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Volume 80, Issue 8
Displaying 1-7 of 7 articles from this issue
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Regular Article
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Bin Liu, Yasushi Sasajima, Akihiro Iwase2016 Volume 80 Issue 8 Pages 497-502
Published: 2016
Released on J-STAGE: July 25, 2016
Advance online publication: June 10, 2016
JOURNAL FREE ACCESSThe θ′ precipitation process of Al-Cu alloy was simulated with the coupling model of a phase field and a concentration field during isothermal annealing and under thermal irradiation. This model successfully described the θ′ precipitation process under isothermal annealing at 423 K and 473 K, including the growth rate of the θ′ precipitates. The model was used also to simulate the θ′ precipitation process under thermal irradiation at 473 K and it was found that the size and the distribution of the θ′ precipitates can be controlled locally by this process. The simulation results also indicated that the heat sink process around the irradiated area is important to achieve a precisely-controlled precipitated structure.
Fig. 6 Fullsize ImageMicrostructure evolution in Al-Cu alloy under 473 K thermal irradiation.View full abstractDownload PDF (2487K) -
Ryo Yamaguchi, Arata Yagi, Chisato Kubo, Masae Kanda, Yoshitake Nishi2016 Volume 80 Issue 8 Pages 503-507
Published: 2016
Released on J-STAGE: July 25, 2016
Advance online publication: June 03, 2016JOURNAL FREE ACCESSThe effects of homogeneous electron beam irradiation (EBI) at room temperature on the adhesive force of peeling at each peeling probability (Pp) of laminated sheets of bio-adaptable polydimethylsiloxane (PDMS) with great formability property and chemical resistance polymethyl methacrylate (PMMA) with sterilization were investigated without glue. EBI within the range of 0.22 to 0.30 MGy increased the adhesive force of peeling (°Fp) at higher cumulative probabilities from 0.77 to 0.94, substantially over the untreated. The largest °Fp values at optimal dose of 0.22 MGy were 116.0 Nm−1, which were more than 17 times larger than 6.7 Nm−1 of the untreated at high peeling force at the highest cumulative probability of 0.94. XPS (X-Ray Photoelectron Spectroscopy) observations of the peeled 0.22 MGy irradiated PMMA revealed generation of a SiC peak at 101.3 eV possibly explaining the increased adhesion. The residual PDMS deposition is apparently found to be retained on the PMMA by inter-matrix fracture of PDMS further into the thickness. This can be explained by the adhesion force between PMMA/PDMS being stronger than the cohesive force of PDMS polymer itself.
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Koji Kakehi, Rei Yokomori, Tomohiro Nishimaki2016 Volume 80 Issue 8 Pages 508-514
Published: 2016
Released on J-STAGE: July 25, 2016
Advance online publication: June 17, 2016JOURNAL FREE ACCESSAs the material of turbine discs for the civil airplane, PM (powder metallurgy) superalloys have been in practical use. This is because the advantages of PM superalloys are more pronounced in homogeneous structure, mechanical properties and yield rate than the disadvantage in the cost of the processing cost such as HIP (Hot Isostatic Pressing) by the advance in technology to produce alloy powders. However, PPB (Prior Particle Boundary) is known to decrease the toughness and ductility of PM alloys. For these critical applications, the consolidated alloy powder particles are smashed up to break down carbide and oxide networks, known as prior particle boundaries (PPBs), and to refine the structure into a fine grain size by isothermal forging. High quality powder can be produced by Plasma Rotating Electrode Process (PREP). In this study, for getting the fine grain and high strength and elongation, the PREP powder was HIPed at a δ-subsolvus temperature because δ precipitate prevents grain growth. The relationship between the microstructure and mechanical properties was investigated using PREP powder and lower HIP temperature.
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Tetsu Suzuki, Daisuke Ando, Hidetoshi Somekawa, Yuji Sutou, Junichi Ko ...2016 Volume 80 Issue 8 Pages 515-520
Published: 2016
Released on J-STAGE: July 25, 2016
Advance online publication: July 01, 2016JOURNAL FREE ACCESSThis paper reports the microstructure observation and crystal orientation change during Erichsen test on Mg-Y extruded alloy sheets. The Erichsen value of Mg-Y alloy was 4.2 which was higher than 1.8 of AZ31 commercial alloy rolled sheet. The result shows Mg-Y alloy has high formability than AZ31 rolled sheet.
From the EBSD results of their crystal orientation change, tensile twin formed from early deformation stage and the area fraction of tensile twin increased with increasing the Erichsen value. In this time, crystal orientation changed to c axis parallel to nominal direction. During the Erichsen test, the randomly crystal orientation change to strong basal texture due to tensile twin. On the other hand, compression and their double twins formed on the strong basal textured grains from medium deformation stage. These compression twins easily formed the grains because of high Schmid factor for compression twin. The area fraction of these compression twins increased to 5% with increasing the Erichsen value. It was reported that double twins accompanied localized severe deformation and triggered premature failure in strong basal texture Mg alloy. Therefore, even in Mg-Y alloy with randomly crystal orientation, the crystal orientation change to strong basal texture due to tensile twin and it is presumed that these double twins also triggered premature failure.
