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Volume 80, Issue 1
Displaying 1-15 of 15 articles from this issue
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Special Issue on Frontier Researches Related to Nano/Microstructure, Microstructure Control and Mechanical Properties of Materials
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Kazuhiko Yamamoto, Ryo Murakami2015 Volume 80 Issue 1 Pages 1-6
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: November 06, 2015JOURNAL FREE ACCESSMicrostructure of NdFeB ternary alloy for magnet has a strong influence on pulverization, orientation in magnetic field and sintering in the production process, therefore magnetic properties of NdFeB sintered magnets strongly depend on microstructure of starting alloy. So it is very important to optimize the microstructure of starting alloy. In this study the mechanism of microstructure formation by strip casting method was investigated. Nd14.65Febal.B6.11 compounds were prepared by vacuum induction furnace in Ar atmosphere and casted onto φ150 mm water cooled roll. Thickness of obtained strip were 200-500 μm, each batch of compounds was around 2 kg. Effects of 1) surface conditions of copper roll, 2) surface velocity of roll and 3) roll materials with different thermal conductivity on microstructure of strip were investigated.
Through this study, following results were found, 1) grain size was able to be controlled by the nucleation site depending on surface conditions and the thermal conductivity of roll material, 2) dendrite size was controlled by the growth rate of solid phase and the relaxation of solute condensing around solid-liquid interface due to traveling of solid phase in puddle. Based on the obtained results, nucleation of solid phase in strip cast samples was also discussed.
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Overview
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Takashi Nagoshi, Tso-Fu Mark Chang, Masato Sone2015 Volume 80 Issue 1 Pages 7-12
Published: 2015
Released on J-STAGE: December 25, 2015
JOURNAL FREE ACCESSCompression and tensile testing of electrodeposited nickel films with micron-sized specimens are reviewed. Our developed fabrication method enabled to shape specimens without tapering. Accurate micro-testing method with uniformly shaped specimens revealed mechanical properties of electrodeposited metal. The micro-testing on nanocrystalline nickel plated by using electrodeposition method with supercritical carbon dioxide showed very high strength, which increased with decreasing sample size. The results indicate grain boundary mediated deformation of electrodeposited nanocrystalline nickel.
Fig. 1 Fullsize ImageSchematic and corresponded SEM images in the process of pillar fabrication.View full abstractDownload PDF (2953K)
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Hirofumi Inoue2015 Volume 80 Issue 1 Pages 13-21
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: November 06, 2015JOURNAL FREE ACCESSBendability of sheet metals is strongly affected by crystallographic orientation, and it was recently found that the bendability had a correlation with the Taylor factor in Al-Mg-Si and Cu-Ni-Si alloy sheets. This paper has proposed an analytical method for predicting in-plane anisotropy of bendability in polycrystalline face-centered cubic metal sheets by using the mean value of Taylor factors for all orientations in the space of the Euler angles. The calculation was performed on the assumption that a strain condition at the convex surface during bending deformation is close to plane strain tension. Using various ideal orientations with Gaussian distribution or various real textures of annealed aluminum or copper alloys, the normalized Taylor factor, which was defined as a ratio of the mean Taylor factor for a textured material to that for a randomly oriented one, was compared with some known experimental data on bendability at directions of 0° and 90° to the rolling direction. The results clearly showed that bendability was better at the bending direction with a lower normalized Taylor factor. Since the formation of shear bands at the sheet surface causes deterioration of bendability, the present analytical method based on the normalized Taylor factor has an advantage in predicting the bendability at arbitrary directions in a sheet, if textures of metal sheets are measured on the surface without polishing by means of X-ray diffraction.
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Takashi Ito, Yoji Mine, Masaaki Otsu, Kazuki Takashima2015 Volume 80 Issue 1 Pages 22-26
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: November 06, 2015JOURNAL FREE ACCESSA scanning white-light interferometry (SWLI) technique was used to image the surface topography and measure the in-plane strain in micrometre-sized structures subjected to uniaxial tensile deformation. This technique was applied to observing the macro and local deformation behaviours in micrometre-sized Au specimens. Reproducible stress-strain curves were successfully obtained using SWLI during the intermittent tensile tests. The local strain distribution was also calculated from the movement of natural gauge marks that are characteristic of triangular elements. Combining this micro-tensile test with orientation imaging microscopy enables crystal plasticity of mesoscale structures to be revealed.
