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Volume 77, Issue 10
Displaying 1-12 of 12 articles from this issue
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Regular Article
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Masato Wakeda, Hajime Kimizuka, Shigenobu Ogata2013 Volume 77 Issue 10 Pages 409-414
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSAtomistic details of the interaction between screw dislocation and substitutional solute Si in Fe-Si alloy was investigated by atomistic modeling method. We developed an embedded atom method (EAM) potential for Fe-Si interaction based on the density functional theory calculations and then evaluated the interaction energy between Si and screw dislocation using the developed potential. The interaction energy is found to become larger as the Si atom approaches the screw dislocation. This indicates that attractive driving force acting between the Si atom and screw dislocation can lead to the athermal resistance. Using Nudged Elastic Band (NEB) method, we computed the energy barrier for screw dislocation glide associated with double kink formation, and found that the energy barrier is reduced by nearby existing Si atom. These results suggest that solute Si causes both solid-solution hardening and softening in Fe-Si alloys.
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Masayoshi Ichigo, Koshi Takenaka2013 Volume 77 Issue 10 Pages 415-418
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSPlastics have beneficial features of light weight and high workability, but their large thermal expansion emerges as a shortcoming for which reduction is desired in highly advanced industries. The negative thermal expansion (NTE) of antiperovskite manganese nitrides is greater than −30 ppm/K in α (coefficient of linear thermal expansion), which is several to ten times as large as that of conventional NTE materials. The giant NTE of the manganese nitrides can compensate or control large thermal expansion of plastics by forming composites. We attempt to make the fine-grained NTE manganese nitrides for thermal expansion control of light transmitting plastics. In the fine-graining process, NTE of manganese nitrides changed because of a change in the chemical composition. A technique to control NTE and grain size simultaneously is necessary for the manganese nitride filler.
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Haruki Yamane, Masanobu Kobayashi2013 Volume 77 Issue 10 Pages 419-423
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSThe influence of two-dimensional nano-structures on magnetic properties has been investigated in perpendicular antiferromagnetically coupled (AFC) Co80Pt20 stacked films. The AFC-samples consisted of [Co-Pt(10 nm)/Ru(0.46 nm)/Co-Pt(5 nm)] stacked layers, and the magnetization of the 5-nm-thick bottom Co-Pt layers was firstly reversed by AF-coupling. Hexagonal arrays of dots and holes were formed on both (top and bottom) Co-Pt layers and only on the top Co-Pt layer. The interlayer exchange coupling between the top and bottom Co-Pt layers across very thin Ru interlayer of 0.46 nm in thickness was kept even after the nanofabrication of about 100 nm in diameter. The coercivity of dot arrays markedly increased with a decrease in dot diameter, while the magnetic properties of hole arrays were less influenced by the nanoscale patterning. The magnetization rotation of AFC-samples with the patterned top layer changed from multiple to continuous reversal processes with decreasing in patterning size. For the top layer patterned sample, the minor loop shift of the 100-nm-dot arrays decreased from 240 to 140 kA/m, while the 100-nm-hole arrays showed almost the same strength of interlayer exchange coupling compared with that of continuous film prior to patterning.
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Shigeru Saito, Toshiyuki Takashima, Katsumi Miyama, Toshio Narita, Tai ...2013 Volume 77 Issue 10 Pages 424-429
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSCompositions with tie-lines between the χ, σ, γ, α, and Nb(Cr, Re)2 phases in a ternary Re-Cr-Nb system were investigated at 1500℃ by heat-treating various ternary Re-Cr-Nb alloys in vacuum for 2 h and 220 h. The microstructures of the Re-Cr-Nb alloys that had been water-quenched after heating were observed and their Re, Cr and Nb concentration profiles were measured using an electron probe micro-analyzer (EPMA).
The tie-line compositions (at%) of each phase at 1500℃ were experimentally determined, and an isothermal phase diagram was constructed. The χ phase tie-lined with the α phase (26.4 at%Re, 70.0 at%Cr, and 3.6 at%Nb) consists of 42.7 at%Re, 40.8 at%Cr, and 16.5 at%Nb. The α phase tie-lined with Nb(Cr, Re)2 phase (28.1 at%Re, 41.9 at%Cr, and 30.0 at%Nb) consists of 24.6 at%Re, 71.2 at%Cr, and 4.2 at%Nb. The solubility limits of Re in the γ phase has 44-45 at%Re, as the Cr contents increased (i.e., Re contents decreased) in the γ phase, the Cr contents in the χ phase with a tie-line with the γ phase increased from 1.8 at%Cr to 9.8 at%Cr. The solubility limits of Nb in the σ phase tie-lined with the χ phase are 2 at%Nb.
