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Volume 60, Issue 11
Displaying 1-17 of 17 articles from this issue
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Hiroshi Fujita, Takefumi Tsuboi, Katsuyuki Harada1996 Volume 60 Issue 11 Pages 1031-1036
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAn electron microscope study has been carried out on the crystallization processes of amorphous aluminum- and iron-base alloys with the following results: 1) The nucleus sizes of both primary crystals are almost constant in a wide temperature range more than 100 K. 2) Lattice constants of both primary crystals are gradually changed until the crystallization is finished, i.e., it increases in the Al-alloy and decreases in the Fe-alloy. 3) The size of primary crystals becomes about φ10 nm in both alloys after crystallization, and do not grow until the secondary phases are precipitated. 4) They grow further to φ50∼100 nm at 573 K in the former specimens and at 973 K in the latter ones. After that, there is no remarkable change in their size in a temperature range of 100∼150 K higher than these temperatures.
The results are discussed in terms of the effect of guest elements exhausted from the primary crystals.View full abstractDownload PDF (1583K) -
Hiroshi Fujita, Takefumi Tsuboi, Katsuyuki Harada1996 Volume 60 Issue 11 Pages 1037-1042
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAluminum- and iron-base amorphous alloys were crystallized by isochronal annealing, and their mechanical properties were measured as a function of the grain size. The results obtained in both alloys are summarized as follows: 1) The tensile strength shows the maximum value when the 20∼30 vol% of the specimens is crystallized. By further annealing, these alloys become very brittle, and the strength abruptly decreases. The strength, however, increases again when the grain size reaches 50∼100 nm in diameter. 2) In these brittle materials, the effect of grain size on the strength was estimated by comparing the maximum tensile strength with microhardness. 3) Microhardness increases up to the maximum value when the specimens are fully crystallized with grains of 10 nm in diameter, and then gradually decreases with increasing grain size. 4) The alloys with grain sizes 50∼100 nm in diameter are thermally stable, and show the strength higher than those of the amorphous alloys.
The mechanical properties of both alloys are discussed as a function of grain size which is closely related with guest elements exhausted from the primary crystals.View full abstractDownload PDF (558K) -
Keiji Funaki, Shin-ichi Orimo, Hironobu Fujii1996 Volume 60 Issue 11 Pages 1043-1050
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe C15 Laves phase YNi2, which becomes amorphous YNi2Hx by hydrogenation, was mechanically ground under various hydrogen partial pressures up to 1.0 MPa to investigate the effect of the mechanical grinding (MG) on the hydrogen-induced amorphization (HIA) processes. Furthermore, the phase separation processes during dehydriding reaction were also examined. The results obtained are summarized as follows. Under the initial hydrogen pressure of 1.0 MPa, a single phase of amorphous YNi2Hx is observed by grinding only for 180 min, while such an amorphization can hardly occur even after hydrogenation for 10080 min without grinding. However the thermal stabilities of the amorphous phase and the dissolved hydrogen do not change by MG. On the other hand, when ground under the initial partial hydrogen pressure of 0.2 MPa, YNi2Hx is separated into two phases. The one is the α-phase, in which the solubility of a hydrogen is larger than that obtained by hydriding YNi2 without MG under the same condition, and the other is the α′-phase. The solubility of a hydrogen in α-phase gradually decreases with increasing the MG time, while the α′-phase is transformed into the amorphous phase upon further grinding. After grinding it for 1080 min, the α-phase is changed into YNi5. Excess Y left in the phase transformation will be dissolved into the amorphous phase and it will react with hydrogen to form YH2. These differences of the amorphization processes depending on the initial hydrogen pressures can be understood by considering the free energy variation in each phase by MG.View full abstractDownload PDF (825K) -
Naoki Maruyama, Ryuji Uemori, Yoshio Terada, Hiroshi Tamehiro1996 Volume 60 Issue 11 Pages 1051-1057
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe distribution and precipitation of Nb atoms at an very early stage of recovery and recrystallization in hot-deformed austenite were investigated by using an atom-probe field-ion microscope (AP-FIM) and a transmission electron microscope (TEM). The results were summarized as follows: 1) Solute Nb in austenite can delay the onset of recovery and recrystallization. 2) Solute Nb has the strongest retarding effect for recovery and recrystallization among the micro alloying elements; i.e., Nb, Ti, V, Mo. This seems to be caused by the strong interaction between Nb atom and vacancy or dislocation. 3) Nb-N substitutional-interstitial atom pairs were also detected in hot-deformed austenite. This may play an important role in the retarding effect of the early stage of recovery and recrystallization by strongly interacting with dislocations.View full abstractDownload PDF (1274K) -
