Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 62 , Issue 5
Showing 1-12 articles out of 12 articles from the selected issue
  • Yuji Kurata, Hirokazu Utsumi
    1998 Volume 62 Issue 5 Pages 413-419
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Change in creep curve shapes of a Ni-22Cr-18Fe-9Mo alloy developed for an intermediate heat exchanger of high temperature gas-cooled reactors has been investigated with the following results: (1) Creep curves at 800°C for this alloy, in the solution-treated and aged conditions, are tertiary creep dominated ones where most of the life is an accelerating creep stage although a primary creep stage is slightly recognized in some cases. (2) Creep curves at 1000°C for this alloy in a solution treated condition are irregular ones which have a region with a low creep rate preceding the steady-state creep rate and accelerating creep rate. This low creep rate stage diminishes after aging at 1000°C. Creep curves at 1000°C for the aged alloy are normal type ones. (3) Creep rates at 800 and 1000°C increase after aging at 1000°C. This effect is small under low stresses at 1000°C. Rupture strain of the aged alloy increases because carbides formed on grain boundaries by aging suppress the formation and growth of voids and cracks.
    Download PDF (1189K)
  • Yuji Kurata, Hirokazu Utsumi
    1998 Volume 62 Issue 5 Pages 420-426
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Applicability of the θ projection method has been examined for constant-load creep test results at 800 and 1000°C on Ni-22Cr-18Fe-9Mo alloy in the solution-treated and aged conditions. The results obtained are as follows: (1) Normal type creep curves obtained at 1000°C for aged Ni-22Cr-18Fe-9Mo alloy are fitted using the θ projection method with four θ parameters. Stress dependence of θ parameters can be expressed in terms of simple equations. (2) The θ projection method with four θ parameters cannot be applied to the remaining creep curves where most of the life is occupied by a tertiary creep stage. Therefore, the θ projection method consisting of only the tertiary creep component with two θ parameters was applied. The creep curves can be fitted using this method. (3) If the θ projection method with four θ or two θ parameters is applied to creep curves in accordance with creep curve shapes, creep rupture time can be predicted in terms of formulation of stress and/or temperature dependence of θ parameters.
    Download PDF (553K)
  • Makoto Ishikawa, Nobuyuki Koura, Hiroyuki Miyazaki, Takayoshi Iseki, T ...
    1998 Volume 62 Issue 5 Pages 427-435
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    A graphite-addition pelletizing technique proposed by the authors has been successfully applied to the determination of nitrogen in the ppm range in powdered vanadium. Complete extraction of total nitrogen from pellets of 5 mm diameter weighing from 0.1 to 0.5 g with graphite addition of more than atomic ratio of 1 or above requires an impulse furnace heating at about 3000°C within the 100-s gas collection. The results obtained by the proposed method were in agreement with those obtained by the Kjeldahl method for higher content sample, and showed slightly higher results for the samples containing 0.02 to 0.04 mass% nitrogen. From the results of the investigations of the effect of an impulse heating power on the extractability of nitrogen, the crucible aspects after use, and X-ray identification of the products formed in the crucible, nitrogen from the pellet with a 1:1 atomic ratio of graphite was released at about 2900°C in a solid state, accompanying complete formation of a VC phase. Residual nitrogen in the sample can be extracted at about 3000°C in a melting or half-melting state of the pellet. From these results, the separation of peaks can be observed by a two-step technique; the first step at about 2900°C for 50 s and the second step at about 3000°C for next 60 s power supply. The extraction of nitrogen from a VC pellet was also reported.
    Download PDF (996K)
  • Yoshinori Sakamoto, Takehiko Mae, Sumiko Sanuki, Hisakimi Notoya, Koic ...
    1998 Volume 62 Issue 5 Pages 436-443
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    The changes in mechanical properties and corrosion resistance of Al-Mg alloys with the addition 10 mass%Ni by the electron beam welding process were investigated by the tensile test and the immersed corrosion test of the specimens with or without improved treatment in 1×10−1 kmol·m−3 HClO4 solution at 303 K.
    The X-ray diffraction or EDAX analysis of the precipitates and the observations of scanning electron micrographs of the specimens and the surfaces of the corroded specimens were also performed.
    The main results obtained are summarized as follows:
    (1) The needle structure of Al3Ni(β) intermetallic compound and Al(α)+Al3Ni(β) eutectic structure was precipitated by the improved treatment of Al-Mg alloys. Furthermore, the small size of teritectic structure of Al3Ni(β) and Al3Ni2(γ) intermetallic compounds was also detected. (2) The mechanical properties such as 0.2% proof stress and Vickers hardness of Al-Mg alloys were increased by the improved treatment. On the contrary, the values of U.T.S. and elongation of the improved specimens were reduced in comparison with the untreated specimens regardless of the Al-Mg alloys. (3) The corrosion resistance of the improved specimens decreased slightly compared with that of the untreated specimens. The deterioration of the corrosion resistance was caused by an electrochemical interaction of galvanic coupling produced between the grains of Al(α) phase in the eutectic structure and the Al3Ni(β) intermetallic compound.