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Compression Properties of Al/Al-Mg-Si/Al-Si-Cu Alloy Three-Layered Functionally Graded Aluminum FoamKousuke Saito, Yoshihiko Hangai, Takao Utsunomiya, Osamu Kuwazuru, Soi ...2013 Volume 77 Issue 10 Pages 430-434
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSAluminum foam is a multifunctional material with a light weight and a high energy absorption. In this study, an A1050(pure Al)-A6061(Al-Mg-Si)-ADC12(Al-Si-Cu) aluminum alloy three-layered-structure functionally graded (FG) aluminum foam was fabricated by the friction stir welding (FSW) route. The pore structures and elemental Cu content of the fabricated A1050-A6061-ADC12 FG aluminum foam were observed nondestructively by X-ray CT inspection and Electron Probe Microanalysis (EPMA), respectively. It was shown that three-layered A1050-A6061-ADC12 FG aluminum foam can be fabricated with different pore structures and elemental Cu contents in each layer. The compression properties and deformation behavior of the A1050-A6061-ADC12 FG aluminum foam were obtained by a compression test. It was shown that the fabricated A1050-A6061-ADC12 FG aluminum foam exhibited three different deformation stages and three plateau regions corresponding to the pore structures and types of aluminum alloy in each layer.
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Akari Yoshida, Yoji Miyajima, Susumu Onaka2013 Volume 77 Issue 10 Pages 435-439
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSChanges in microstructure of a Cu single crystal by severe plastic deformation along a crystallographically asymmetric direction were observed. Plate-like specimens with (15 12 5)[9 10 3] orientation cut from the single crystal were deformed by rolling and accumulative roll-bonding. When the logarithmic equivalent strain εeq of rolling was 0.9, rotation of crystal orientation to (2 1 1)[1 1 1] without orientation splitting was observed inside the specimens. Although orientation splitting occurred near surfaces of the specimens, the band-like regions with near (2 1 1)[1 1 1] were still observed when εeq was 3.5. When εeq was 5.0, ultrafine-grained structure similar to that in severely deformed polycrystalline Cu was observed.
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Ken Kimura, Satoshi Hirose, Kohsaku Ushioda, Masaharu Hatano, Akihiko ...2013 Volume 77 Issue 10 Pages 440-447
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSIn high purity ferritic stainless steel having strong {111}〈112〉 texture, the occurrence of surface roughening after deep drawing cup test depends on the way of taking blanks. However, the cause has not been clarified. In this study, the mechanism was examined in two ways. In the first method heterogeneous deformation behavior was examined by crystal plasticity (CP) analysis in which an adjacent two grains model was assumed. In the case that showed higher surface roughening, the direction of crystal rotation across the grain boundaries (GB) was almost the same and the dislocation density in the vicinity of the GB was higher than that in the area apart from the GB. In the case that showed lower surface roughening, crystals rotated in inverse direction across the GB and the dislocation density in the vicinity of the GB was lower than that in the area apart from the GB. In the second method the distribution of strain taking into account surface roughening was examined by EBSD. In the specimen with higher surface roughening, the area with high dislocation densities predicted by Kernel Average Misorientation (KAM) value was recognized along the GB and the convex region tended to coincide with the area with high dislocation densities. These results obtained from CP and EBSD analyses imply that the surface roughening depending on the way of taking blanks is associated with the strong {111}〈112〉 texture and is caused by the accumulated dislocation density along the grain boundaries.
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Shunsuke Taniguchi, Rumi Kitazawa, Yoshihisa Tanaka, Makoto Yoshida, S ...2013 Volume 77 Issue 10 Pages 448-454
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSFor magnesium alloy ZK60 with different heat treatments, controlled plastic strain amplitude fatigue tests were conducted. Effects of twinning and aging treatments on fatigue process were investigated by analyzing the second derivative of hysteresis half-loop. It is found that during compression the convex peak appears at the strain where twinning begins. It is also found that during tension the convex peak appears at the strain where detwinning begins and the concave peak appears at the strain where slip begins to be predominant. Analyzing the strain at the convex peak in compression at the plastic strain amplitude of 6×10−3, for solution treated material and over-aged material twinning hardens with increasing cycle. On the other hand, for T6 material twinning softens from 5 cycle to Nf/5 cycle and then hardens from Nf/5 cycle to Nf/2 cycle. It was suggested that residual twins cause twinning hardening. It was also suggested that cut and dissolution of rod-like precipitates should cause twinning softening. Due to different states of precipitates of materials, the twinning softening appeared for only T6 material at the plastic strain amplitude of 6×10−3. Moreover, the softening were not found for T6 material under the plastic strain amplitude of 4×10−3.
