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Volume 73, Issue 6
Displaying 1-12 of 12 articles from this issue
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Ichinori Shigematsu, Yong-Jai Kwon, Naobumi Saito2009 Volume 73 Issue 6 Pages 407-413
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSIn this study, tailor-welded blanks (TWBs) composed of A5052P-O aluminum and AZ31B-O magnesium alloys were produced by the friction stir welding process. Sound surfaces without large defects were successfully obtained at the tool rotation speeds ranging from 1000 to 1400 rpm under constant tool traverse speed of 300 mm/min, and the surface roughness was decreased in the friction-stir-welded zone (SZ) with the increase in the tool rotation speed. Also for 100, 300 and 500 mm/min, the sound surfaces without large defects were obtained under the constant tool rotation speed of 1400 rpm. The increase of the tool traverse speed led to the decrease in the surface roughness of the SZ. In the SZ, the bonded interface was clearly evident with plastic flow pattern between the aluminum and magnesium alloys, although an onion ring pattern was not formed. During tensile testing, the TWBs were fractured in the SZ at the early stage of the plastic deformation, i.e. strain hardening region, without remarkable area reduction near the fracture region. The TWBs exhibited the similar average tensile strength, showing that there were not noteworthy changes in the tensile strength as a function of the tool rotation speed. The average tensile strength, however, was slightly decreased with the increase in the tool traverse speed. It is noticeable that, in all cases, the joint efficiency of the TWBs exceeded 62%, and the maximum average tensile strength of about 143 MPa was obtained at 1400 rpm under the tool traverse speed of 100 mm/min, which was nearly equivalent to the joint efficiency of about 72%. The average total elongation of the TWBs was about 2% or less considerably lower than those of the base metals, without significant changes as functions of the tool traverse speed and the tool traverse speed.
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Hidekazu Sueyoshi, Ryosuke Ishii, Hisayoshi Fukudome, Shinji Mizokuchi ...2009 Volume 73 Issue 6 Pages 414-420
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSIn order to develop an advanced soldering material, the Cu/Fe alloys were produced by using powder metallurgy and the soldering properties were examined. Thermal conductivity of Cu/Fe alloy decreased with the increase in the volume fraction of pores, while it increased with the increase in the volume fraction of Cu particles. Wettability of Cu/Fe alloy was better than that of conventional Fe plating, resulting in a reduction in soldering temperature. Comparing the consumption amounts under the same wettability, the amount of Cu/Fe alloy consumed was smaller than that of Fe plating consumed.
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Motoki Hishida, Masashi Fujita, Kazuhiko Sakaki2009 Volume 73 Issue 6 Pages 421-428
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSIt is known that quasicrystalline phases have high Vickers hardness and high thermal stability. Heat-resistant aluminum alloys, which contain dispersed nanoscale quasicrystalline particles and have very high tensile strength at highly elevated temperatures (473 to 673 K), were developed in 2006. We aimed to partially strengthen components using the developed material as a coating material. However, the general spraying technology, if used, would expose this coating material to high temperatures, causing the quasi-crystalline phase to decompose into an intermetallic compound phase.
In this study, aluminum alloy coatings containing dispersed nanoscale quasicrystalline particles have been produced using the cold spray method, which can be performed at comparatively lower temperatures.
Rapidly solidified powder was produced by the atomization method, which consists of a combined high-pressure gas atomization and water atomization process. The cold spray process was carried out on nitrogen or helium gas at 3 MPa and 673 K. As a result of X-ray analysis and DSC measurement, it was ascertained that the dispersed quasicrystalline structure is maintained even after the cold spray coating process. Also from TEM observation, the dispersed quasicrystalline structure was maintained within the coating.
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Akira Tateno, Akihiro Sato, Yasuo Matsunaga2009 Volume 73 Issue 6 Pages 429-433
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSIn this study, a thermal barrier coating (TBC) was applied to a 4th generation Ni-based single crystal superalloy TMS-138 and its spallation life in thermal cycling condition at 1135°C was compared with the case of CMSX-4 substrate. Pt-modified nickel aluminide coating was applied as bond coat and yttria-stabilized zirconia prepared by electron beam physical vapor deposition was applied as topcoat.
The spallation lives of TBCs on TMS-138 substrate were 700-1000cycles and longer than that of TBCs on CMSX-4 substrate. In TBCs on TMS-138 substrate, the ratcheting at bondcoat surface hasn't grown up with increased thermal cycle and it was different from the case of TBCs on CMSX-4 substrate. It was suggested that creep strength of bondcoat was increased and put retains the rumpling in Ru-bearing TMS-138 alloy.
