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Volume 59, Issue 4
Displaying 1-15 of 15 articles from this issue
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Toshio Mukai, Yoshiharu Inoue1995 Volume 59 Issue 4 Pages 359-365
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCold-rolled foils of pure iron are tested for recrystallization in various atmospheres. The (100) orientation is produced by annealing in non-oxidizing atmospheres through secondary recrystallization; grains with (100) planes at the gas-metal interface grow at the expense of other (211) grains. It has been found for the first time that the (100) orientation develops faster in a N2/H2 mixed gas atmosphere than in a pure H2 atmosphere. Observation using an oxidation tinting method clearly revealed that the number of (100) secondary nuclei is increased under nitrogen-annealing. The result is dicussed in terms of the surface energy difference altered by nitrogen adsorption.
The texture of complete (100) orientation has been achieved by annealing in a pure N2 atmosphere with oxygen content less than 0.01 vol ppm. The easy magnetization direction of the (100) oriented foil was found to be oriented 45 degrees away from the rolling direction.View full abstractDownload PDF (1314K) -
Takashi Yoshikawa, Fukuji Inoko1995 Volume 59 Issue 4 Pages 366-372
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to clarify the effect of activated slip systems on recrystallization along a grain boundary, two kinds of 99.999 mass% silver bicrystal specimens which have the same grain boundary and different tensile directions were prepared. When they were deformed in tension to a strain of 0.3, the grain boundaries were changed into different ones with different structures because of the operation of different slip systems. After annealing, recrystallized grains were formed mainly through twinning and sometimes through the ⟨111⟩ rotation mechanism, along the grain boundary toward which dislocations with a large screw component pile up.View full abstractDownload PDF (1314K) -
Kohsaku Ushioda, Hirowo G. Suzuki, Hajime Komatsu, Kazuyoshi Esaka1995 Volume 59 Issue 4 Pages 373-380
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of sulfur on AlN precipitation during cooling after solidification and hot ductility was investigated in low carbon aluminium killed steels by means of a Gleeble tester together with chemical analysis and analyitical TEM. 1) The precipitation kinetics of AlN is very slow in austenite, but it is promoted with the addition of sulfur. 2) In the steels bearing sulfur, MnS precipitates first in austenite grain boundaries followed by the AlN precipitation, which preferentially takes place on MnS. The following orientation relationship was found between the two precipitates: (1\bar11)MnS\varparallel(0001)AlN, [110]MnS\varparallel[2\bar1\bar10]AlN and [121]MnS\varparallel[10\bar10]AlN. 3) This coherent heterogeneous precipitation was inferred to stem from the fact that the condition for the heterogeneous nucleation, which holds when the contribution of interfacial energy is large, was satisfied due to the relatively low interfacial energy of AlN/MnS as compared with that of γ-Fe/MnS. 4) The embrittlement of slabs during CC-DR (Continuous Casting-Direct Rolling) becomes understandable when the present result of AlN precipitation is superimposed in the convetional time-temperature embrittle curve. Namely, hot ductility becomes poor under the condition of the complex precipitation of MnS and AlN.View full abstractDownload PDF (1242K) -
Shigeru Kuramoto, Goroh Itoh, Motohiro Kanno1995 Volume 59 Issue 4 Pages 381-388
