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Volume 39, Issue 10
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[in Japanese]1992 Volume 39 Issue 10 Pages 814
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (82K) -
Hiroaki Kohmoto, Noriaki Murahashi, Tohru Kohno1992 Volume 39 Issue 10 Pages 815-818
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSRapidly solidified niobium aluminides (Nb3Al) have been studied to understand their ability as structural materials for ultra-high temperature applications. A new gas atomization process combined with plasma-skull-melting without any refractory, refractory metal and ceramic, has been developed to produce ultra-clean powders. In this process, named Plasma-Melt-Gas-Atomization (PMGA), a pouring nozzle for molten metal stream is made of water-cooled copper with a bottom hole. Rapidly solidified powders of Nb3Al have been successfully obtained. Mean diameter of the powders is around 100μm, and oxygen content is 300ppm. PMGA'ed powders of Nb-22at%Al mostly consists of supersaturated solid solution of Al in Nb (bcc), although cast ingot of same composition wholly consists of ordered A15. Because microstructure of powder is identical to melt-spun ribbon, solidification rate of PMGA can be considered very high.View full abstractDownload PDF (1321K) -
Atsushi Kakitsuji, Hiroki Miyamoto1992 Volume 39 Issue 10 Pages 819-822
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMoSi2-Al203 composites with 0-50 vol% Al203 were in-situ fabricate by self-propagating high temperature synthetic process. The compacts of the powder mixture of MoO3, Al, Si and MoSi2 were encapsulated in Pyrex tube and then HIP'ed at 1573K under pressure of 196MPa. Self-propagation synthesis reaction occurred during elevated temperature and pressure.
Relative density of HIP'ed samples decreased with increasing addition of MoSi2 pre-alloyed powder to the starting powder mixture.
Vickers hardness and fracture toughness were performed to investigate the mechanical property of composites. Vickers hardness increased linearly with increasing volume fraction of Al2O3 tested. The indentation fracture toughness of 50 vol% Al2O3 composite was two times lager than that of monolithic MoSi2.View full abstractDownload PDF (2507K) -
Koichiro Koyama, Masao Morishita, Kenji Suzuki, Satoru Yagi1992 Volume 39 Issue 10 Pages 823-829
Published: October 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSA New ternary Al-Ti-N alloy was prepared by the reaction sintering of pure aluminum powder and TiN powder. The results are as follows :
(1) The alloy become hard on reaction sintering. This hardening is caused by the formation of an intermetallic compound, A13Ti and a nitride, A1N during sintering.
(2) The AIN phase is formed at the sites where the TiN particles existed before reaction sintering while the Al3Ti phase appears to form a concentric circle like structure around these A1N particles. Therefore, this alloy is a composite material.
(3) The high-temperature hardness of this alloy is very much higher than that of a conventional Al-based high-strength alloy, 7075-T6. This alloy is expected to be a hopeful material.View full abstractDownload PDF (5380K) -
Masatomo Kamada, Setsuo Takaki, Youichi Tokunaga1992 Volume 39 Issue 10 Pages 830-835
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSComposite powder of intermetallic compound (TiAl) and carbide (TiC) was prepared from elemental powders of titanium, aluminum and graphite by means of mechanical alloying, and the formation process of the composite was investigated in relation to the solid state reactions among the elemental powders.
