All issues
Volume 80, Issue 6
Displaying 1-9 of 9 articles from this issue
- |<
- <
- 1
- >
- >|
Review
-
Ryohei Yagi, Toru H. Okabe2016 Volume 80 Issue 6 Pages 341-349
Published: 2016
Released on J-STAGE: May 25, 2016
JOURNAL FREE ACCESSRhenium (Re) is used as additives in several alloys such as nickel-based superalloys for jet engine turbine blades, platinum catalysts for oil refining, and thermocouples used at ultra-high temperature, in order to improve strength and stability at high temperature. The demand of Re has been increasing with the increase in demand of the superalloys. In this article, current status such as demand and distribution of Re are reviewed, and smelting technologies for recovering Re from various ores are introduced.
View full abstractDownload PDF (4147K)
Regular Article
-
Shigeru Saito, Toshiyuki Takashima, Katsumi Miyama, Toshio Narita2016 Volume 80 Issue 6 Pages 350-354
Published: 2016
Released on J-STAGE: May 25, 2016
Advance online publication: April 15, 2016JOURNAL FREE ACCESSFormation of diffusion-barrier coating system with two-layered structure has been developed. The system comprises an inner χ-phase of the Re-Cr-Nb system as a diffusion-barrier layer and an outer Al-reservoir layer. In this study, Re film was formed on Nb substrate via electroplating and the film changed into χ-Re3Nb phase by preliminary heat treatment at 1500℃ for 1 h. Cr-pack cementation was conducted under vacuum of 10−5 Pa at 1300℃ and 1400℃ for 6 min and 1 h, respectively, using an Al2O3 crucible in which the specimens were buried in a powder mixture of pure Cr and Al2O3. The packed specimens were examined using an electron probe microanalyzer to determine the concentration profile of each element. The layer structure of the film on the Nb substrate after the Cr-pack cementation was discussed on the basis of composition paths plotted in the Re-Cr-Nb phase diagram.
In the case of the specimen induced by Cr-pack cementation at 1300℃ for 6 min, the alloy layers in the Re-Cr-Nb system consists of the γ, Re-rich, χ and α phases. In the case of the specimen induced by Cr-pack cementation at 1300℃ for 1 h and 1400℃ for 6 min, the alloy layers in the Re-Cr-Nb system consisted of the γ, χ and α phases. By contrast, in the specimen induced by Cr-pack cementation at 1400℃ for 1 h, the alloy layers in the Re-Cr-Nb system consists of the γ, Nb(Cr, Re)2 and α phases.
View full abstractDownload PDF (2423K) -
Keisuke Ueda, Chisato Kubo, Masae Kanda, Yoshitake Nishi2016 Volume 80 Issue 6 Pages 355-359
Published: 2016
Released on J-STAGE: May 25, 2016
JOURNAL FREE ACCESS2-layer laminated sheets (PP/PA6) with polypropylene (PP) and nylon 6(PA6) were prepared by applying low dose homogeneous low energy electron beam irradiation (HLEBI) prior to hot-press under 10 MPa, 403 K and 3 min. Although the adhesion of the PP/PA6 was often observed with a weak hot-press without HLEBI, the HLEBI (≦1.29 MGy) induced adhesion raised the bonding forces as evidenced by using the adhesive forces of peeling resistance (oFp). Based on the 3-parameter Weibull equation, the lowest oFp value at peeling probability (Pp) of zero (Fs) could be estimated. An increasing trend in Fs occurred by applying HLEBI up to 0.64 MGy reaching a maximum at 21.98 Nm−1, improving the safety level without radiation damage. When HLEBI cut the chemical bonds in PP polymer and generated not-terminated atoms having dangling bonds, they probably induced the chemical bonding. Thus, increasing adhesion force between the laminated sheets could be explained.
View full abstractDownload PDF (1352K) -
Masaya Okuhara, Ryo Nomura, Yoshitake Nishi2016 Volume 80 Issue 6 Pages 360-364
Published: 2016
Released on J-STAGE: May 25, 2016
Advance online publication: May 13, 2016JOURNAL FREE ACCESSHomogeneous low energy electron beam irradiation (HLEBI) to surface mostly improved the bending elastic modulus (b(dσ/dε)i) and tensile stiffnesst (t(dσ/dε)i) of composites sheets of glass fiber reinforced thermoplastic polypropylene (GFRTP). Although increasing dose of HLEBI decayed the ductility, optimal dosage of HLEBI from 0.22 to 0.86 MGy often improved the tensile strength (tσb) of the GFRTP with smaller variation in the data than untreated one. Based on the three parameter Weibull equation, the tσb at the lowest cummulative probability of fracture (Pf=zero) was estimated and defined as the lowest tensile strength (tσs). The highest tσs value estimated was 54 MPa for GFRTP irradiated at 0.65 MGy. Strengthening of both glass fiber and polypropylene, as well as their interfacial friction force mainly contributed to the results.