Masayuki Tabuchi, Kenzaburo Marukawa, Kazuyoshi Takezawa1996 Volume 60 Issue 11 Pages 1058-1063
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe mechanism of the bainitic transformation in copper-based alloys has been in a long-standing controversy, because a contribution of lattice shearing to the transformation has been suggested or questioned by different researchers. In order to clarify the role of lattice shearing, the transformation process under applied stress at various temperatures between 423 and 473 K was traced in a Cu-Zn-Al alloy by measuring the electrical resistivity. Since the resistivity increases with increasing amount of transformation products, a quantitative evaluation of transformation kinetics can be made by this method. It has been found that the transformation is highly sensitive to the aging temperature, and that the activation energy is close to that of solute diffusion in the alloy. It is also evident that the applied stress accelerates the transformation, while it does not affect the activation energy. This acceleration clearly indicates that the transformation proceeds by lattice shearing. It is concluded that diffusion-controlled lattice shearing is the most plausible mechanism of the bainitic transformation. The effect of applied stress on the transformation rate is discussed in terms of the free energy change due to stressing.View full abstractDownload PDF (799K) -
Koji Tanoue, Kenji Furuta1996 Volume 60 Issue 11 Pages 1064-1071
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe shape of abnormal grains has a decisive effect on the grain boundary fracture at room temperature and the characteristics of creep at high temperatures in P/M tungsten fine wires. The effects of the amounts and distributions of bubbles in a material on it are therefore investigated using a Monte Carlo computer simulation technique. The abnormal grain growth initiating from the surface of a specimen can be simulated with a more dense distribution of the nuclei for abnormal grains near the surface, giving the microstructural time evolution similar to the structural change in a wire. The microstructure obtained presents several features as follows: (1) Some of abnormal grains with the nuclei of large size tend to survive after the others vanish during their growth. (2) A largest abnormal grain existing up to the final stage increases its size as the number of the nuclei for abnormal grains decreases. (3) The abnormal grain growth is accelerated when the primary one is strongly inhibited by the pinning force due to bubbles. It can be concluded from these results that the interlocking grain structure results mainly from the shape of the grains which is produced when the abnormal grains break away from an array of bubbles in various ways.View full abstractDownload PDF (752K) -
Yoshito Takemoto, Moritaka Hida, Akira Sakakibara1996 Volume 60 Issue 11 Pages 1072-1078
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe formation mechanism of {332}⟨113⟩ twin, one of the deformation modes in metastable β type titanium alloys, was examined by high resolution transmission electron microscopy (HR-TEM) and simulation. The interface structure of twin resembled to α″ martensite. Peculiar movement of atoms to form {332}⟨113⟩ twin was explained by the β→α″ process followed by the α″→β twin inverse transformation process. The former process brought about convenient conditions to form {332}⟨113⟩ twin; the atom displacement direction was parallel to ⟨113⟩, habit plane agreed with {332}, shear strain was 0.2907 and volume change was 0.4% expansion. The parameters of α″ obtained by calculation were a=0.3050 nm, b=0.4913 nm and c=0.4596 nm. Subsequently α″→β twin inverse transformation generated by a shear strain of 0.0628 results in {332}⟨113⟩ twin having a shear strain of 0.3535. It was suggested that atom displacement and compressive stress field with the martensitic transformation would yield a single ω variant or many defects in the twin band.View full abstractDownload PDF (845K) -
Shigenobu Ogata, Hiroshi Kitagawa1996 Volume 60 Issue 11 Pages 1079-1083
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe atomic structure and properties of an interface between aluminum-nitride ceramics (AlN) and aluminum (Al) has been studied using the first principle molecular dynamics (Car-Parrinello method) which is based on local density approximation to density-functional theory (LDA-DFT). A simulated annealing calculations are performed on two types of AlN(0001)/Al(111) models which possess different stacking sequences of Al layers. The effects of interface to atomic structure and electron distribution are localized and no extensive interfacial reaction can be found. The interfacial stiffness (force constant) is found to be comparable to that of pure Al(111) layers. The estimated interface adhesion energy which represents a kind of interface strength is consistent with the surface energy of Al(111).View full abstractDownload PDF (468K) -
Yukio Inokuti, Kazuhiro Suzuki, Osamu Ohkubo1996 Volume 60 Issue 11 Pages 1084-1089
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to clarify the crack morphology of TiN and Ti films on stainless steel sheets, it was undertaken to do high-speed plasma coating on wide and large materials under a high evaporation rate of 5 μm/min and high ionization of 75%.