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Syugo Miyake, Aya Miyake, Ken-ichi Ikeda, Hiroyuki Takamatsu, Takashi ...2009 Volume 73 Issue 6 Pages 434-438
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSA novel thermal conductivity measurement technique combining a periodically modulated thermoreflectance method with numerical simulation has been developed to precisely estimate the thermal conductivity of sub-micrometer thickness metal films. Numerical simulation about the surface temperature response was carried out assuming that the sample surface is irradiated by variable heating area in micrometer order using an amplitude modulated laser beam. Analyzed results show that the phase lag of the reflectance signal depends on not only the thermal effusivity but also on the thermal diffusivity of the film in local heating. Hence, the thermal conductivity determined by the thermal effusivity and the thermal diffusivity can be evaluated by the dependence of the phase lags on the heating area. This technique was applied for Cu(1-X)PtX (0≦X≦1.63 at%) films with 300 nm thickness deposited on glass substrates. The evaluated thermal conductivity varies from 340 W/(mK) to 97 W/(mK) with increasing Pt concentration. We found that the thermal conductivity of the Cu thin film becomes less than 90% of that of the bulk value (~400 W/(mK)). Moreover, the evaluated thermal conductivity was confirmed to correspond well to the electric conductivity with the Wiedemann-Franz law.
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Makiko Yonehara, Shinji Kumai, Hiroaki Isono, Koichiro Kihara, Toshio ...2009 Volume 73 Issue 6 Pages 439-445
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSTexture is one of the important factors to characterize appearance of products. However, its quantitative evaluation is difficult and the proper evaluation method has not been developed yet. In order to solve this problem, in the present study, we proposed several parameters applicable for quantitative texture evaluation. Copper alloys, representative chromatic colored metals, were used as test materials. The surface color was controlled by using Cu-Zn and Cu-Sn alloys with different compositions. A series of alloy plates with various surface roughness conditions were prepared by shot-blasting. Effects of surface roughness on glossiness and surface color were investigated for shot-blasted surfaces. With decreasing surface roughness, glossiness increased, while, lightness of surface color decreased. In contrast to that, hue of surface color is a characteristic color parameter for each material and never change with surface roughness. The present experimental results showed that the texture can be evaluated quantitatively by using three combined parameters: surface roughness, glossiness and surface color.
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Yuji Nishihara, Hiroshi Ohtani, Mitsuhiro Hasebe2009 Volume 73 Issue 6 Pages 446-452
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSA thermodynamic analysis of the Pu-U-B ternary system has been carried out using the CALPHAD method. The formation energies of the boride phases MB2, MB4, MB12 of this system obtained from first-principles calculation were utilized to compensate for the lack of experimental information on the phase boundaries and thermodynamic properties of this system. The optimized thermodynamic parameters reproduced the characteristic features of binary phase diagrams quite well. The liquidus surface and isothermal sections were calculated. According to the calculated results, the liquidus temperature was raised with increasing B content.
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Takeshi Hamada, Hidetaka Kanahashi, Naoyuki Kanetake2009 Volume 73 Issue 6 Pages 453-461
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSClosed cell porous Al has extremely low mass and provides high energy absorption performance. However, because of its low tensile strength, it has been expected to be used as porous Al filled members with a dense surface material, as well as to clarify its axial crushing performance.
In this study, the effect of the axial crushing performance by porous Al filled members, the impact crushing test using several hollow forms and porous Al filling in different ways were examined, and FEM analysis was carried out.
As a result, the energy absorption was increased about 1.6 times by press filling, and about 2.0 times by glue-press filling porous Al from the sum of individual one of hollow forms and porous Al; thus, the porous Al filled members provided the interaction effect. Based on the test result and the elastic-plastic FEM analysis in which the crushing behavior matched the test result, it was proved that the energy absorption was increased since the buckling transformation to inside forms was restrained. Moreover, porous Al penetrates inside transformation by glue-press filling and press filling porous Al, and accordingly the deformation resistance in the compression direction increased. This increase of the deformation resistance in the compression direction causes forms axisymmetric collapse mode, and the interaction effect of porous Al filled members can be expressed in as much that the form thickness apparently increases due to the effect of the mass of filling material. The estimate equation of the mean crushing stress as an index of the energy absorption well-matched the test result. Therefore, it was proved that the mass of filling material contributes as an additional thickness of forms. In addition, the interaction effect is decided by a filling method.