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Taichi Onoe, Eiji Sekiya, Yoshio Sugita, Keisuke Tsukui, Naohiro Saruw ...2016 Volume 80 Issue 8 Pages 521-528
Published: 2016
Released on J-STAGE: July 25, 2016
Advance online publication: June 24, 2016JOURNAL FREE ACCESSBecause a stainless steel has an excellent corrosion resistance, it has been used in various fields such as daily necessities, automobile components, and chemical plants. However, it is well known that a stainless steel has a poor wear resistance resulted from its low hardness. Surface modification technique for improving the wear resistance is desired without deteriorating the excellent corrosion resistance. In the present study, nitriding treatment of a sus304 stainless steel was carried out using a newly developed plasma nitriding apparatus. X-ray diffraction analysis revealed that nitrides formed on the specimen surface were a S-phase and CrN. Nitriding-time progress brought about the thickness growth of nitrides. Simultaneously, lattice strain and amount of solid solution of nitrogen atom were increased significantly. The wear characteristics of nitrided sus304 had the thickness dependence of S-phase. In particular, the thickness increase of S-phase resulted in decrease of the wear volume. CrN showed inferior wear characteristics than S-phase due to brittle mechanical properties of its.
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Sojiro Uemura, Takateru Yamamuro, Joung Wook Kim, Yasuhiro Morizono, S ...2016 Volume 80 Issue 8 Pages 529-538
Published: 2016
Released on J-STAGE: July 25, 2016
Advance online publication: July 01, 2016
JOURNAL FREE ACCESSMo-Si-B-TiC alloys have been produced as candidates for a ultrahigh-temperature materials to replace Ni-base superalloys. We have quantitatively investigated the microstructure of a Mo-Si-B-TiC alloy composition. Mo-5Si-10B-10TiC (65Mo alloy) (at%) produced via arc-melting and tilt casting techniques. The starting material was composed of four constituent phases: Mo solid solution (Moss), Mo5SiB2, (Ti, Mo)Cx, (Mo, Ti)2C, and their eutectic (or peritecteutectic) phases. The compositions of these constituent phases were determined by EPMA. SEM-EBSD measurements revealed that T2 and (Ti, Mo)Cx phases have orientation relationships with Mo phase: {110}Mo//(001)T2, 〈111〉Mo//〈100〉T2 and {110}Mo//{111}(Ti, Mo)Cx, 〈111〉Mo//〈110〉(Ti, Mo)Cx. Furthermore, 3-dimensional SEM examination combined with the FIB serial sectioning technique demonstrated that the T2 phase had a thin plate shape of orientation (001) for the plate surfaces and {100} for side ones.
Fig. 10 Fullsize ImageThree-dimensional phase images reconstructed from serially-sectioned images: (a) (Ti, Mo)Cx and T2(Mo5SiB2), (b) (Ti, Mo)Cx, (c)T2.View full abstractDownload PDF (9165K) -
Yuki Sato, Satoshi Oue, Shinichi Heguri, Hiroaki Nakano2016 Volume 80 Issue 8 Pages 539-545
Published: 2016
Released on J-STAGE: July 25, 2016
Advance online publication: July 01, 2016JOURNAL FREE ACCESSTo investigate the effect of impurities in solution on the lightness, surface morphology and current efficiency of deposited Ni, Ni electrodeposition was performed at a current density of 300 A/m2 and 7.2×105 C•m−2 of charge, in an unagitated chloride solution containing Mn2+, Cr3+ and SO42− ions as impurity with pH 1 to 3, at 333 K. In solution containing 10 g•dm−3 of Mn2+, the current efficiency for Ni deposition decreased slightly, and crystal size of deposited Ni became small. The lightness of deposited Ni decreased when the concentration of Mn2+ exceeded 1 g•dm−3. When the Ni deposition was performed using soluble Ni anode to prevent the formation of MnO2 at anode, the lightness of Ni was higher than that using insoluble anode, which suggesting that MnO2 resulting from insoluble anode caused the decrease in lightness of Ni. In solution containing Cr3+, the current efficiency of Ni gradually decreased with increasing concentration of Cr3+, and significantly decreased above the Cr3+ concentration of 0.1 g•dm−3. The lightness of deposited Ni greatly decreased with increasing concentration of Cr3+ above 0.001 g•dm−3. In solution containing Cr3+, it is presumed that Cr(OH)3 formed at cathode layer suppresses the Ni deposition, resulting in some codeposition of NiO and Ni(OH)2 with Ni, which causes the decrease in current efficiency and lightness of Ni. On the other hand, in solution containing SO42−, the current efficiency of Ni somewhat decreased at SO42− concentration above 50 g•dm−3, and significantly decreased above 100 g•dm−3. The lightness of deposited Ni somewhat increased at SO42− concentration of 20 g•dm−3, and greatly increased above 20 g•dm−3. Since the overpotential for Ni deposition increases with increasing concentration of SO42−, the surface of deposited Ni becomes smooth, resulting in increase in lightness.
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