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Volume 62, Issue 7
Displaying 1-13 of 13 articles from this issue
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Kuniteru Mihara, Takao Takeuchi, Hirowo G. Suzuki1998 Volume 62 Issue 7 Pages 599-606
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSEffect of Ti addition on the microstructure and mechanical properties of Cu-15 mass%Cr alloy was investigated. The main results are summarized as follows:
(1) Dislocations introduced by cold working were accumulated in the Cu matrix, which leads to the formation of band structure.
(2) Tensile strength of cold rolled specimen follows the Hall-Petch relation and was inversely proportional to the root square of thickness of Cu phase, d.
(3) Hardening by aging treatment occurs owing to the precipitation of Cr and Ti in Cu matrix and also to the precipitation Ti in Cr fiber.
(4) A linear relation between the tensile strength and hardness exits for the cold worked and aged specimens, but the linearity constant is quite different between them.
(5) A good combination of tensile strength higher than 1000 MPa and electrical conductivity higher than 70%IACS was obtained by cold working to η=6.9 and aging at 748 K for 1 h.View full abstractDownload PDF (3627K) -
Junji Saida, Yousuke Tanaka, Yasuji Tanaka1998 Volume 62 Issue 7 Pages 607-616
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSAmorphous Fe78Si9B13 alloy ribbons were joined by high voltage discharging at various pressures and input energies. The joined alloy ribbons have a high relative density of 93 to 98%. The interface among ribbons is melted partially by discharging , where we can confirm a halo pattern without any contrast revealing the existence of a crystalline phase by a transmission electron microscope observation prepared at the input energy of 0.6 kJ·g−1. Furthermore, the tensile fracture surface of the melted region has a vein pattern resulting from the final fracture process in amorphous structure, which is represented that even the melted part has an amorphous structure by requenching. The structure of the melted region changes to the crystalline phase with the increase of input energy. The halo pattern disappears in the melted region prepared at the input energy of 2.0 kJ·g−1 and the tensile fracture surface shows a shell pattern revealing the embrittlement by the crystallization. The crystallization process proceeds through a metastable phase which is a mixture of MS-I and MS-II phases above the input energy of 1.5 kJ·g−1. These two metastable phases are corresponding to a bcc structure and a complex ordered structure containing a large amount of metalloids. The DC soft magnetic properties and core loss at 60 Hz deteriorate drastically with the increase of input energy above 1.5 kJ·g−1, which is mainly due to the increase of hysteresis loss by joining of high voltage discharging under the applied pressure.View full abstractDownload PDF (3728K) -
Hiroyuki Masuda1998 Volume 62 Issue 7 Pages 617-620
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSPrevious AFM observation showed that small water droplets and water film were observed on the surface when pure water or aqueous solution was poured on graphite or mica. In this experiment, pouring pure water and 0.01 kmol·m−3 CuSO4+H2SO4 aqueous solution on graphite, adsorbed water observed by AFM was tried to detect by the FT-IR microscope. The existence of adsorbed water on the surface of gold and pure iron was also examined by the FT-IR microscope and AFM. The results showed that the peak of water was observed near 1590 cm−1 on the surface of graphite, gold and pure iron. The existence of liquid film of which thickness is 2 nm was confirmed by the AFM observation. From these results, there is the high possibility that the water film exists on the metal surface used for present experiment.View full abstractDownload PDF (1276K) -
Satoshi Emura, Masuo Hagiwara, Yoshikuni Kawabe1998 Volume 62 Issue 7 Pages 621-628
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSTi3Al-based alloys are attractive materials for aircraft and automobile parts because of their higher strength to weight ratio and higher Young’s modulus compared to those of conventional titanium alloys. In the present study, Ti3Al alloys containing large amounts of Nb were produced using a blended elemental (BE) powder metallurgy (P/M). Since high cycle fatigue strength is particularly important for industrial applications, special attention was paid to improve this property by the modification of microstructure.