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Hideki Hosoda, Takafumi Hori, Tomohiko Morita, Akira Umise, Masaki Tah ...2015 Volume 80 Issue 1 Pages 27-36
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: November 27, 2015
JOURNAL FREE ACCESSIn order to develop high performance biomedical shape memory alloy having both good biocompatibility and high X-ray radiography resolution, effects of Al and Cu contents on the martensitic transformation, microstructure and mechanical properties of AuCuAl ternary alloys were studied. Differential scanning calorimetry revealed that the martensitic transformation start temperature decreased with a rate of −7 K/mol%Al in the Au-30 mol%Cu-Al alloys. Besides, the Ms increased with a rate of 18~53 K/mol%Cu in the Au-Cu-15~20 mol%Al alloys in the Cu-poor side of stoichiometry, while the Ms was almost constant in Cu-rich side. By taking into account of the estimated defect structures, the number of Au-Al atomic bonds is important for the stabilization of the parent β phase. Corresponding microstructural change due to the martensitic transformation was confirmed by optical microscopy. Vickers hardness of the Au-30 mol%Cu-Al alloys decreased with increasing Al content, and a minimum was reached at 20~25 mol%Al and then the Vickers hardness increased at 25 mol%Al. The alloys at a limited composition range around Au-30~31 mol%Cu-14~15 mol%Al possessed both high strength and ductility in addition to pseudoelasticity, while the other alloys exhibited poor ductility.
Fig. 10 Fullsize ImageStress-strain curves of all the alloys tested at room temperature.View full abstractDownload PDF (3511K) -
Kazuki Endoh, Masaki Tahara, Tomonari Inamura, Hee Young Kim, Shuichi ...2015 Volume 80 Issue 1 Pages 37-44
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: November 27, 2015
JOURNAL FREE ACCESSThe effects of Zr addition on the mechanical, shape memory and superelastic properties of Ti-5Mo-3Sn (mol%) based alloys were investigated with Zr content up to 24 mol%. The parent bcc phase was stabilized with increasing Zr content, and the volume fraction of the ω phase seemed independent of the Zr content. The ultimate tensile strength and fracture strain increased with increasing Zr content up to 6 mol%Zr, however, the alloy became brittle with further addition of Zr content over 8 mol%. Young's modulus was low around 37~38 GPa when Zr content was 2~6 mol%. Shape memory effect was confirmed when Zr content was less than 5 mol%, and the superelasticity appeared in 6 mol%Zr-added alloy with the good shape recovery strain of 4.3%. When the Zr addition exceeded 6 mol%, the slip deformation occurred. The slip stress was raised by Zr addition with a rate of 9.5 MPa/mol%Zr in the alloys containing 2~6 mol%Zr. It is concluded for Ti-5Mo-3Sn based alloys that Zr addition is effective to improve the mechanical properties without degradation of lattice transformation strain, and that good room-temperature superelasticity appears in the Ti-5Mo-3Sn-6Zr alloy.
Fig. 8 Fullsize ImageStress-strain curves obtained at room temperature for (a) 0Zr, (b) 2Zr, (c) 4Zr, (d) 6Zr and (e) 8Zr. (f) The definition of each shape recovery strain.View full abstractDownload PDF (3154K) -
Effect of Annealing Temperature on Texture Formation of Ti-4Au-5Cr-8Zr Biomedical Superelastic AlloyYuri Shinohara, Masaki Tahara, Tomonari Inamura, Hideki Hosoda2015 Volume 80 Issue 1 Pages 45-50
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: November 27, 2015JOURNAL FREE ACCESSThe effect of annealing temperature on texture formation associated with superelastic behavior is clarified of Ti-4Au-5Cr-8Zr biomedical alloy in which Ti3Au precipitates at 973 K and 1073 K but does not precipitate at 1173 K. A Ti-4Au-5Cr-8Zr alloy ingot was cold-rolled with a reduction up to 98% in thickness followed by annealing at 973, 1073 and 1173 K for 1.8 ks. It was found that the as-rolled alloy and the alloy annealed at 973 K exhibit {112}β〈110〉β rolling texture, while the alloys annealed at 1073 K and 1173 K exhibit {001}β〈110〉β recrystallization texture regardless of Ti3Au precipitates. {001}β〈110〉β texture develops stronger in the alloy annealed at 1173 K compare with the alloy annealed at 1073 K. This is one of the reasons why alloy annealed at 1173 K shows larger shape recovery strain than the alloy annealed at 1073 K when tensile strain is applied along the rolling direction.