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTensile tests are performed at 77 K and 4.2 K for the Al-4.5%Zn-1.5%Mg(−1%Cu) alloys containing manganese, zirconium or chromium and the effects of these additives on ductility at low temperatures are studied in the microstructural aspects. Such transition elements have low solubility in aluminum and precipitate as dispersoids during ingot preheat. Dispersoids have a strong effect on the process of recovery or recrystallization during solution heat treatment and therefore on the mechanical properties of the final product at room temperature. In the present paper, the alloys containing zirconium or chromium, having unrecrystallized grain structure, exhibit higher ductility at 77 K than the alloy containing manganese, which has completely recrystallized. At 4.2 K, however, no appreciable difference in ductility is found among three additions. This can be explained in terms of localized deformation accompanied by serration that is characteristic of the deformation below about 40 K. Besides the mechanical behavior in parent material, the low temperature tensile properties in welded joints are also examined for these materials.View full abstractDownload PDF (1526K) -
Yoshimasa Takayama, Tatsumi Tozawa, Hajime Kato, Katsuo Matsumoto, Nor ...1995 Volume 59 Issue 4 Pages 389-394
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSuperplastic characteristics of a 7475 aluminum alloy have been evaluated by the R-type specimen method. The R-type specimen has no ordinary gauge part with a uniform cross section. The method has been proposed recently to solve the problems on the conventional tensile test using an ordinary specimen. As a result, it is found that the R-type specimen method enables to evaluate the extremely high superplastic elongation of the commercial 7475 alloy using a furnace with a common length. The elongation of the R-type specimen decreases with an increase in the radius of the R-part below a certain value, while it increases over that value. Better reproducibility of the elongation for the R-type specimen is obtained in Region II than that for the ordinary specimen. Moreover, the elongation of the ordinary specimen can be estimated quantitatively from the peak value of the strain distribution of the R-type specimen after fracture, using the suitable shape of the specimen and the adequate distance between gauge marks.View full abstractDownload PDF (519K) -
Takaaki Hatano, Toshiaki Yano, Naritoshi Kimura, Michiharu Yamamoto, M ...1995 Volume 59 Issue 4 Pages 395-402
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDesulfurizing experiments were conducted at 1473 K for a molten Cu-8%Sn-0.1%P alloy by using a Na2CO3 flux in low freqency melting furnaces. Desulfurization and dephosphorization began simultaneously. Desulfurization ceased earlier than dephosphorization and then the reversion of sulfur was found proceed. The use of carbon crucible promoted desulfurization and suppressed the reversion of sulfur more strongly compared with the use of an alumina crucible. Sulfur distribution between the melt and the flux was found to be determined by two major factors. One is the basicity of the flux, being affected by P2O5 content in the flux. The other is the partial pressure of oxygen at the interface between the melt and the flux, being affected by furnace materials, covering materials and Cu2O content in the flux. The desulfurization rate was explained quantitatively by a double interface model assuming mass transfer coefficient in the melt as 1.82 g·cm−2· s−1 and that in the flux as 0.063 g·cm−2· s−1. Dephosphorization and the influence of Cu2O content in the flux were also investigated.View full abstractDownload PDF (637K) -
Kenichi Kaneko, Koji Hayashi1995 Volume 59 Issue 4 Pages 403-407
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAccording to a hypothesis of the mechanism for varistor characteristics of semiconductor ZnO-base ceramics, i.e., current can easily flow only at high voltage through intergranular thin layers which are formed by the addition of Bi2O3 with high electrical resistivity (ρ), it was expected that non-linear voltage (V)-current (I) characteristics can appear in conductor Al powder sintered compacts, along grain boundaries of which thin layers of Al2O3 with high ρ are arranged. In this study, flaky Al powder (2.69 mass%O) compacts with the size of φ10 mm×t1∼4 mm and with the relative density of 85% were sintered at 673 K for 3.6 ks in vacuum and their V−I characteristics were measured in the range of 10−6∼2×103 V.