Extra low chlorine titanium powder and Niobium-Aluminum master alloy powder were used as starting powder materials. Blended powders were cold pressed using mechanical pressing or cold isostatic pressing, vacuum sintered at 1573 K for 10.8 ks and finally hot isostatic pressed (HIP’ed) at 1373 K and 200 MPa for 10.8 ks. The compacts produced by this conventional method showed a coarse colony-like microstructure. A refined equiaxed α2 microstructure was obtained by the innovative BE P/M method, in which a water-quenching step is added prior to HIP’ing. Mechanism of the formation of an equiaxed microstructure was analyzed based on the observation of microstructural evolution during the HIP thermal cycle. Remarkable improvement of smooth high cycle fatigue strength was attained by this microstructural modification. For example, high cycle fatigue strength at 107 cycles increased to 440 MPa, from 340 MPa for conventionally processed materials.View full abstractDownload PDF (5684K) -
Masahiko Ikeda, Shin-ya Komatsu, Takashi Sugimoto, Kiyoshi Kamei, Kats ...1998 Volume 62 Issue 7 Pages 629-634
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThermal conductivity κ and electrical resistivity ρ of solution treated β Ti-V alloys were measured in two temperature ranges, near liquid nitrogen temperature (LN) and room temperature (RT), and compared to commercial purity Ti, high-purity Ti and austenitic stainless steel SUS304. The κ and also its temperature dependence of the β Ti-V alloys were smallest among all other alloys. In both temperature ranges, LN and RT, the ρ and κ of all alloys showed reciprocally proportional relations. According to the Wiedemann-Franz’s law, empirical relations between temperature T, resistivity ρ and thermal conductivity κ obtained for β Ti-V alloys were,
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\ oindentat room temperature and
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\ oindentfor temperatures between 83 and 85 K.View full abstractDownload PDF (918K) -
Toru Hinomura, Saburo Nasu, Yo Tomota1998 Volume 62 Issue 7 Pages 635-641
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSMagnetic properties of fcc γ-FeMn and hcp ε-FeMn alloys have been investigated as a function of Mn content by means of 57Fe Mössbauer spectroscopy. The γ-phase of Fe-Mn alloy is antiferromagnetic and shows a small hyperfine magnetic field at room temperature. The Néel temperature of γ-phase increases with increasing Mn content. The hyperfine magnetic field of γ-phase observed at 10 K also increases with increasing Mn content, and this suggests the increase in Fe magnetic moment in γ-FeMn alloy. The ε-phase of the FeMn alloy is also antiferromagnetic. However, the Mn content dependence of the magnetic property of ε-phase is quite different from that of γ-phase. With increasing Mn content of ε-phase from 14 to 20 mass%, the Néel temperature of ε-phase decreases from 235 to 157 K. In addition, ε-phase in Fe-24 mass%Mn does not show the antiferromagnetic order even at 10 K. The Néel temperature of ε-phase is found to decrease rapidly when the Mn content increases over 20 mass%. The hyperfine magnetic field of Fe in ε-phase observed at 10 K is quite small, about 1.0 T, and slightly decreases with increasing Mn content. This suggests that the magnetic moment of an Fe atom in ε-FeMn alloy is less than 0.1μB and decreases with increasing Mn content.View full abstractDownload PDF (1118K) -
Jong Soo Woo, Chan-Hee Han, Byung-Deug Hong, Jirou Harase1998 Volume 62 Issue 7 Pages 642-647
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSPrimary recrystallized Fe-3%Si specimens were nitrided and annealed with the heating rate of 15°C/h in 100% N2 atmosphere. With an increase in the heating temperature by 10°C, the heating was interrupted and the specimen was rapidly cooled and the magnetic induction B8 was measured and rapidly heated again to the heating temperature. Onset of secondary recrystallization was detected by the rapid rise of B8. B8 after secondary recrystallization was closely related with the onset temperature of secondary recrystallization (Tcr). The maximum B8 obtained was about 1.94 T when the Tcr was around 1075°C and the B8 decreased with increasing in the Tcr. The Tcr was closely related with the primary grain size and it was about 1075°C when the grain size was about 15 μm. The Tcr increased with increasing primary grain size and it was about 1100°C when the primary grain size was about 22 μm.
The same primary specimens were coated with MgO and annealed with the same heating rate in 5%H2-N2. The maximum B8 obtained was almost the same as the above annealing condition; however, the primary grain size for obtaining the maximum B8 was different in this annealing. The difference in the optimum grain size for obtaining the maximum B8 in both annealing methods was explained on the assumption that the maximum B8 is obtained when the Tcr is about 1075°C in both annealing methods.View full abstractDownload PDF (1135K) -
Sengo Kobayashi, Toshiyuki Koyama, Toru Miyazaki1998 Volume 62 Issue 7 Pages 648-652
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSA new characterization method of the microstructure utilizing the macroscopic compositionally gradient alloy was recently proposed by the present authors. The influence of macroscopic composition gradient on the formation of a microstructure is estimated either theoretically or experimentally in the present paper. The results obtained are as follows:
The theoretical investigation shows that the macroscopic composition gradient up to 10 at% per 1 μm dose not give any influence on the formation of microstructure.
The experimental examinations on the microstructural formation performed for the compositionally gradient alloy of 8.9 at% per 1 μm and the compositionally homogeneous specimen do not exhibit any difference in both microstructures.View full abstractDownload PDF (1502K) -
Koji Kakehi1998 Volume 62 Issue 7 Pages 653-661
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe stress-controlled fatigue tests were performed at 700°C. In this study, two kinds of fatigue testing procedures were adopted. One is the tension-compression triangle-waveform test (R=−1). The other is the tensile or compressive stress hold testing procedures. Cracks initiated at casting pores under tensile stress conditions. Only in compressive stress hold test, crack was initiated by stage I cracking (crystallographic cracking on the {111} slip plane). In [011] and [\bar111], the transition from mode I cracking (perpendicular to the principal stress axis) to mode II-type crystallographic cracking on the {111} slip plane was occurred easily because there were not enough non-co-planar slip systems in order to relax the stress concentration near the crack-tip.