After the bulge press-forming, there were no apparent peeling of the TiN and Ti coated layers and no obvious difference in surface integrity at the central and corner areas.
In the scanning electron microscopic observation, the TiN films at the central area showed the comparatively sharp straight cracks characteristic of ceramics. In contrast, the Ti films cracked in the slightly elongated manner characteristic of metal, with scribing on the surface due to the soft Ti film.
In the cross-sectional observation of TiN films, TiN films cracked perpendicular to the steel surface. In contrast, the Ti films opened at the surface and the steel sheet was masked in place by the Ti films.
In the corrosion test of these films, the TiN films were more susceptible to corrosion than the Ti films, presumably because the cavities created by internal peeling in TiN films exposed a greater area of steel and tended to trap corrosive substances.View full abstractDownload PDF (1374K) -
Shozo Inoue, Hitoshi Uchida, Atsushi Hioki, Keiji Koterazawa1996 Volume 60 Issue 11 Pages 1090-1094
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTiN films have many useful properties such as extreme high microhardness, resistance to wear, resistance to friction, and so on. However, relatively poor resistivity against oxidation is shown at high temperature. The purpose of this work is to investigate the oxidation behavior of the AlN/TiN double layer films as an alternative to TiN films.
TiN single layer films (thickness; 300 nm) and AlN(100 nm)/TiN(200 nm) double layer films were deposited onto (001) Si wafers using rf reactive sputtering apparatus with two planar magnetron type cathodes. The targets were pure Ti (>99.9%) and pure Al (>99.999%) disks (70 mm in diameter). An Ar+N2 mixed gas (Ar:N2=1:1, total pressure 0.4 Pa) was used as the sputtering gas. The substrate temperature and rf power were kept constant at R.T. and 300 W, respectively. The deposited films were annealed in the air environment at 400∼700°C for 60 min and then subjected to Auger depth profiling.