    Download PDF (1297K)
  • Hirohisa Masuda, Hiroyuki Nishida, Kenji Morinaga
    1998 Volume 62 Issue 5 Pages 444-448
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Thermal expansion parameter, αp, which is based on the potential energy between cation-anion, has been proposed to estimate the thermal expansion coefficients of oxide glasses. αpi (i for the ith species) is defined as
    (This article is not displayable. Please see full text pdf.)
    \ oindentby charge Z, Born exponent n and the equilibrium interatomic distance req calculated from the ionic radius. In this study, αp of multicomponent oxide glasses were calculated on the assumption that the additivity of αp was hold for the glasses, and the applicability of αp for the glasses was investigated. As a result, it was revealed that many silicate glasses, including borosilicate and aluminosilicate glasses, could be divided by cation valence of network modifier oxide and an approximately linear relationship existed between the thermal expansion coefficient and αp in each division. It became possible to estimate the thermal expansion coefficient of silicate glasses accurately using the relations obtained in this study.
    Download PDF (391K)
  • Masahiro Fukumoto, Masakatsu Itoh, Yasunori Tanaka, Hisataka Yakabe, K ...
    1998 Volume 62 Issue 5 Pages 449-456
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Much attention has recently been paid to thermoelectric conversion material (TEC) as one of the candidate technologies for energy saving. In many configurations of TEC, thick coating may be advantageous in laminating or joining. Thermal spraying, by which the thick coatings of hard-forming materials can be easily made, is worthy of remark among several processings. However, a conventional method, a spraying of blended elemental metals powder followed by post-heat treatment, is hard to apply because a strict control of elemental composition by delicate heat treatment is required to get the high performance TEC.
    In this study, homogeneously mixed metal/metal composite powders, which were made by mechanical alloying (MA) process, were applied to plasma spraying in order to obtain the intermetallic TEC coatings, and the processing for getting the TEC coating was fundamentally investigated. The great merit of MA process is the possibility of controlling the additional dopant fraction and creating the fine and homogeneous structured composite powders.
    Consequently, optimum conditions of mechanical alloying, plasma spraying and post heat treatment to get the appropriate thermoelectric phases for Fe-Si systems were empirically decided. Under the optimum conditions, the thermoelectric properties in the systems were estimated as a function of dopant molar fraction.
    Download PDF (1356K)
  • Tetsuji Saito, Masakazu Fujita, Kiyoto Fukuoka, Yasuhiko Syono
    1998 Volume 62 Issue 5 Pages 457-461
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    Nd-Fe-B amorphous powders with a typical composition and those with lower Nd content were prepared by rapid solidification processing. These amorphous powders were consolidated into bulk materials by dynamic compaction using the gun method. The resultant bulk materials retained the amorphous structure in both alloys. The Nd-Fe-B bulk materials with a typical composition were successfully deformed by die upsetting, but the bulk materials of Nd-Fe-B alloys with lower Nd content were not deformed by die upsetting. The metastable Fe3B phase and α-Fe phase together with Nd2Fe14B phase that had crystalized during the die upsetting prohibited the bulk materials from the deformation.
    Download PDF (998K)
  • Toshinori Fujii, Masaya Kuzutani, Nobuhiro Nakabo, Kei Ameyama
    1998 Volume 62 Issue 5 Pages 462-468
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    A Ti-48 mol%Al intermetallic compound was produced by a mechanical milling (MM) process using titanium hydride and aluminum powders. Microstructure change during heating of the Ti-48 mol%Al MM powder particles as well as microstructure of the MM powder particles and the vacuum hot pressed compact were investigated. Almost 95% of the MM powder was yielded by this process. Approximately 20% of the titanium hydride powder dehydrogenated and changed to an α-Ti phase during the milling process, followed by the dispersion of an ultra-fine mixture of the titanium hydride and α-Ti particles within an aluminum powder particles. Mean particle sizes of the titanium hydride and α-Ti particles in the MM powder particles were approximately 6 nm in diameter. Differential scanning calorimeter analysis and X-ray diffraction analysis revealed that dehydrogenation took place between 600 K and 900 K, and a Al3Ti phase formed by the reaction of the α-Ti and aluminum phases. The vacuum hot press compact sintered at 1173 K showed a fine equiaxed (TiAl+Ti3Al) microduplex structure with a grain size of approximately 750 nm.
    Download PDF (1375K)
  • Yukio Inokuti
    1998 Volume 62 Issue 5 Pages 469-475
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    In order to clarify the difference in the textures of Ti films made on (011)[100] single crystal of silicon steel, Ti coatings by the hollow cathode discharge(HCD) and electron beam(EB)+radio frequency(RF) methods were made on the surfaces of the polished silicon steel samples. Pole figures of the textures of the Ti and silicon steel samples were measured simultaneously using a solid-state detector(SSD) auto pole figure apparatus.