The results obtained are as follows: The current at low voltage was less than 10−7 A, i.e., the electrical resistivity of the compacts was very high (ρ >5×106 Ω·m), and the current non-linearly sharply increased up to 10∼103 A over a critical voltage (breakdown voltage, VB) of 50∼130 V, although a breakdown of air accompanied. However, the compacts became in general nearly ohmic conductor (ρ=10−3∼10−1 Ω·m) and VB disappeared, once the voltage higher than VB was applied. Namely, the flaky Al powder sintered compacts were clarified to have a unique V−I characteristics which is initially non-linear, and then becomes nearly ohmic after one application of high voltage.View full abstractDownload PDF (826K) -
Satoru Ohno, Hideo Okuyama, Kazuhiro Honma, Kazunori Takagi, Toshio Ho ...1995 Volume 59 Issue 4 Pages 408-414
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe possibility of synthesis of ultrafine particles (UFP) of iron nitride has been investigated by arc melting, vaporization and condensation of iron in atmospheres of N2-H2-Ar and NH3-Ar mixed gases (“reactive plasma-metal” reaction) at 0.1 MPa pressure. The crystal structure, morphology and nitrogen content of obtained UFP were determined by X-ray diffractometry, transmission electron microscopy and chemical analysis, respectively.
The crystal structure of UFP obtained in N2-H2-Ar atmospheres was found only single phase of α-Fe. In NH3-Ar atmospheres, the crystal structures of obtained UFP were the iron nitride phases of γ′-Fe4N and Fe3N and the nitrogen-austenitic phase of γ-Fe besides the α-Fe phase. The iron nitrides content of the UFP prepared in NH3-Ar atmospheres increased with decreasing NH3 concentration in the atmosphere, and in the case of NH3 concentration less than about 30 vol%, UFP of approximately γ′-Fe4N single phase were obtained.
From the above results, it is presumed that NH3 is most effective species for nitriding of iron vapor and/or condensed iron particles, and its nitriding zone is not within the arc plasma, but within the condensation region of iron vapor (formation region of UFP) around the arc plasma. On the basis of the conclusion, a newly designed apparatus for the production of iron nitride UFP has been developed with successful results.View full abstractDownload PDF (1178K) -
Toshio Shimoo, Takuya Yamazaki, Kiyohito Okamura1995 Volume 59 Issue 4 Pages 415-422
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe products derived from the reaction between Si3N4 and Fe-Ni alloy have been investigated. Si3N4-alloy powder mixtures were isothermally heated under a N2 or Ar atmosphere at temperatures from 1123 to 1573 K. The reaction products were examined by X-ray diffraction.
At low temperatures, Fe-Ni-Si solid solution was produced and the lattice constant of γ-phase decreased from 0.3591 to 0.3565 nm. At high temperature and on prolonged heating, silicides were formed by the disappearance of γ-phase. Prior to the occurrence of the iron silicide, nickel silicide was formed. Under the N2 atmosphere, Ni3Si was slightly produced at 1323 K and disappeared at 1373 K. Under the Ar atmosphere, Fe5Si3 and FeSi were produced in addition to Ni5Si2, Ni2Si and Fe3Si which were the reaction products under the N2 atmosphere, whereas the nitrides of Fe and Ni were not detected even under N2.View full abstractDownload PDF (774K) -
Masaki Kumagai, Kazuhisa Shibue, Mok-Soon Kim1995 Volume 59 Issue 4 Pages 423-428
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of aluminum content in TiAl-Mn containing a small amount of chlorine on the oxidation behavior has been studied in air over the temperature range from 1223 K to 1473 K. In this work, the alloys were prepared by using the reactive-sintering process.