Mixed powders with a chemical composition of Ti-25at%Al-25at%C were mechanically milled in vacuum with centrifugel boll mill. After 10.8ks milling, lamellar structure of titanium and aluminum was formed, and graphite seemed to be finely crushed and included into the powder. The solid state reactions forming the composite microstructure occured after about 12ks milling. At first, finely dispersed graphite reacts with titanium to form TiC, and then local temperature rising caused by the exothermic reaction, Ti + Al → TiC + 180 kJ/mol, activates the diffusion between titanium and aluminum, which enables the elements to form the intermetallic compound (TiAl). The microstructure of TiC/TiAl composite powder prepared by this process is so fine that the components can not be distinguished with EPMA, although they can be identified by means of X-ray diffraction technics.View full abstractDownload PDF (4732K) -
M.Sherif El-Eskandarany, Kenji Sumiyama, Kiyoshi Aoki, Kenji Suzuki1992 Volume 39 Issue 10 Pages 836-841
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAmorphous Al-50at.% TM (TM; Ti, Zr and Ta) alloy powders have been synthesized by mechanical alloying (MA) and mechanical disordering (MD) using the rod-milling technique. The results show that the MA process for producing amorphous alloys is classified into three stages, while the crystal-to-amorphous transformation via the MD process occurs through one stage. At the intermediate stage of the MA time, the crystalline rod-milled Al-50at.% TM alloys have been transformed completely into amorphous phase at about 700 K by thermally assisted solid state amorphization reaction (TASSA). Contrary to this, the amorphous formation at the final stage of the MA occurs only due to the mechanically driven solid state amorphization (MDSSA).View full abstractDownload PDF (4883K) -
Tsuyoshi Itsukaichi, Takayuki Norimatsu, Minoru Umemoto, Isao Okane1992 Volume 39 Issue 10 Pages 842-846
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe structural development with milling time during mechanical alloying (MA) of Al, Ni and Ti powders in the compositions of Al65Ni10Ti25 and Al25Ni50Ti25 was investigated by x-ray diffraction and DSC. The MA powders were sintered by hot press. The phase, microstructure and hardness of the sintered compacts were studied using x-ray diffraction, SEM and vickers hardness tester. An amorphous phase was formed on final alloying stage for both the compositions. The ternary intermetallics of Al6.5NiTi2.5(π) and AlNi2Ti(σ) were confirmed to form on heating the well-milled powders. The optimum MA times for sintering to obtain the chemical homogeniety and enough hardness were found to be longer than 1800ks for Al65Ni10Ti25 and longer than 360ks for Al25Ni50Ti25.View full abstractDownload PDF (2215K) -
Tsuyoshi Itsukaichi, Shuji Ohura, Minoru Umemoto, Isao Okane1992 Volume 39 Issue 10 Pages 847-850
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSElemental Powders of Ni and Ti with the composition of Ni33Ti67 were mechanically alloyed for various periods of time by a holizontal ball mill. Changes of shape and phase of the processed powders with processing time were studied using SEM, x-ray diffraction and DSC. The MA powders were sintered by hot press. The phase, microstructure, relative density and hardness of sintered compacts were studied using SEM, TEN, x-ray diffraction and vickers hardness tester. The existence of an amorphous phase was confirmed as final alloying stage, which was identified by x-ray diffraction and DSC. A single NiTi2 phase was formed on sintering of well-milled powders. The optimum MA time for sintering with respect to the chemical homogeniety, relative density, and hardness of the sintered compacts was found to be longer than 360ks.View full abstractDownload PDF (3275K) -
Tsuyoshi Itsukaichi, Shuji Ohura, Minoru Umemoto, Isao Okane1992 Volume 39 Issue 10 Pages 851-854
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe structural development with milling time during mechanical alloying (MA) of Ni and Ti powders with the composition of Ni75Ti25 was investigated by SEM, x-ray diffraction and DSC. The MA powders were sintered by hot press. The phase, microstructure and hardness of the sintered compacts were studied using x-ray diffraction, SEM, TEM, and vickers hardness tester. Ni solid solution with an amorphous phase was formed in the final alloying stage, which was identified by x-ray diffraction and DSC measurements. The appropriate MA time to obtain a well-sintered compact with respect to the chemical homogeniety, relative density and hardness was found to be longer than 360ks.View full abstractDownload PDF (4512K) -