View full abstractDownload PDF (2154K) -
Ai Nozaki, Somchuen Kittima, Yasutomo Tanihara, Yasutaka Kuwahara, Tet ...2016 Volume 80 Issue 6 Pages 365-369
Published: 2016
Released on J-STAGE: May 25, 2016
Advance online publication: April 28, 2016JOURNAL FREE ACCESSThe catalytic performances of skeletal Cu prepared from Cu-Ti amorphous alloy heated at various temperatures were tested for the hydrogen generation from ammonia borane. The catalytic activity per surface area decreased with increasing heating temperatures of Cu-Ti amorphous alloy. The thermal treatment of Cu-Ti amorphous alloy leads to the high surface area of skeletal Cu. A skeletal Cu catalyst prepared from heated Cu-Ti amorphous alloy at 300℃ which is a moderate temperature somewhat lower than crystallization temperature, exhibited a higher catalytic activity in this reaction.
View full abstractDownload PDF (1746K) -
Takahiro Yabe, Masanori Enoki, Hiroshi Ohtani2016 Volume 80 Issue 6 Pages 370-378
Published: 2016
Released on J-STAGE: May 25, 2016
JOURNAL FREE ACCESSA thermodynamic analysis of the Al-Cu binary system has been performed to consider the metastable phase equilibria of the face-centered cubic (fcc) phase. The total energies of the ordered structures were obtained using first-principles calculations based on the fcc lattice. The cluster expansion method was applied to the results, and the free energies were calculated for the solid solution at finite temperatures. The results were analyzed together with some experimental data, and the equilibrium phase diagram of the Al-Cu binary system was calculated based on the CALPHAD (Calculation of Phase Diagrams) method. The results suggested a metastable two-phase separation of the fcc phase in the Al-rich region. The coherent spinodal line was calculated according to Cahn's treatment and revealed that the critical temperature decreased by about 100 K because of the coherency of the separated phases in the fcc matrix. In consideration of both Cahn's treatment and the effect of vacancies, it was suggested that the initial formation step of the Guinier-Preston zone might be relevant to the metastable coherent spinodal decomposition in the fcc solid solution.
View full abstractDownload PDF (2530K) -
Mie Ota, Kiichi Sawai, Daiki Nanya, Kei Ameyama2016 Volume 80 Issue 6 Pages 379-385
Published: 2016
Released on J-STAGE: May 25, 2016
JOURNAL FREE ACCESSThis investigation clarified the microstructural evolution in a two-phase stainless steel (329J1 grade), prepared by a mechanical milling (MM) and spark plasma sintering (SPS). The as-received stainless steel powder was produced by a plasma rotating electrode process and the microstructure of that was fully ferritic structure. After the MM, the single α phase coarse grain was changed to a bimodal α grain structure, formed nanocrystalline subsurface region and un-formed coarse grain inner region. SPS transformed from the powder with the bimodal α grain structure into “harmonic structure” of sintered compact. Namely, the fine-grain areas three dimensionally interconnect (“Shell” network) and the coarse-grain area periodically disperse (“Core”). The sintered (α+γ) two phase stainless steel exhibited a complex shell structure consisting of mid-shell and outer-shell regions. The α phase in the mid-shell is high angle boundaries and, that in the outer-shell is low angle boundaries. As the considered mechanism for such a complex microstructural evolution, the mid-shell is formed by grain growth of the α nano grains, followed by γ precipitation. On the other hand, the outer-shell is formed by the recovery of deformed α phase, and γ phase precipitates at the α subgrain boundaries. Consequently, the (α+γ) two phase stainless steel shows regularly aligned nano-duplex, micro-duplex and duplex structures, because of the competing procedure of recovery and recrystallization of α phase and γ precipitation.
View full abstractDownload PDF (4790K)
Rapid Publication
-
Yoshihiko Hangai, Yukiko Nakano, Takao Utsunomiya, Osamu Kuwazuru, Soi ...2016 Volume 80 Issue 6 Pages 386-389
Published: 2016
Released on J-STAGE: May 25, 2016
Advance online publication: April 15, 2016JOURNAL FREE ACCESSThin aluminum (Al) pipes filled with Al foam were fabricated by friction welding. In this study, thin Al pipes were formed from thin Al plates and were welded during the coating of a precursor by friction welding. It was shown that seamless Al foam-filled pipes with a uniform wall thickness can be realized. Compression tests on the Al foam-filled pipes revealed that the welding of the pipes had no effect on the generation of cracks in the pipes and their compression properties.
View full abstractDownload PDF (1456K) -
Yoshihiko Hangai, Ayano Ishihara, Takao Utsunomiya, Osamu Kuwazuru, No ...2016 Volume 80 Issue 6 Pages 390-393
Published: 2016
Released on J-STAGE: May 25, 2016
Advance online publication: May 13, 2016JOURNAL FREE ACCESSTwo layers porous aluminum (Al), consisting of a high porosity layer and low porosity layer in a single porous Al, was fabricated by a friction powder sintering process based on the sintering and dissolution process by varying NaCl volume fraction φ. In X-ray computed tomography (CT) images, two layers with φ=80% (high porosity) and φ=60% (low porosity) were clearly observed in the single porous Al. In compression tests of the fabricated two layers porous Al, the deformation started from the φ=80% layer then spread to the φ=60% layer. The stress-strain curves obtained in the compression tests revealed that the stress of the plateau region was lower during the deformation of the φ=80% layer than during the deformation of the φ=60% layer. The stresses in the plateau region during such deformations were almost the same as those of the uniform φ=80% and φ=60% porous Al. Consequently, it was shown that the two layers porous Al with varying porosity exhibited high and low plateau stresses with almost the same plateau stresses as uniform porous Al.
View full abstractDownload PDF (1193K)
- |<
- <
- 1
- >
- >|