage of slip deformation in Cu-Au solid solution alloys.
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  • Byung Il Kim, Hyeoung Ho Park, In Sung Bae, Jae Sik Yoon
    2002 Volume 66 Issue 7 Pages 735-739
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    Pure tantalum powder has been produced by combining Na as a reducing agent, K2TaF7 as feed material, KCl and KF as a diluent in a stainless steel (SUS) bomb, using the method of metallothermic reduction. The present study investigated the effect of the temperature and the amount of the reductant on the characteristics of tantalum powder in the production process and on the yield. The temperature applied in this study ranged from 800 to 980°C, and the amount of the additional reductant varied from −10%, 0%, 5%, and 10% of the theoretical amount used for the reduction of the entire K2Ta F7. The results showed that as the temperature and the additional reductant increased, the yield of the powder increased from 57 to 94%, and the particle size also increased from 0.4 to 5.0 μm. On the other hand, the amount of minute tantalum powder decreased significantly, from 93 to 60%, with the increase of temperature and the amount of the reductant. At the reduction temperature of 920°C and with the 5% excess of the reductant, the average size of the particle, 2-4 μm, was closest to that of the particle commonly used, 2-5 μm. Also, under this condition, impurities contained in the powder were within the limit allowed for the commonly used product.
    The present study concluded that the optimal condition for manufacturing tantalum powder of the best quality was the reduction temperature of 920°C and the reductant of 5% excess.
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  • Yasuhiro Kawaguchi, Noriko Nakamura, Satoru Yusa
    2002 Volume 66 Issue 7 Pages 740-744
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    Since positron annihilation lineshape analysis can evaluate the degree of fatigue damage, detecting defects such as dislocations in metals, we used the method to evaluate the degree of fatigue damage in a type 316 stainless steel pipe, which is used in the primary system of a nuclear power plant. Using 68Ge as a positron source, an energy spread of annihilation gamma ray peak from the material was measured and expressed as the S-parameter.
    Actual plant material cut from a surge line pipe of a pressurizer in a pressurized water type nuclear power plant was measured by positron annihilation lineshape analysis and the S-parameter was found. Comparing the S-parameter with a relationship between the S-parameter and fatigue life ratio of the type 316 stainless steel, we evaluated the degree of fatigue damage of the actual material. Furthermore, to verify the evaluation, microstructures of the actual material were investigated by TEM (transmission electron microscope) to observe dislocation densities. As a result, a change in the S-parameter of the actual material from standard as-received material (type 316 stainless steel) was in the range from −0.0013 to 0.0014, while variations in the S-parameter of the standard as-received material were about ±0.002; differences between the actual material and the as-received material were not significant. Moreover, the dislocation density of the actual plant material observed by TEM was almost the same as that of the as-received material. In conclusion, we could verify the evaluation of the positron annihilation lineshape analysis for fatigue damage.
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  • Masao Hayakawa, Satoshi Terasaki, Toru Hara, Kaneaki Tsuzaki, Saburo M ...
    2002 Volume 66 Issue 7 Pages 745-753
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    Quantitative microstructure analyses by atomic force microscopy (AFM) were performed for two kinds of JIS-SCM440 steel with the tensile strength of 1580 MPa; the modified-ausformed and tempered (MAQT) martensite and the conventional quench-tempered (CQT) martensite, where the critical diffusible hydrogen content for delayed fracture in the MAQT martensite was 0.53 mass ppm and higher than that of the CQT martensite (0.13 mass ppm). Size distribution of cementite particles and martensite blocks was measured to understand the relationship between microstructure and hydrogen embrittlement resistance. The average cementite size along prior austenite grain boundaries for the MAQT martensite was 0.51 times of that for the CQT martensite. Coarse film-like cementites above 200 nm in length markedly decreased for the MAQT martensite. As the result, occupied fraction of grain boundary cementite particles for the MAQT martensite was decreased to 41% from 51% of the CQT martensite. Inner-prior austenite grain cementite and block were refined for the MAQT martensite. The average cementite size of inner-prior austenite grains for the MAQT martensite was 0.58 times of that for the CQT martensite. The average block width was 0.38 μm for the MAQT martensite, while it was 0.49 μm for the CQT martensite. It is suggested that the refinement of the MAQT martensite structure along and inner-prior austenite grain boundary plays an important role in improvement of hydrogen embrittlement resistance.