    A {1010}Ti pole figure of the Ti films done by the HCD method showed a dominant (10\bar10) [1\bar210] oriented texture.
    In contrast, a {1010}Ti pole figure of the Ti films done by the EB+RF method showed a weaker texture than that by the HCD.
    It is considered that, due to the higher ionization by the HCD method than that by EB+RF, it was possible for the Ti films to form the dominant (10\bar10) [1\bar210] texture. Also, it should be noticed that the dominant (10\bar10) [1\bar210] texture of the Ti films was formed peferentially on the surface of the (011)[100] single crystal of silicon steel with a 3.5% between [1\bar210]Ti and [100]Si-steel atomic distances.
    Download PDF (518K)
  • Hiroya Sawairi, Masahiro Fujikura, Takashi Sato
    1998 Volume 62 Issue 5 Pages 476-480
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    The effects of quench rate during casting and alloy composition on surface crystallization and the magnetic properties are investigated for amorphous Fe-Si-B alloys containing Al and Ti as impurities. In the presence of these impurities, the amorphous alloys tend to be surface-crystallized. Furthermore, the surface crystallization is more prominent at low quench rates. Also, the alloys of high Fe content (low glass forming ability) are found to have the same tendency. TEM observation of the free side of the ribbons reveals that there is a big difference between Al and Ti in crystallization behavior. These phenomena are supposed to originate from the difference in lattice coherency between α-Fe and the precipitates in which two impurities act as nuclei of crystallization.
    Download PDF (816K)
  • Masami Taguchi, Tsukasa Baba, Kazunori Kanda
    1998 Volume 62 Issue 5 Pages 481-487
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    The thin film PbO2/PbO/Pb solid cells were produced by reactive sputtering and vacuum evaporation on glass substrates, and the discharge properties were investigated. A PbO2 layer was obtained by sputtering of the Pb target in oxygen plasma. PbO, which is an oxygen ion conductor, was deposited from β-PbO powder in a vacuum. The open-circuit voltage of the PbO2/PbO/Pb cell was in good agreement with the theoretical value based on the thermodynamic data, and the partial transformation of β-PbO to α-PbO in the electrolyte did not show any marked change in voltage. The close-circuit voltage, which could be measured by connecting with a 100 kΩ resistor, was deteriorated by doping of the Bi3+ ion to the electrolyte, PbO. On the other hand, the doping of the K+ ion inhibited the decrease in discharge voltage. Moreover, the charge-discharge cycling test revealed that the PbO2/PbO/Pb cell could be charged to behave as a storage battery and that the connection of the cells in series and in parallel supplied a higher electromotive force and a larger capacity.
    Download PDF (684K)
  • Hiroyuki Toda, Toshiro Kobayashi, Yukiya Tanaka, Takashi Gouda
    1998 Volume 62 Issue 5 Pages 488-496
    Published: 1998
    Released: April 24, 2008
    JOURNALS FREE ACCESS
    The present authors have developed distinct two-phase composites comprising a spherically-clustered phase on the basis of a numerical crack propagation simulation. The composites showed much higher strength as well as the predicted higher crack propagation resistance than the conventional composite with uniform reinforcement distribution. The present work aims to clarify the superior strengthening mechanisms for the composites with the segregated microstructure.
    Two-dimensional idealized microstructures in which one phase is continuous and the other isolated are modeled for the case where the clustered phase is continuous and for the opposite case. To predict the effect of the segregated microstructures on the strengthening ratio of composites in comparison to unreinforced materials, elastic-plastic finite element method is applied. As the degree of clustering increases, the strengthening ratio of composites increases within the context of this study. The strengthening ratio of composites with a continuous cluster is superior to that of an opposite case. This result could be attributed to the local relaxation of additional internal stresses in the clusters due to the predominant plastic deformation of a softer phase around the clusters when they are isolated. The regular array of clusters always enhances composite strengthening when each cluster contains a sufficient number of reinforcements and its spatial distribution in the clusters is uniform. Primary mechanism, by which additional strengthening arises due to the clustering, is attributed to the large difference in deformation resistance between the metal and the ceramic reinforcement in MMCs. The present composite models are considered to have a structure that the reinforcement clusters reinforce the softer phase. When the overall volume fraction of reinforcements is held constant, the existence of the optimum ratio of elastic moduli or secant moduli between two phases is predicted for the strengthening ratio of composites. Since the optimum ratio is much lower than that of the case of metal/ceramic, i.e., ordinary MMCs, the introduction of a dual phase structure in which both phases can deform elastic-plastically produces high strengthening ratio of composites.
    Download PDF (792K)
feedback
Top