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Volume 44, Issue 11
Displaying 1-18 of 18 articles from this issue
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Equo KOBAYASHI, Yoshinao MISHIMA1994 Volume 44 Issue 11 Pages 595-600
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
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Kenji MATSUDA, Sadao NISHIGHORI, Yukiya NAKAGAWA1994 Volume 44 Issue 11 Pages 601-603
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
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Yoshio ASHIDA1994 Volume 44 Issue 11 Pages 604-608
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
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Keizo HASHIMOTO1994 Volume 44 Issue 11 Pages 609-613
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
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Kazuhisa SHIBUE1994 Volume 44 Issue 11 Pages 614-621
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
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Yasuyoshi FUKUI, Noboru YAMANAKA, Yoshimi WATANABE, Yoshihiro OYA-SEIM ...1994 Volume 44 Issue 11 Pages 622-627
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSA thick-walled tube of an in-situ Al-Al3Ni functionally graded material (FGM) was made by the centrifugal method with an ingot of commercial purity Al-20 mass%Ni master alloy. The applied centrifugal forces, expressed by G numbers, are 23 and 147 times of the gravitational acceleration. The microstructure of the FGM tube consists of granular morphology Al3Ni as a second phase distributed within the aluminum matrix with an increasing volume fraction gradient from the inside to the outside of the tube. The shape of the Al3Ni particles varies from the spindle or needle to almost the rectangular or square while their sizes are dependent upon both their location in the tube thickness and the applied G number. The mean particle size is around 60μm. The Young's modulus and the linear expansion coefficient of the Al-Al3Ni FGM are found to vary from 72.9 to 117.2GPa and from 23.4×10-6 to 19.4×10-6/K, respectively, across the tube-wall thickness from the inner to outer surface reflecting the volume fraction change of the Al3Ni phase from 3 to 58 vol%.View full abstractDownload PDF (960K) -
Masahiko IWAI, Tomoaki HIROTA, Mitsuo NIINOMI, Toshiro KOBAYASHI1994 Volume 44 Issue 11 Pages 628-634
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSEffect of microstructure on tensile properties and fracture toughness of Ti3Al-Nb was investigated. The tensile properties and fracture toughness decrease with increase in the size of primary α2. The tensile strength increases with decrease in the volume fraction of primary α2 while the elongation and reduction of area decrease. The fracture toughness increases with decrease in the volume fraction of primary α2 when the volume fraction of primary α2 is between 8 and 17%. Decreasing cooling rate after solutionizing from water quenching to air cooling decreases tensile properties and fracture toughness in non-aged specimen because of the formation of transformed β during cooling. The tensile properties and fracture toughness decrease by aging because of the precipitation of α2 when the cooling rate is greater like water quenching after solutionizing. The tensile strength, elongation, reduction of area and fracture toughness increase by aging when the cooling rate is smaller like air cooling after solutionizing because the transfored β is divided into smaller pieces although 0.2% proof stress decreases.View full abstractDownload PDF (1640K) -
Hideyuki SAITOH, Takayuki SUGIMOTO, Hiroyuki IZUMI, Akihiko KIMURA, To ...1994 Volume 44 Issue 11 Pages 635-640
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSBehavior and suppression of environmental embrittlement in Co3Ti have been investigated by means of the small punch (SP) test, electrochemical measurements and tritium autoradiography. The environmental embrittlement in Co3Ti is the hydrogen embrittlement caused by the hydrogen generated from the humidity in air. The brittleness of Co3Ti is not the intrinsic nature but the extrinsic one arised from the environmental embrittlement. The environmental embrittlement can be suppressed when Co3Ti is in high vacuum or in dry air because there is free of moisture as a hydrogen source. The addition of Fe to Co3Ti is confirmed to be effective for the suppression of environmental embrittlement. The mechanism of the supression is to reduce a supply of hydrogen from the surface to the interior of Co3Ti due to the increase of hydrogen desorption rate resulting from the enhancement of hydrogen recombination.View full abstractDownload PDF (871K) -