The reactive-sintered TiAl-Mn alloys have excellent oxidation resistance in the temperature regions of γ and γ+α2 phases compared to the cast one, owing to the formation of a protective thin Al2O3 scale due to chorine. However, the TiAl-Mn is oxidized drastically over the eutectoid temperature, 1398 K. In α2 region the oxidation behavior of the reactive-sintered TiAl-Mn is similar to that of the cast one. The oxidation resistance region in the equilibrium phase diagram is shown for the reactive-sintered TiAl-Mn containing a small amount of chlorine.View full abstractDownload PDF (2056K) -
Hiroyuki Morimoto, Masahiro Nomura, Yoshio Ashida1995 Volume 59 Issue 4 Pages 429-436
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAn attempt was made to fabricate in-situ TiC particulate reinforced aluminum composites (TiCp/Al) utilizing the reaction between graphite particles and liquid Al-Ti alloy. Induction furnace equipped with a stirrer was used in order to make it possible to fabricate composites with a high TiC particle volume fraction. TiC particle formation was observed above 1300°C. The size of TiC particles dispersed in the composites was 0.2∼4 μm and increased with the processing temperature. 10 and 20 vol%TiCp/Al with uniform particle dispersion were successfully fabricated, by suppressing of formation of Al3Ti and Al4C3 and stirring of the melt. TiC particle formation behavior around the interface between graphite and liquid Al-Ti alloy was studied by FE-SEM observation and Auger electron spectroscopy analysis. At an early stage of reaction, 0.2∼0.5 μm TiC particles formed on the surface of graphite and then dispersed into the melt. At a late stage of reaction, the Al4C3 phase with about 1 μm formed on the surface of graphite. The Al4C3 phase decomposed to form TiC particles at about 1 μm distances from the graphite surface. Such a TiC formation behavior was discussed from the thermodynamical viewpoint considering the activity of Ti in the liquid Al-Ti alloy. Young’s modulus and tensile strength of TiCp/Al increased proportionally with the TiC particle volume fraction. The Young’s modulus of 20 vol%TiCp/Al was so high as 104 GPa, being equivalent to that of 20 vol%SiCp/Al fabricated with a powder metallurgical process.View full abstractDownload PDF (1671K) -
Tadashi Fukuda, Hiroshi Suenaga, Mitsuru Tanino1995 Volume 59 Issue 4 Pages 437-446
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEffects of morphology of carbide and nitride precipitates on the ductility of Fe-30 mass%Cr alloys containing C from 0.002 to 0.044 mass% and N from 0.004 to 0.13 mass% were investigated. Three kinds of processes including heat treatments and cold rolling were adopted to obtain different types of morphology of carbide and nitride precipitates. Tensile tests were carried out at temperatures ranging from 4.2 K to room temperature. Ductility was evaluated by transition temperatures in reduction of area.
The results obtained are summarized as follows:
(1) Aging after solution-treatment gives rise to grain boundary precipitation of raft-like carbide or continuous plate-like nitride, while annealing without solution-treatment produces coarse globular carbide particle (5 μm) or fine spheroidal nitride particle (≤0.5 μm) within the grains. Aging after cold rolling of solution-treated specimen produced fine spheroidal carbide particle (≤0.5 μm) within the grains.
(2) Even a small amount of plate-like grain boundary nitride brings about a drastic increase in transition temperature. Initiation of microcracks for brittle fracture may be caused by decohesion at the interfaces between the matrix and grain boundary precipitates, due to their continuous flat plate-like morphology. On the other hand, the effect of raft-like grain boundary carbide is less remarkable than grain boundary nitride.
(3) Fine spheroidal nitride and carbide particles within the grains do not exert any detrimental effect on transition temperature, while coarse globular carbide leads to moderate increase in transition temperature.
(4) In order to obtain improved ductility, it is recommended to choose a process condition in which precipitates are dispersed as fine particles within the grains.View full abstractDownload PDF (2328K) -
Terumi Tanaka, Hitosi Arimura, Sin Kikuchi, Satoru Sugimoto, Masuo Oka ...1995 Volume 59 Issue 4 Pages 447-455
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe magnetostrictive properties of (Tb, Dy)-Fe-B alloys with fine (Tb, Dy)Fe2 grains crystallized from an amorphous state were studied.
Amorphous phases were obtained for rapidly quenched ((Tb1−xDyx)0.33Fe0.67)100−yBy alloys with B content over 5 mol%.
Increasing of Dy content makes the alloys easy to be crystallized during rapidly quenching process, and then it is necessary to increase the B content for achieving an amorphous state.
Annealing of amorphous alloys gives a finely crystallized grains of RFe2 compound with the size of around 10 nm, which yields the high magnetostrictive susceptibility and low coercive force.