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Shiho Yamamoto, Kyosuke Yoshimi, Joungwook Kim, Kentaro Yokoyama2015 Volume 80 Issue 1 Pages 51-59
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: November 27, 2015JOURNAL FREE ACCESSTo evaluate the effects of microstructure on the high-temperature strength of TiC-added Mo-Si-B (MoSiBTiC) alloys, high-temperature compressive behavior was investigated for Mo-5.0Si-10.0B-7.5TiC (70Mo) and Mo-5.0Si-10.0B-10.0TiC (65Mo) (at%) alloys produced by arc-melting and tilt-casting. The cast ingots were heat-treated at 1800℃ for 24 h. In the stress-strain curves, the flow stress of both the alloys reached a compressive peak stress immediately after yielding and then gradually decreased with increasing strain. The flow-stress deterioration was relatively smaller for 70Mo than for 65Mo over the test temperature range. The strain-rate sensitivity of the peak stress was very small, and slightly increased with temperature from 0.05 at 1300℃ to 0.17 at 1500℃ for 70Mo and from 0.08 at 1300℃ to 0.19 at 1600℃ for 65Mo. From microstructure observations, the followings were found: i) there was no cracking in Mo solid solution and (Mo, Ti)2C phases (suggesting good deformability) through all the test conditions, ii) at and below 1400℃, (Ti, Mo)C phase fractured in a large strain region at all the examined strain-rates, and iii) T2 phase severely cracked even at a small strain depending on temperature and strain-rate. Such differences in the deformation properties of the constituent phases would control the high-temperature mechanical performance of the MoSiBTiC alloys.
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Kyosuke Ueda, Tatsuya Kobayashi, Takayuki Narushima2015 Volume 80 Issue 1 Pages 60-65
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: November 27, 2015JOURNAL FREE ACCESSThe microstructure and mechanical properties of the α+β type Ti-V-O alloys with high oxygen content were investigated. Ti-(0~10)mass%V-(0.5, 0.75, 1.0)mass%O alloy ingots were prepared using arc melting and hot rolling at 1373 K and 1073 K. The alloys were heat-treated at temperatures varying from 923 K to 1323 K for 3.6 ks under Ar flow. The β transus of the alloys was experimentally determined, and its value decreased with increasing V content and decreasing oxygen content in the alloy. Athermal ω was detected in the alloys with 6, 8 and 10 mass%V content and 0.5, 0.75 and 1 mass%O content after heat treatment at low temperatures in the range of 923 to 1123 K, wherein the V content in the β phase was higher than 12 mass%. The formation of the athermal ω led to the increase in hardness and decrease in the elongation and reduction of area of the alloys. Based on the investigation results, it was suggested that the Ti-4 mass%V-(0.5~0.75)mass%O alloy had an excellent balance between strength and ductility.
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Bo-Lun Zheng, Takashi Nagoshi, Tso-Fu Mark Chang, Hideki Hosoda, Tatsu ...2015 Volume 80 Issue 1 Pages 66-70
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: November 27, 2015
JOURNAL FREE ACCESSIn this paper, we fabricated two kinds of micro-sized pillars with a size of 10 μm×10 μm×20 μm from Al-Mg alloy with large grains by focused ion beam. One pillar is single crystalline with crystal orientation of [023] and the other is bi-crystalline with [023] and [225] crystal orientations. We conducted micro-compression tests for the two kinds of pillar. The mechanical testing of bi-crystalline pillar show stronger work-hardening than that of the single crystalline pillar. This could come from an increasing of deformation resistance by the grain boundary in bi-crystal. The strong sliding traces in deformed single crystalline pillar corresponded to (111)[101] slip system. It was observed in deformed bi-crystalline pillar that (111)[101] slip system was activated on the compression process and the sliding propagated to another slip system in other grains.
Fig. 5 Fullsize ImageSEM images of (a) single crystalline pillar A and (b) bi-crystalline pillar B after testing.View full abstractDownload PDF (1710K) -
Akira Umise, Tomohiko Morita, Takahumi Hori, Kenji Goto, Hiroyasu Kane ...2016 Volume 80 Issue 1 Pages 71-76
Published: 2016
Released on J-STAGE: December 25, 2015
Advance online publication: December 11, 2015
JOURNAL FREE ACCESSAlthough AuCuAl shape memory alloys are hopeful as advanced functional biomaterials exhibiting shape memory effect and good X-ray radiography, the limited ductility in polycrystalline materials is a drawback for practical applications. In this study, effects of quaternary elements (B, Ti, Zr, Cr, Mn, Fe, Zn, In and Sn) on martensitic transformation start temperature (Ms) and mechanical properties are investigated. It was found that (1) Mn, Fe, In and Sn additions decrease Ms and that (2) B, Ti, Zr, Cr and Zr additions do not affect or slightly increase Ms. Among the quaternary additions investigated, only Fe addition drastically improves ductility. Therefore, Fe is concluded to be the effective additional element to bring both sufficiently low Ms and ductility to AuCuAl alloys.