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Nahoko Sugioka, Masahiro Kitada2009 Volume 73 Issue 6 Pages 462-468
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSThe microstructures and distribution of an orange dyestuff compound in the cotton fiber used for touzan fabric imported in the late Edo period have been investigated. The dyed fibers are taken off from the old fabric. The color of the fabric is measured with a spectrophotometer. To observe the distribution of nanometer-sized compound grains in the fiber, the cross section of the fiber is flattened by ion milling after mechanical polishing. The microstructures are observed by SEM and TEM. The composition and crystal structure are analyzed by EDX and XRD. The absorption edges at 590 nm (2.1 eV) and 720 nm (1.7 eV) are observed in the reflectance spectrum for an orange thread. The orange color is determined by the edge at 590 nm. The spectral luminous efficacy spectrum shows a peak at 574 nm. The dyestuff compound, Pb2CrO5, is detected by EDX and XRD. Although the film like compound covers the cotton fiber surface, the fine compound of 100~500 nm precipitates in the fiber. Most of these precipitates align along the fiber forming concentric circles; however, some precipitates distribute randomly. The preferential precipitation is observed at a crack in the fiber and a precipitation-free zone is also observed. The compound, Pb2CrO5, precipitates preferentially at a defect, which is possibly an amorphous structure, in the fiber. It is considered that the distribution of the precipitates indicates the defect structure of the fiber.
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Michinari Yuyama, Tadaharu Yokokawa, Yutaka Koizumi, Toshiharu Kobayas ...2009 Volume 73 Issue 6 Pages 469-474
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSWe constructed a database for Ni-base Superalloys development. The database includes many data related to Superalloy development in areas of chemical composition in alloy design, casting and heat treatment in processing, and results of creep tests, thermal fatigue tests, oxidation tests, and so on. This distributed-type database includes small database systems for each category of data, such that it is possible to retrieve required data from an individual category. The system, which performs all data retrieval, is arranged upstream of these small databases and refers to the data according to its relation from all small databases. While enhancing data security, the system enables effective and reliable retrieval. Using the database, evaluation and analysis can be performed using huge volumes of data related to Superalloy development.
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Akira Matsuzaki, Masaaki Yamashita, Nobuyoshi Hara2009 Volume 73 Issue 6 Pages 475-483
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSIt is known that chromate pretreatment films with dry type silica have a good adhesion to organic films such as paint and laminate films on a zinc coated steel sheet. The adhesive mechanism has been investigated from the standpoint of surface polarity for a long time, but has not been perfectly explicable. In this work, a correlation between the composition of chromate pretreatment films with dry type silica and the adhesion to a laminate film on a zinc coated steel sheet was examined in comparison with the chromate pretreatment films with wet type silica and without silica. Furthermore the adhesive mechanism has been investigated by the analysis of the pretreatment films using SEM, AFM, BET method, TEM and EDX.
The results are summarized as follows:
Not only the type and the particle size of silica, but also the silica/chromate ratio and the coexistence of chromate affected the adhesion of laminate films. The highest adhesive strength was obtained for the pretreatment films formed in a pretreatment solution with SiO2/Cr ratio of 4.0 and dry type silica with a diameter of 7 nm. The good adhesion of chromate pretreatment films with dry type silica is due to an anchor effect by sub-micron surface roughness and an increased in number of interface bonding sites by a nano-porous structure. The formation of an insoluble Cr(III) compound layer plays an important role in binding silica particles to the zinc coating surface.
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Letters to the Editor
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Yoshihiko Hangai, Takao Utsunomiya2009 Volume 73 Issue 6 Pages 484-486
Published: 2009
Released on J-STAGE: June 01, 2009
JOURNAL FREE ACCESSPorous aluminum is a multifunctional material that is both lightweight and has high energy absorption. We attempted to fabricate closed-cell porous aluminum using aluminum alloy die castings, which contain a large amount of gas. This proposed die castings route has great potential for realizing high productivity, low energy consumption and low-cost manufacturing. The aim of this study is to investigate the validity of the die castings route for fabricating closed-cell porous aluminum. Also, the effect of using the friction stir processing technique to uniformly disperse the oxide, inclusions and gas in the die castings on the morphology of the pores and porosity was investigated. It was shown that porous aluminum with high sphericity and a porosity of more than 30% was realized by using the friction stir processing technique and optimizing the holding time.
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