Maximum magnetostrictive susceptibility, (dλ/dH)H=0.1=55.8×10−10(m/A), of ((Tb1−xDyx)0.33Fe0.67)100−yBy alloys was obtained in x=0.3 and y=6. This alloy exhibited the giant magnetostriction, λH=1.28=722×10−6 at the applied magnetic field of 1.28 MA/m.View full abstractDownload PDF (1529K) -
Hideki Iba, Etsuo Akiba1995 Volume 59 Issue 4 Pages 456-462
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAB2 type Laves phase and BCC solid solution have been investigated as the next generation hydrogen absorbing alloys with high capacity. We have proposed a new concept of alloy design named “Laves-phase related BCC solid solution” in the previous work.
The observations of microstructure show that Zr0.5Ti0.5VMn consisted of three phases; matrix C14, gray colony BCC and black particle Zr in the previous report. In this work we investigated each phase in detail by the combination of transmission electron microscopy and X-ray Rietveld analysis.
The composition of the matrix Laves phase is found to be Zr0.6Ti0.4V1.1Mn0.9 by TEM-EDX. The bright field image of this region is homogeneous and the electron diffraction pattern shows only the C14 structure. We consider that this phase is the Laves phase in which the A site is occupied by Zr and Ti and the B site is occupied by Mn and V. This atomic ratio of matrix is a stable composition of the phase which is contained in Zr-Ti-Mn-V alloys and is made by arc melt casting process.
The gray colony BCC phase in Zr0.5Ti0.5MnV decomposes into two nano scale phases that are Mn solute Ti-rich and V-rich phases. The lattice strain of two coherent phases show the satellite spots in electron diffraction and asymmetric peak broadening in X-ray diffraction patterns.
Black particle Zr phase is found to be α-ZrO2 by analysis of the electron diffraction. This oxide particle consists of two regions which have the same zone axis.View full abstractDownload PDF (674K) -
Akiko Yamamoto, Takeshi Kobayashi, Norio Maruyama, Kouzou Nakazawa, Ma ...1995 Volume 59 Issue 4 Pages 463-470
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPlain and fretting fatigue tests of an annealed Ti-6Al-4V alloy were carried out in ca. 150 mL of a pseudo-body fluid. A phosphate-buffered saline without calcium and magnesium salts (PBS(−)) was used as a pseudo-body fluid, and nitrogen gas was bubbled into the saline during the tests in order to reduce the concentration of dissolved oxygen in the saline. The fretting fatigue strength in PBS(−) was lower than those in the air at higher and lower stress amplitudes ranges, while the fatigue strengths in both environments were almost equivalent to each other.
Released metallic ions and debris in PBS(−) recovered after fretting fatigue tests under condition A (the stress amplitude, σa is set at 250 MPa) and B (σa is set at 131 MPa) were quantitatively analyzed by graphite furnace atomic absorption spectrophotometry (GFAAS). Before the analysis, some volume of the recovered PBS(−) were filtered through a 0.22 μm pore size filter. The unfiltered fluid of condition A contained iron, manganese, nickel, vanadium, chromium, aluminum and titanium in 42, 110, 110, 130, 970, 1150 and 2420 ppb (μg/L), respectively. Nickel, iron, aluminum and manganese in 24, 4, 3 and 2 ppb, respectively, were found in the filtered fluid of condition B, suggesting that corrosion by passive-active cell occurred between the fresh surface of crack-tips or fretting area and other surface covered by oxide films during the fretting fatigue test.
Cytotoxicity of the fluids of conditions A and B was investigated using MC3T3-El cells. Both of the filtered and the unfiltered fluids of the condition B were toxic for the cells, but only the unfiltered fluid of the condition A were toxic for the cells. These facts suggest that metallic substances in small concentrations as 10 ppb have cytotoxicity, and that not merely the amount but also the state of metallic elements affect the extent of cytotoxicity of the fluids.View full abstractDownload PDF (817K)
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