Kazuhiko Majima, Yuji Kaneko, Norihiro Takanashi, Shigeru Katsuyama, H ...1992 Volume 39 Issue 10 Pages 855-859
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffects of Co addition on sintering behavior of NdFeB ternary alloy powder were investigated through observation of microstructure and measurements of DTA and linear shrinkage. In the case of NdFeB powder, shrinkage started at 940K corresponding to the appearance of a liquid phase, which was derived from ternary eutectic reaction between Nd-rich, Nd2Fe14B and Nd1.1Fe4B4 phase. Although the shrinkage below 1273K was very small because of a lack in the amount of the liquid phase, remarkable shrinking occured when sintering temperature was raised above 1273K. This is probably due to increase of the amount of the liquid phase formed by the eutectic and peritectic reactions between Nd-rich, Nd2Fe14B and Nd1.1Fe4B4 phase. In the case of Co addition the starting point of shrinkage as well as that of remarkable shrinking shifted to a lower temperature than the NdFeB ternary specimen. This can be explained by the formation of the liquid phase derived from Nd-Co compounds.View full abstractDownload PDF (2398K) -
Tsuyoshi Itsukaichi, Munetaka Hosokawa, Minoru Umemoto, Isao Okane, Sa ...1992 Volume 39 Issue 10 Pages 860-864
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMechanical alloying was applied to prepare the permanent magnets of ThMn12-type NdTMcFe12-c nitrides for TM=Cr, Mo, Ti, V. Cr-Mo and Mo-Ti. After isothermal aging and nitrogenation, NdTMcFe12-c nitrides were obtained in the alloys of TM=15(at%)Cr, 15Mo, 7.5Cr-7.5Mo, 4Mo-4Ti, 7.5Mo-7.5Ti. Relatively high coercivities of 500 and 45OkA/m were obtained in NdMo2Fe10Nx and NdCrMoFe10Nx compounds, respectively. Crystal size smaller than 100nm was observed in NdMo2Fe10Nx powder by TEM and x-ray diffraction. This ultra fine crystal size was considered to be the origin of observed high coercivity.View full abstractDownload PDF (1298K) -
Takeo Tanaka, Saburo Nasu, Keiichi N. Ishihara, Paul Hideo Shingu1992 Volume 39 Issue 10 Pages 865-869
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMechanical alloying (MA) for Fe-C-Si mixtures of elemental powders was performed by a conventional ball-mill under an argon gas atmosphere. The phase formation on the ball-milling process was studied by X-ray diffractometry and differential scanning calorimetry.
An addition of silicon suppressed the formation of iron-carbides to promote the amorphization. For high silicon concentration, intermetallic compounds such as FeSi, β-FeSi2 and SiC were formed after indicating the partial amorphous formation. The inhomogeneous reaction, the slow reaction, which is a characteristic in MA of metal-nonmetal systems, was confirmed for Fe-C-Si system.View full abstractDownload PDF (295K) -
Shigeru Ito, Jiro Hirose, Nobuyuki Koura1992 Volume 39 Issue 10 Pages 870-874
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFeSi2 thermoelectric generator was prepared by Hot Isostatic Pressing (HIP). Mixture of Fe and Si powders was melted at 1350°C to form metallic phases of α-Fe2Si5 and ε-FeSi. After powdering process, Hipping was performed at 840-960°C for 30min under 10-100MPa. In the temperature range of 840-960°C, the metallic phases of α-Fe2Si5 and ε-FeSi were simultaneously transformed into the β-FeSi2. The suitable conditions for the densification and the transformation was decided as follows, temperature: 900°C, pressure: 5OMPa, time: 30min. The thermoelectric generator with PN junction was prepared under these conditions, doping 3at% of Mn for P-type and lat% of Co for N-type. At a temperature difference of 640°C between the junctions, the open circuit voltage was 300mV and the maximum power output was 13mW.View full abstractDownload PDF (1458K) -
Kiyotaka Kato, Yoshihiko Nozaki, Akihiro Matsumoto1992 Volume 39 Issue 10 Pages 875-878
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMatal injection molding (MIM) was applied to TiAl alloyed powder. The properties of sintered TiAl fabricated by this process were investigated. Fine TiAl powder(average grain size:10 μm) was mixed with the binder consisted of wax and acryic resin at the content of 42vo1%. This compound was injected to the shape of tensile test piece. This green compacts were debinded in various atomosphere (Air, Ar and N2), then sintered in vacuum (10-5Torr). Bulk density of sintered test piece was 3.6-3.7g/cm3, when it was sintered at 1400°C. Tensile strength at R.T. was about 35kgf/cm2. Fine alumina(Al2O3) was observed in the sintered test piece.View full abstractDownload PDF (1565K) -
Toshimasa Morooka, Eiji Yuasa, Matsuru Kushida1992 Volume 39 Issue 10 Pages 879-883