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  • Shuichi Mitoma, Ichimitsu Itabashi, Shin Takaura, Hiroto Osono
    2002 Volume 66 Issue 7 Pages 754-759
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    This study investigates the influence of trace added calcium or palladium on the annealing characteristics of cold-worked pure gold. The electrical resistance of Au-0.018 mol%Pd, Au-0.020 mol%Ca, and pure gold (99.999 mass%) were measured in the temperature range from room temperature to 873 K. The samples were annealed at temperatures where peculiar changes in electrical resistivity were observed and subsequently investigated through tensile tests, metallographic observations, and transmission electron microscopy.
    The electrical resistivity of Au-0.018 mol%Pd and pure gold decreased rapidly between 340 K and 390 K. Within this temperature range, mechanical properties of the sample also changed rapidly toward recrystallization. The electrical resistivity of Au-0.020 mol%Ca was observed to decrease in 3 gradual steps between 410 K and 750 K. The mechanical properties also changed gradually over this temperature range. Recrystallization structures were observed at 750 K.
    Whereas the recovery and recrystallization of cold-worked pure gold was unaffected by the addition of trace palladium, these processes were significantly affected by trace added calcium. This appears to be related to the fixing of dislocation with calcium atoms and the strong interaction between vacancies and calcium atoms.
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  • Sutandyo Andiarwanto, Hiromi Miura, Taku Sakai
    2002 Volume 66 Issue 7 Pages 760-766
    Published: 2002
    Released on J-STAGE: April 24, 2008
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    Preferential occurrence of dynamic recrystallization (DRX) at triple junction (TJ) in pure copper tricrystals was investigated. DRX at TJ preferentially occurred at lower strain than the peak strain (about 2/3). All of the nucleated DRX grains at TJ were twins. Grain-boundary sliding (GBS) was supposed to cause high stress concentration and deformation concentration near TJ because GBS was impeded at TJ. The twins were seemed to be nucleated behind the grain boundary migrating along the folding which was formed by impediment of GBS at TJ. These combined effects were supposed to cause the preferential DRX nucleation at TJ during high temperature deformation.
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  • Hitoshi Matsuura, Yoichi Nishino, Uichiro Mizutani, Shigeru Asano
    2002 Volume 66 Issue 7 Pages 767-771
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    We report on the temperature dependence of electrical resistivity, Seebeck coefficient and Hall coefficient for Fe2(V1−yTiy)Al with y=0−0.25 and Fe2(V1−zMoz)Al with z=0−0.20. While the Heusler-type Fe2VAl (y=z=0) exhibits a semiconductor-like resistivity behavior, a slight substitution of Ti or Mo for V causes a sharp decrease in the low-temperature resistivity and a large enhancement in the Seebeck coefficient S: a sign of S is positive for the Ti substitution but negative for the Mo substitution. Substantial enhancements for the Seebeck coefficient are in reasonable accord with changes in the Hall coefficient and can be explained on the basis of the electronic structure of Fe2VAl, where the Fermi level is expected to shift slightly from the center of the pseudogap upon the substitution of Ti or Mo for V. In particular, the Mo substitution leads to a large power factor of 4×10−3 W/mK2 at room temperature, which is comparable to that of conventional thermoelectric materials.
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  • Hisao Tanaka, Won-Yong Kim, Akio Kasama, Ryohei Tanaka, Yoshinao Mishi ...
    2002 Volume 66 Issue 7 Pages 772-777
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    Room temperature compressive strength and fracture toughness of two-phase Nbss/Nb5Si3 intermetallics alloyed with Mo are investigated in terms of chemical compositions, and microstructures that were modified by various processing techniques; arc melting, isothermal forging, non-crucible directional solidification(DS). Three types of microstructures are characterized by processing; maze-like structure for arc melting, equiaxed structure for isothermal forging and lamellar structure aligned to growth direction for DS. The Nb5Si3, coexisting with Nbss in Nb-xSi-15Mo alloys, is found to change the crystal structure from α to β accompanied by the increasing Mo content and heat treatment temperature. The yield strength of the two-phase alloy consisting of α-Nb5Si3 and Nbss is higher than that obtained in the alloy consisting of β-Nb5Si3 and Nbss, irrespective of the same chemical composition and volume fraction for both the alloys. The fracture toughness of the arc-melted alloys with a maze-like structure is found to be higher than that of the DS alloys with a fine aligned microstructure. On the basis of experimental results, it is suggested that the fracture toughness of the two-phase Nbss/Nb5Si3 alloys depends primarily on morphology, thickness and solid solution hardenability of the incorporated Nbss but does weakly on volume fraction of constituent phases and phase transformation.