Hiroshi SUZUKI, Yasushi YAMABAYASHI, Akira NOZUE, Tadatsune OKUBO1994 Volume 44 Issue 11 Pages 641-645
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSIntermetallic compound Al3Ti was fabricated by reactive sintering method. Elemental powders of Al and Ti with 73, 74, 75, 76 and 77 mol%Al were pressed and heated in a hot-pressing apparatus under a vacuum of 10-2Pa. Readily dense Al3Ti was obtained under a fabrication condition of the hot-pressing temperature, 1373K, and the pressing time, 60min. Microstructures of the sintered material were dependent on the nominal Al content: Aluminum content of 76 and 77 mol%Al showed grains of about 20-40μm, while 75, 74 and 73 mol%Al had fine gains of around 2-3μm and second phase particles of about 30μm.The second phase of 73 mol%Al consists of Ti3Al and TiAl, while that of 75 mol% Al consists of TiAl. The size and number of the second phase increased with decreasing the nominal Al content. The matrix of all sintered materials was the stoichiometric Al3Ti independent of the nominal Al content. Mechanical properties were measured by Vickers hardness and compression tests. The hardness and the compression strength showed maximum around 75 mol%Al, decreased at other compositions. The relations between the microstructures and the mechanical properties were discussed.View full abstractDownload PDF (805K) -
Hirofumi INOUE, Yasumasa YOSHIDA, Naotsugu INAKAZU1994 Volume 44 Issue 11 Pages 646-651
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe textures of the γ phase formed by isothermal forging at 1373K have been investigated in various TiAl-base alloys containing a small amount of the α2 phase using crystallite orientation distribution functions. The textures of 67% isothermally forged alloys consist mainly of the <100]//TD partial fiber component with a maximum peak in the vicinity of a {032)<100] orientation. However, the degree of texture development is remarkably influenced by the compositions of alloys. The addition of Mn as the third element and/or the decrease of the α2 content increase the intensity of the γ textures. From the results of microstructural observations, it is obvious that the texture formation during isothermal forging is closely related to dynamic recrystallization as well as slip rotation through compressive deformation. The formation of the {032)<100] texture may be explained by considering oriented nucleation and selective growth.View full abstractDownload PDF (1005K) -
Shigeo HATTORI, Akiyasu MORITA, Nobuyuki FUJITSUNA, Yoshiyuki MIYAMOTO ...1994 Volume 44 Issue 11 Pages 652-657
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSFundamental aspects of isothermal rolling technology were investigated in order to develop the manufacturing process of Ti-Al intermetallic compound sheet. The results of this investigation, in which a compression-test apparatus developed to simulate the isothermal rolling condition was used, suggest that SIALON is suitable as a roll material and that graphite is a good lubricant for the isothermal rolling at temperatures above 1273K. Based on the compression-test data, an isothermal rolling mill was newly designed and constructed. Ti-46at%Al sheet was rolled in this mill. The rolling pressure decreases and the formability of Ti-46%Al sheet is improved with increasing total reduction. The lamellar structure existing before rolling is destroyed with repeated rolling and a mixed structure of (γ+α2) grains is formed. It is possible to reduce the size of γ and α2 grains by optimizing the strain rate during multi-pass rolling.View full abstractDownload PDF (1224K) -
Masahiro INOUE, Katsuaki SUGANUMA1994 Volume 44 Issue 11 Pages 658-662