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAmorphous alloy powder of Cu-57at%Ti was prepared by the mechanical alloying of the elemental titanium and copper powder by using a Spex Mixer/Mill model 8000. The influence of pressure on crystallization temperature was investigated by X-ray diffraction and differential thermo analysis. No influence of pressure for making the compacts was observed. But, the crys-tallization temperature increased with the applying pressure during sintering. This increase rate was about 38K/GPa.View full abstractDownload PDF (250K) -
Yong Ho Park, Hitoshi Hashimoto, Ryuzo Watanabe1992 Volume 39 Issue 10 Pages 884-890
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTi and Al powder mixtures with nine compositions(Ti-10at.%Al-90at.%Al) were milled with milling balls of various sizes(2.0-19.1mm) by a vibratory ball mill and were sintered by HIP (Hot Isostatic Pressing). The microstructure and material properties of the sintered compacts were investigated by optical microscopy, SEM. TEM, X-ray diffraction, microhardness measurement, electrical resistivity mesaurement and modified small punch(MSP) test. It was found that the microstructure and the material properties of the sintered compacts were strongly dependent on the milling ball size, milling time and the starting powder composition. A nearly single phase intermetallic compound with more refined structure and higher MSP energy and strength was formed on longer milling time. The sintered compact with the starting composition of Ti-50at.%Al showed the highest MSP strength and energy, which can be related to the well refined microstructure with ultrafine dispersoids of Ti.Al in TiAl matrix.View full abstractDownload PDF (4062K) -
Shouichi Ochiai, Yo Kojima1992 Volume 39 Issue 10 Pages 891-896
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAs representative Ni aluminides, NiaA1 (26, 27at%Al), NiiAl+NiAl (32, 38at%Al) and NiAl (42, 46at%Al) intermetallic compounds were produced by mechanical alloying (MA) process for the purpose of refining microstructures. MA was performed in the attritor mill using pure nickel and NiAl prealloyed powders. MA treated powders were consolidated using the vacuum hot pressing. Produced aluminides showed fine grain microstructures with average grain size under 4 pm and had relative density above 97%. Each of them, however, contained a few percent of alumina which was made by oxidation of Al during MA treatment. This causes the decrease of Al content of at most 2 at%A1 compared with blend composition. High strengths over 1000 MPa and large fracture strain of more than 15% at room temperature were found for all of the alloys. Furthermore, it was confirmed that the flow stress of two phase alloy was larger than that of mono-phase alloys in the temperature range from room temperature to 1073K. The high strain rate sensitivity exponent (m value) of more than 0.3 was obtained for Ni3Al at 1073K and this is considered to be associated with the development of superplastic deformation.View full abstractDownload PDF (1691K) -
Nobushige Hiraishi, Kazutaka Asabe, Mutuo Nakanishi1992 Volume 39 Issue 10 Pages 897-900
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIt is well known that Ni3Si intermetallic compounds have an excellent corrosion resistance in a H2S04 solution. However, these compounds are hard to be worked when prepared by the conventional ingot metallurgy process because of their poor ductility and the ease of segregatation. Therefore, mechanical alloying (MA) has been tried to prepare intermetallic compounds with improved workability. In this paper, we investigated a process based on the MA method that yields fine Ni-Si mixtures with improved workability. By controlling the initial compositions of the mixtures and the MA conditions, it is possible to obtain required ratios among α, β and γ phases in sintered-compacts. As a result of the developed process, the workability of the obtained sintered-compacts at high temperatures has been remarkably improved. This process could be applicable to other intermetallic-compound systems.View full abstractDownload PDF (2668K) -
Toshio Shimoo, Hideya Inagaki, Kiyohito Okamura, Kuniaki Honjo1992 Volume 39 Issue 10 Pages 903-907
Published: October 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe oxidation mechanism of Nicalon coated with CVD⋅SiC layer was studied. Using CH3SiCl3-H2 gas mixture, CVD⋅SiC was deposited on Nicalon fiber heated at 1473K. The rate of oxidation was measured with a thermobalance in O2 stream at temperatures from 1473 to 1773K. The reaction products were examined by X-ray diffraction and SEM observation.