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Gen-ichiro Nagatani, Rumi Kitazawa, Makoto Yoshida, Susumu Horibe2013 Volume 77 Issue 10 Pages 455-460
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSIt is well known that creep at room temperature remarkably occurs in alpha-Ti alloys. Cyclic creep also appears. Moreover, Ti alloys have different crystal structures and various mechanical properties. Although the cyclic creep behavior and the cyclic softening behavior have been studied, integrated effect of them on fatigue life has not been clarified yet. In this study, fatigue behavior under stress ratio R=0, on Ti alloys of three crystal structures, is investigated. Influence of the cyclic creep and fatigue damage, and influence of the crystal structure to fatigue life are examined. As the results, it is found that as to the alpha-Ti, creep is the dominant damage factor. On the other hand, as to the beta-Ti alloy, fatigue is the dominant damage factor. As to the alpha+beta-Ti alloy, both creep and fatigue are the dominant damage factors (intermediate type). Furthermore, it is found that the area ratio and grain diameter of alpha phase, the spacing between different phases, should influence on cyclic creep strain rate.
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Junya Goto, Takatoshi Kakimoto, Shinpei Fujii, Keiichi Koyama2013 Volume 77 Issue 10 Pages 461-465
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSFirst-principles band-structure calculations have been carried out for CoMnSb and MnCoSb, where the Co atom is substituted for Mn(I) and Mn(II) in Mn2Sb, respectively. Among several magnetic structures, a ferromagnetic (F) state and a kind of antiferromagnetic (AF) state only converge. For both magnetic states, the Co atom energetically prefers the Mn(I) site to the Mn(II) site, and the magnetic moments of Co on Mn(I) have a parallel coupling with those of Mn(II). The lattice constant c (a) shrinks (expands) from F to AF states. These are in good agreement with experimental trends. Furthermore, our result shows that the optimization of the ratio c/a (lattice distortion) is crucial to determine a preferable magnetic order and that the optimization of the atomic positions of Mn(II) and Sb is also crucial.
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Takahiro Mineta, Seiji Miura, Toshiji Mukai, Mikito Ueda, Tetsuo Mohri2013 Volume 77 Issue 10 Pages 466-472
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSIn Mg alloys, the most favorable deformation mechanism is the basal slip, and extension twinning also contributes to plastic deformation. Other mechanisms such as prismatic slips, pyramidal slips and twinning except for extension twinning scarcely occur. However, these slip systems also contribute to the plastic deformation of poly crystal Mg alloys, so the determination of CRSS of such non-basal slip systems are inevitable as a basis for the prediction of the deformation behavior of poly-crystal Mg alloys. Because of the difficulty of the evaluation of CRSS for non-basal slip by conventional compression test, newly designed “Pure shear test” is applied to evaluate the CRSS of the prismatic slip Mg alloy single crystals containing Y. Also a modification of Bridgman method using LiF+LiCl is attempted to obtain a pure-Mg single crystal.
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Yasuhiro Nagatomo, Hisao Esaka, Kei Shinozuka2013 Volume 77 Issue 10 Pages 473-478
Published: 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSThe volume fractions of primary β-Sn in Sn-Ag alloys after solidification have been measured changing the holding time in solid-liquid region. Sn-2.32 mass%Ag alloy has been used in this experiment. The specimen was cooled at a constant cooling rate of 3℃/min in Ar atmosphere from the liquid phase. After observing the recalescence by the thermocouple inserted in the crucible, the specimen was held in solid-liquid region. Changing the holding time, the volume fraction of primary β-Sn on the longitudinal cross section has been measured. The volume fraction of primary β-Sn was larger than the expected from lever rule, in case of short holding time. However, it decreased with increasing the holding time and approached to the value estimated by lever rule. Moreover, the size of primary β-Sn increased as the holding time increased. It is clear that the volume fraction of primary β-Sn depended on the holding time in solid-liquid region and it takes time to come to equilibrium.
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