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe reactive sintering mechanism of Ni-Al powder mixture near NiAl stoichiometric composition was investigated. The reaction process of the powder mixture with Ni-rich composition has been found to consist of three stages; i. e., initial reaction leading to NiAl3 and Ni2Al3 formation (873-973K), liquid phase reaction induced by heat-releasing from the initial reaction (-973K) and homogenization (above 973K). The fully dense NiAl with the Ni-rich composition can be fabricated successfully by hot-pressing at 1573-1673K. In the case of stoichiometric and Al-rich composition, sintered bodies of full density can be hardly obtained by hot pressing even at 1773K, as the result of no rapid liquid phase reaction and of marked Kirkendall effect. The formation of eutectic liquid phase by self-heating in the initial stage and subsequent liquid phase reaction are essential for full densification of the Ni-Al compound system.View full abstractDownload PDF (1132K) -
Yasuhiro MIURA, Kei-ichi FUKUNAGA1994 Volume 44 Issue 11 Pages 663-668
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSExperimental study was carried out on high temperature mechanical behavior of L12-trialuminides, (Al, Cr)3Ti and (Al, Cu)3Ti. Focus was on the nature of the serrated flow which occurs in a relatively low temperature range at the critical strain. Serrated flow was observed during deformation in compression at temperatures as low as 473K. The critical strain for the onset of the serrated flow depends on strain rate and test temperature. Higher temperature or lower strain rate results in a smaller critical strain. A simple analysis of the data by the use of an equation based on the theory of dynamic strain aging by solute atoms gives an apparent activation energy smaller than 100kJmol-1 for both (Al, Cr)3Ti and (Al, Cu)3Ti alloys. The measured activation energy is much smaller than the reported activation energy for the diffusion of substitutional solutes in L12-trialuminides, implying that the diffusion of interstitial solutes is responsible. Possible diffusion process in ordered L12-(Al, X)3Ti alloys with low activation energy are discussed.View full abstractDownload PDF (699K) -
Masaki KUMAGAI, Kazuhisa SHIBUE, Mok-Soon KIM, Tsutomu FURUYAMA1994 Volume 44 Issue 11 Pages 669-674
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSWear resistance of reactive-sintered TiAl-Mn which was coated with oxide film was evaluated by pin-on-disk type wear test. Oxide film was coated by using oxidation reaction in air at 1173K. The two coated TiAl-Mn alloys show much less wear loss than uncoated ones. After wear test, oxide film remains partialy in the coated Ti-47.3Al-1.7Mn. On the contrary, oxide film of the coated Ti-43.2Al-1.6Mn is worn over. The low wear loss in the later is due to hard Ti-rich layer which is formed under oxide film produced during oxidation treatment. Thickness of Ti-rich layer increases with titanium content of TiAl-Mn or oxidizing temperature. It is supposed that Ti-rich layer is hardened by solutioning oxygen. Excellent wear resistance of the oxidized TiAl-Mn is caused by not only oxide film but also Ti-rich layer. This superior wear resistance surface can be obtained easily by oxidation in air of reactive-sintered TiAl-Mn containing chlorine.View full abstractDownload PDF (1783K) -
Hideki HOSODA, Tatsuo SATO, Hiroyasu TEZUKA, Yoshinao MISHIMA, Kanryu ...1994 Volume 44 Issue 11 Pages 675-681
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDefect structures and site-preferences of tenary elements in an off-stoichiometric transition metal Al3Nb-based trialuminides are predicted by the pseudo-ground state analysis based on the first nearest neighbor approximation. The calculated stable defect structures are structure-type (vacancy type) defect in Al-rich side and antistructure-type (substitution type) defect in Nb-rich side of stoichiometry. Additional elements that belong to VII a through V b group in the periodic table and Be are Al-site substitutions, and those that belong to I a through IV a group except for Be are Nb-site substitutions in any compositions. Moreover, a guide to alloy design of Al3Nb is also discussed.View full abstractDownload PDF (829K) -
Takehiko ETO1994 Volume 44 Issue 11 Pages 682-693
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
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Hisashi TAKEUCHI1994 Volume 44 Issue 11 Pages 694-695
Published: November 30, 1994
Released on J-STAGE: October 30, 2008
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1994 Volume 44 Issue 11 Pages vi
Published: 1994
Released on J-STAGE: October 30, 2008
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