The as-deposited AlN/TiN interface appeared to be free from contamination and interdiffusion. There was no evidence of the existence of compound formation at the interface. X-ray diffraction analysis revealed that the AlN crystalline layer had an 00·2 preferred orientation on the weakly 001 oriented TiN layer. The oxide layer of ∼200 nm was formed on the TiN single layer films by annealing at 600°C for 60 min. On the contrary, the AlN/TiN double layer films showed excellent oxidation resistance even when annealing at 700°C.View full abstractDownload PDF (635K) -
Makoto Yoshida, Toshinori Muramatsu, Jia Fu Hong, Hideo Nakae1996 Volume 60 Issue 11 Pages 1095-1100
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSUndercooling and solidification phenomena of Cu and Cu-O and Cu-S alloys were investigated. The “one-way nucleation” of Cu/Cu2S eutectic was also examined. The undercooling of Cu-O and Cu-S alloys increased with increasing oxygen or sulfur content. This may be caused by oxidation or sulfurizing of effective nucleants in molten copper, or by the surfactant roll of oxygen and sulfur. Regarding the “one-way nucleation”, the Cu phase nucleates the Cu2S phase at small undercooling, but the Cu2S phase does not nucleate Cu.View full abstractDownload PDF (959K) -
Osamu Yanagisawa, Ahmad Almansour, Kazuhiro Matsugi, Tomei Hatayama1996 Volume 60 Issue 11 Pages 1101-1107
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA model to predict the solidification of spheroidal graphite (SG) cast iron during the cooling process was developed. Using the model, we treated the problem of the ternary Fe-C-Si system and aimed at simulating the evolution of the solidifying microstructure. When the eutectic temperature was reached, eutectic grains were formed. The rate of nucleation depended on the melt characteristics and supercooling. The nucleation rate was assumed to be presented by power law function of undercooling. The growth of the austenite grain was controlled by carbon diffusion through austenite. Carbon and silicon concentrations at different interfaces were calculated from the Fe-C-Si equilibrium ternary phase diagram and the Scheil equation was applied to calculate the silicon content in the bulk liquid and the concentration of carbon in the liquid was determined to keep the eutectic reaction.
The model was applied to a cylindrical sand casting with four-step diameters of 10, 20, 30 and 40 mm. The simulated results were compared with the experimental ones using a post processing program which was also developed to simulate the microstructural evolution graphically. The results showed relatively good agreement and the usefulness of the proposed model was confirmed.View full abstractDownload PDF (700K) -
Yasuhiro Maeda, Daigo Sugiyama, Hiroyuki Nomura1996 Volume 60 Issue 11 Pages 1108-1115
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe metal Injection Molding (MIM) process is a key technology which makes it possible to form the complicated parts with a near-net shape. MIM includes several elemental processes such as powder mixing, injection molding, debinding and sintering. Therefore, it is necessary to optimize those processes in order to obtain the sound final products. However, the technology of MIM has not been well established yet, although laboratory work on MIM has been carried out extensively by several researchers.
In this study, the optimum injection process which is a very important stage for making perfect products has been investigated by changing the forming conditions such as injection pressure, temperature of slurry material and composition of pellet. A stainless steel SUS304 powder which is widely used for a lot of major products is selected as the experimental material. On the basis of the obtained experimental facts, the optimization is done for the injection process in which defects are not left in the green compacts and the injection is done with the lowest energy. Furthermore, a numerical simulation is executed for the slurry filling behavior using Flow Analysis Network(FAN) method. According to the calculated results, the location of weld line, the arrival time of slurry and the dice-well filling behavior are almost agreed with the experimental ones. For the optimization of injection conditions the numerical simulation using FAN method is found to be useful only for the slurry showing the dice-well filling behavior.View full abstractDownload PDF (1067K) -
Yuji Muramatsu, Kazuhiro Honma, Akemitsu Miyazaki, Kunio Funami1996 Volume 60 Issue 11 Pages 1116-1124
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSintered TiAl alloys containing niobium of 1 to 5 at% were prepared by conventional sintering. Some of the sintered alloys were further densified by HIPing. Sintered and HIPed alloys were subjected to oxidation tests which were conducted in an N2-20 vol%O2 atmosphere at 1220 K. The oxidation behaviors of sintered and HIPed alloys were compared. The effect of niobium addition on oxidation resistance was examined. The scale structure and the mechanism of oxidation resistance were also examined.
The oxidation behaviors of these alloys differed from each other. The sintered alloys showed larger mass gains and earlier spalling in the oxidation stage. The niobium addition made it possible to reduce mass gain and to delay spalling. The HIPed alloys containing 4 and 5 at%Nb showed excellent oxidation resistance over an oxidation time of 1800 ks. EPMA analyses clarified that the scale formed on the sintered alloy of 5 at%Nb consisted of five or six layers in the following arrangement from outside,
TiO2/Al2O3(continuous)/TiO2+Al2O3(reticular)/TiN+Ti2AlN/Nb-rich+Al2O3(acicular)+Ti3Al/Ti3Al.