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  • Shozo Inoue, Kenji Nagai, Masahito Niibe, Keiji Koterazawa, Mikio Iwas ...
    2002 Volume 66 Issue 7 Pages 778-783
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    We have deposited Ti/C multilayer films onto glass and Si wafer substrates by dc magnetron sputtering. The structure and the mechanical properties of multilayer films with various periods have been investigated. The multilayer films, of which periods were longer than 1.16 nm, showed diffraction peaks in low angle XRD patterns corresponding to their artificial layered structure. The Ti layer in the multilayer film was found to be amorphous when the period was less than about 5 nm. The roughness of Ti/C interface appeared to be larger than that of W/C multilayer system, which should be caused by a tendency of Ti layer to grow with a columnar structure. The hardness of Ti/C multilayer films was found to be constant when the period was larger than 2 nm. As the period decreased less than 2 nm, the hardness increased rapidly and reached nearly to the hardness of TiC single layer films. This should be caused by the increase in relative quantity of Ti-C bonds in the films.
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  • Yasuhiro Hoshiyama, Hidekazu Miyake, Kenji Murakami, Hideo Nakajima
    2002 Volume 66 Issue 7 Pages 784-791
    Published: 2002
    Released on J-STAGE: April 24, 2008
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    A composite powder is produced by ball-milling of elemental titanium, aluminum and aluminum nitride powders in an argon atmosphere, and is plasma-sprayed in an argon atmosphere, yielding titanium aluminide-based deposits. The constituents of the as-sprayed deposit are Ti3Al (α2), TiAl (γ) and Ti2N. Heat treatment of the as-sprayed deposit results in the formation of Ti2Al(C, N). The carbon in Ti2Al(C, N) is incorporated into the composite powder during ball-milling due to decomposition of methanol which is used as process controlling agent. There is little difference in hardness between the as-sprayed deposit and the deposits heat-treated at temperatures up to 1473 K. Hardness of the as-sprayed deposit and the heat-treated deposits are higher than that of the cast titanium-aluminum binary alloy whose titanium and aluminum contents are similar to those of the sprayed deposit.
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  • Tomoyuki Nishida, Hidekazu Sueyoshi
    2002 Volume 66 Issue 7 Pages 792-798
    Published: 2002
    Released on J-STAGE: April 24, 2008
    JOURNAL FREE ACCESS
    C/C composites were bonded to nickel in vacuum, using an RF-induction furnace, with joining temperature, keeping time and joining compressive stress as variables. C/C composites with different carbon fiber orientations and heat treatment temperatures were used. The bending strength of the C/C composite/nickel joints was investigated. The fracture surface of the joints was observed using a scanning electron microscope. X-ray diffraction was performed on the joining surface of C/C composites. Changes in the microstructure and hardness of nickel near the joining interface were investigated. On the basis of the results of these experiments, the influences of carbon fiber orientation and graphitization on the solid-state bonding of C/C composite to nickel were examined.
    A large difference in thermal expansion coefficients between the longitudinal section of carbon fiber and nickel results in delamination at the interface. In the bending test, when the longitudinal section of carbon fiber is parallel to the joining surface, slip due to crystallographic anisotropy occurs. Therefore, good bonding between the longitudinal section of the carbon fiber and nickel is not achieved. On the other hand, good bonding to nickel along the cross section perpendicular to the carbon fiber axis becomes feasible. Therefore, in plain woven carbon fiber-reinforced carbon composite/nickel joints, the bending strength is low, while in unidirectional carbon fiber-reinforced carbon composite/nickel joints, the bending strength is equivalent to that of C/C composite.
    The degree of graphitization affects the joining quality. Strong bonding of C/C composite to nickel is accomplished with the progress of graphitization. The bending strength of the joint is equivalent to that of C/C composite.
    The bending strength of C/C composite/Ni joints is affected by the joining temperature, keeping time and joining compressive stress, because these factors are related to full contact of joining surfaces and diffusion of carbon atoms from C/C composite into nickel.
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