The oxidation film was formed at the skin. of CVD⋅SiC layer. Neither oxidation nor pyrolysis proceeded in Nicalon coated with CVD⋅SiC. The oxidation rate of CVD⋅SiC was slower than that of Nicalon. The oxidation rate of CVD⋅SiC followed the parabolic rate law. The activation energy was 186kJ/mol. It is considered that the oxidation rate is controlled by the gaseous diffusion through the micro-pores in the oxide film.View full abstractDownload PDF (2148K) -
Fumio Matsumoto, Syuichiro Kato, Yoichi Tomii1992 Volume 39 Issue 10 Pages 908-912
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDiamond films were prepared on SiC substrates with four kinds of CH4-H2 reactant gases (3, 5, 7 and 10% CH4 concentration) using plasma jet CVD. The growth rate of films was a maximum of 3μm/min at 5% CH4 and was approximated to 2μm/min at other CH4 concentrations. Properties of the deposited films were investigated by SEY, TEX, micro Vickers hardness test, XRD analysis and Raman spectra analysis. The films deposited at lower CHI concentration had an agglomerate structure of idiomorphic grains and the morphology of diamond films changed to a predominating {100}face from a {111}face with an increase of CH4 concentration from 3% to 5%. The films deposited at high CH4 concentration were composed of fine diamond crystals and non-diamond materials. The best Raman spectrum indicating the diamond films of crystalline perfection and of the lowest density of non-diamond materials was obtained at 5% CH4 with the maximum growth of {100} face.View full abstractDownload PDF (4153K) -
Toshio Shimoo, Ken-ichi Kakimoto, Kiyohito Okamura1992 Volume 39 Issue 10 Pages 913-917
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSUsing two types of Tyranno fibers T-1(18X0) and T-2(13%0), the mechanism of oxidation was investigated. The oxidation rate was determined by thermogravimetric analysis.
The initial rate followed the equation for reaction control. The rate constant kp of T-1 was nearly equal to that of T-2. The activation energy was 188kJ/mol. In the late stage, the oxidation rate was described by the equation for diffusion control. The rate constant kp of T-1 was larger than that of T-2, The temperature dependence of kp was complicated. When the continuous layer of silica was formed around Tyranno, the rate-determining step changed from the interfacial reaction to the gaseous diffusion through the micro-pores in the oxide film.View full abstractDownload PDF (285K) -
Eiichi Sentoku, Hironobu Kashimoto, Yoshio Fujimura1992 Volume 39 Issue 10 Pages 918-921
Published: October 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSGlass-ceramics consisting of fluor-phlogopite can be machined with tight tolerance, using conventional metal working equipments and tools. The purpose of this paper is to estimate machinability of glass-ceramics on turning. The estimation of machinability was carried out from the viewpoint of fracture mechanism of glass-ceramics. This fracture mechanism was observed by SEM device, and the breaking load by the indentation device was measured. The results obtained are as follows: (1) A device for the indentation test of material was made and a fracture energy of glass-ceramics concerning the extension of micro crack was estimated. (2) The extension mechanism of crack in the ceramics changes as the loading rate of indentation increases. (3) The energy of fracture and cutting has a high correlation. (4) The wear rate of tool can be forecasted from fracture energy.View full abstractDownload PDF (2538K) -
Noriko Tsuchiya, Hisao Kimura, Sil Mook Lim, Yasushi Nakamura1992 Volume 39 Issue 10 Pages 922-928
Published: October 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSEquilibrium experiments were performed to determine thermally stable ranges of SrO⋅2FeO⋅8Fe2O3(SrW) and SrO⋅FeO⋅7Fe2O3(SrX) compounds under various oxygen partial pressures. The existence of SrO⋅eO⋅7Fe2O3(SrX) compound was first verified in the present work.
Upper limits of the stability ranges for SrW and SrX compounds determined by XRD were found to be expressed as follows:
1) SrW compound
SrW=Magnetite+Liq.+O2
RTlnPo2=-227×103+128.5T (cal/mol O2)
2) SrX compound
SrX=SrW+Liq.+O2
RTlnPo2=-214.5×103+122.5T (cal/mol O2),
where Po2 is the oxygen partial pressure in atm unit, T is temperature in °C unit, and R is 1.9872 cal/(mol⋅K).
Ferrous contents of SrW and SrX compounds increased with increasing temperature and with decreasing oxygen partial pressure. No significant changes in saturation magnetization were observed with variation of ferrous contents of SrW and SrX compounds.View full abstractDownload PDF (481K) -
Naoichi Yamamoto, Yoshio Oka, Shigetoshi Muranaka1992 Volume 39 Issue 10 Pages 929-932
Published: October 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSCritical current value of Pbo.2Bi0.9Sr1.0Ca1.0Cu1.6Oy film was studied at liq.N2 temperature. It was found that silverclad was useful for enhancement of the critical current and the obtained maximum value (Ic) reached around 4A ( an equivaien Jc value of around 2000A /cm2).View full abstractDownload PDF (1539K)
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