The [001] crystals showed stable mode I crack growth because the stress concentration at crack-tip was relaxed by homogeneous multiple slip. The creep-fatigue damage mechanisms were found to be divided into two groups. In the case of the [001]-compressive and [011]-tensile stress hold waveforms, deformation occurred by mechanical-twin shear through γ and γ′. On the other hand, in the case of the [001]-tensile and [011]-compressive stress hold waveforms, each γ′ particle was sheared by superlattice partial with the fault bounded Shockley partial because the direction of shear stress on the (111) plane was opposite to that of microtwin formation. Fatigue lifetimes were decreased by the formation of deformation twinning.View full abstractDownload PDF (4914K) -
Kyu-Sang Cho, Hiroshi Takamatsu, Hiroshi Honda, Kenji Morinaga1998 Volume 62 Issue 7 Pages 662-668
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe effect of spinning condition on the quality of Fe77.5Si7.5B15(at%) wires produced by the In-Rotating-Water Spinning Method was examined experimentally. The diameter of the injection nozzle was 0.25 mm. Long continuous wires with round cross section were obtained when the molten-jet velocity νj was a little higher than the drum velocity νd, whereas the wire became meanderous with the increase in νj⁄νd. The heat of crystallization ΔH, which expresses the degree of non-crystallinity of the wire, remained almost constant for 0.77<νj⁄νd<1. For this case the wires were estimated to be almost amorphous judged from the X-ray diffraction pattern and the scanning electron micrograph. For 1<νj⁄νd<1.32, however, ΔH decreased with increasing νj⁄νd. The temperature distribution of the jet was measured by the photo-calorimetric method. For the water temperature of 10°C, the average cooling rate of the jet between 1470 to 1200 K, was found to be 6×104 to 9×104 K/s. The measured cooling rate did not show any correlation with ΔH. This indicated that the quality of the wire was determined by the cooling rate in the downstream region with a lower temperature.View full abstractDownload PDF (2223K) -
Masaaki Kato, Yoichi Nishino, Shigeru Asano, Shigeo Ohara1998 Volume 62 Issue 7 Pages 669-674
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSWe have measured the electrical resistivity and the Hall effect in D03-type (Fe1−xVx)3Al alloys with 0≤x≤0.38. When substituted by V, the electrical resistivity increases rapidly at low temperatures and shows an anomalous temperature dependence: an occurrence of a resistance maximum at or near the Curie point TC and a negative resistivity slope above TC. The tendency of the negative temperature dependence increases markedly with the V composition, accompanying a sharp drop in TC. In particular, the Heusler-type Fe2VAl alloy (x=0.33) exhibits a semiconductor-like behavior with an extremely large resistivity reaching 30 μΩm at 4.2 K. In parallel with the increase in resistivity at low temperatures, the Hall coefficient of the order of 10−8 m3/C also increases rapidly with the V substitution, suggesting a reduction in the carrier concentration.View full abstractDownload PDF (968K) -
Hirohisa Masuda, Naotaka Sakamoto, Kenji Morinaga1998 Volume 62 Issue 7 Pages 675-680
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSStructural parameter Mp based on the principle of madelung constant of ionic crystal was proposed to predict the medium-range structures of glasses using thermal expansion coefficients of them. The applicability of Mp was investigated with Mp-structure relationships of four kinds of typical oxide glasses: silicate, borate, phosphate and germanate. Consequently, the composition dependence of the glass structures, especially the basic unit polymerization, was exhibited well with Mp. It was evident that Mp was available as the medium-range structural parameter. The structure of antimonate glasses was presumed with Mp that it was not simple three-dimensional network and there was little change of the polymerization degree with network modifier content. Then, it was suggested that, in the case of an investigation of the glass structure, the structural parameter Mp makes possible to predict the composition dependence of medium-range structure, particularly the polymerization degree change.View full abstractDownload PDF (1004K) -
Masao Kosuge, Hideki Hosoda, Shuji Hanada1998 Volume 62 Issue 7 Pages 681-689
Published: 1998
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe pulverization by hydrogenation is a new method for fabricating intermetallic powders with high quality and low cost. In this study, the pulverization by hydrogenation was studied for various Nb-Cr alloys. The hydrogenation was performed under the hydrogen atmosphere of 0.1 MPa in an arc-melting chamber without exposure to air after arc-melting. Constituent phases and lattice constants before and after hydrogenation were examined by X-ray diffraction analysis. It is found that the pulverization by hydrogenation occurs only in two phase alloys consisting of Nb solid solution (Nbss) and NbCr2. In the Nbss/NbCr2 alloys, the lattice constant of Nbss increases remarkably through hydrogenation, while that of NbCr2 does not change. It is concluded that the pulverization of the Nbss/NbCr2 two phase alloy is caused by large strain accompanied with lattice expansion of Nbss through hydrogenation and crack nucleation at intrinsically brittle NbCr2.View full abstractDownload PDF (3190K)
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