\ oindentThe scales of the HIPed alloys, without niobium and with 5 at%Nb, were found to have similar arrangements. In these alloys, although the TiN+Ti2AlN layer could not be detected by EPMA analyses, those nitrides were confirmed by X-ray analysis. Investigations on the mechanism of oxidation resistance suggested that the difference of oxidation behavior between sintered and HIPed alloys was caused by residual pores and structural differences of their scales, and that the improvement of oxidation resistance with niobium addition was due to the suppression of TiO2 growth and the promotion of dense and continuous Al2O3 formation.View full abstractDownload PDF (1728K) -
Katuo Saitou1996 Volume 60 Issue 11 Pages 1125-1129
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe arc current and voltage were taken as influence factors on the generation rate of ultrafine particles using an Ar-H2 arc plasma method and the effect of these factors on the ultrafine particle generation rate was studied.
Two types of the electrode tip shape, that is, the vertex angle of 90° and hemisphere, were used to investigate its shape effect on the generation rate.
Experiments were mainly carried out under Ar-50%H2 mixed gas at atmospheric pressure, the arc generation condition of 25-40 V and 90-220 A.
The generation rate of ultrafine particle under the condition of constant arc voltage gives the maximum value with respect to the arc current. The arc current which provides the maximum generation rate has the tendency that does not depend on the arc voltage when the electrode of acute shape is used.
The arc current dependence of the generation rate under constant arc voltage, three kinds of the voltage dependence were observed; the generation rate decreases monotonously, increases monotonously and have the minimum value with increasing arc voltage.
The arc current and voltage dependence of the generation rate is discussed from the view point of the magnitude of velocity of the plasma jet which generates from both the electrode and the anode heating by electrons.View full abstractDownload PDF (450K) -
Jianguo Hu, Keisuke Ikeda, Tadasu Murakami1996 Volume 60 Issue 11 Pages 1130-1135
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSingle roller driving cold-rolling (SRCR) was tried to develop the shear texture component {111}⟨110⟩ in pure aluminium, and the effect of the process on the texture development, r value and deep drawability was studied. The SRCR process, on the one hand, promotes the shear texture component {111}⟨110⟩ to some extent, and on the other hand, reduces the development of the pure metal type texture. The higher the reduction in thickness is, the more remarkable the effect of the SRCR process on the textural changes is. The shear texture component {111}⟨110⟩ almost disappears by subsequent annealing, suggesting that it may be unstable in the recrystallization process. Since the development of rolling texture in the SRCR processed sheets is weak, the recrystallization texture is considerably randomized, leading to \barr=0.8∼0.85 and Δr\fallingdotseq0. As a result, the SRCR processed sheet presents a large increase in the limit drawing ratio and very low earing height, in comparison with the conventionally cold-rolled sheet. It is suggested that perfect or inplane isotropy should be realized to improve deep drawability of aluminium and its alloy sheets, if the preferential development of the {111} texture component were unexpected.View full abstractDownload PDF (828K) -
Takuji Hara, Takuji Okiyama, Toshihiko Takemoto1996 Volume 60 Issue 11 Pages 1136-1142
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt is generally understood that the soft magnetic properties of Permalloy, especially permeability, decrease with decreasing Ni content. Many investigations have been carried out to improve the soft magnetic properties of Permalloy containing less than 50 mass%Ni. For example, the effects of addition of various elements on the soft magnetic properties have been reported. Main purpose of the present paper is to study the mechanism on improvement of soft magnetic properties of Fe-(34∼46)mass%Ni alloys by the addition of Cr. The results obtained are summarized as follows: μi and μL are improved by increasing Cr content. Especially, the effect of Cr addition is remarkable for Ni content between 35 and 38 mass%. The improvement of soft magnetic properties by the addition of Cr is contributed to the decrease in K1 and λ with increasing Cr content. Moreover, it is considered that the remarkable improvement of μi and μL by the addition of Cr more than 8 mass% for Ni content between 35 and 38 mass% is due to Hopkinson effect, because Tc of the alloys are just above room temperature.View full abstractDownload PDF (571K)
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