Fig. 6 Fullsize ImageStress-strain curves of AuCuAl quaternary alloys tested at room temperature. Note that tensile test could not be carried out for In alloy and Sn alloy due to their brittleness.View full abstractDownload PDF (2259K) -
Hideki Hosoda, Takuya Ishigaki, Yuri Shinohara, Tomonari Inamura2015 Volume 80 Issue 1 Pages 77-84
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: December 11, 2015
JOURNAL FREE ACCESSIn order to develop new functional biomaterials, the Zr-Au alloy system was focused and a Zr-9 mol%Au near-eutectoid alloy was used in this work. Effect of solution treatment and aging treatment temperatures on phase constituent, microstructure and Vickers hardness was investigated. It was found that Zr-9 mol%Au is a hypereutectic composition and experimental results in this work are not in agreement with the experimental phase diagram reported by Lomello-Tafin et al., but in good agreement with the calculated phase diagram reported Su et al. The major apparent phase was hcp αZr regardless of the heat treatment condition and Zr3Au second phase precipitated when heat-treated at 1173 K or lower temperatrues. The Vickers hardness value was HV503 after the solution treatment at 1273 K, but became lower with increasing the amount of micrometer-size Zr3Au precipitates. The hardness of this alloy was mainly due to the amount of the solute Au in αZr matrix. However, the alloy was slightly hardened by aging at 673 K due to the formation of submicron-meter-size fine Zr3Au precipitates.
Fig. 11 Fullsize ImageMicro Vickers hardness as a function of aging temperature for specimens solution treated at 1273 K (ST1273K specimens) and 1173 K (ST1173K specimens).View full abstractDownload PDF (5856K) -
Hirotaka Kawabe, Tomonari Inamura, Hideki Hosoda2015 Volume 80 Issue 1 Pages 85-91
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: December 11, 2015
JOURNAL FREE ACCESSIn order to quantitative evaluation of micro strain which is close to the resolution of images, a novel evaluation method using three dimensional microstructure images is proposed in this study, especially for the purpose to use in-house micro-focused X-ray tomography apparatus with the resolution of 1-5 μm. The evaluation method is composed of two parts. One is a conventional calculation method to evaluate deformation and the other is a quantitative evaluation of error which is generated by apparatus resolution. By applying this method to NiMnGa/silicone composite under 5% compression strain, 6.4±1 μm deformation of NiMnGa particle is determined under the conditions of 6 specific points and the apparatus resolution of 1.67 μm. Then, the present evaluation method is concluded to be the useful and strong calculation way for the quantitative understanding of resolution-level local-micro deformation, especially based on in-house micro-focused X-ray computed tomography.
Fig. 2 Fullsize ImageA schematic figure showing the occurrence of measurement error caused by apparatus resolution: (a) real shape, (b) image obtained by apparatus and (c) smoothed image where white circle is true specific point position and black circle is the measured point obtained in image.View full abstractDownload PDF (869K) -
Shunichi Nakayama, Kyosuke Yoshimi2015 Volume 80 Issue 1 Pages 92-101
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: December 11, 2015JOURNAL FREE ACCESSZrC-added Mo-Si-B alloys were prepared by arc-melting. After heat-treatment at 1800℃ for 24 h, their density and elastic moduli were measured, and their microstructure was evaluated. Moreover, high-temperature compression tests at 1400℃ and four-point bending tests with a Chevron notch at room temperature were conducted to investigate their mechanical properties. The primary phase was Mo solid solution (Moss) or ZrC depending on Mo/ZrC compositional ratio. After the primary phase crystallization, Mo2B, Mo5SiB2 (T2), Moss+ZrC eutectic, Moss+T2 eutectic and/or Moss+Mo3Si+T2 eutectic were crystallized out during solidification. Mo2B and/or Mo3Si dissolved during the heat treatment in some alloys. The ZrC-added Mo-Si-B alloys had higher high-temperature strength compared with the ternary Mo-Si-B alloys even though ZrC-added Mo-Si-B alloys contained less volume fraction of the T2. Besides, the ZrC-added Mo-Si-B alloys exhibited better fracture toughness than that of ternary Mo-Si-B alloys, reaching 20.2 MPa(m)1/2. Therefore, this study found that ZrC plays a significant role in improving high-temperature strength and fracture toughness in Mo-Si-B alloys.
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Hiromoto Kitahara, Masayuki Tsushida, Shinji Ando2015 Volume 80 Issue 1 Pages 102-107
Published: 2015
Released on J-STAGE: December 25, 2015
Advance online publication: December 11, 2015
JOURNAL FREE ACCESSMagnesium single crystals with different orientations were applied to three-point bending tests, and the bending deformation behavior was investigated. When the basal plane is parallel to the neutral plane, the specimens deformed due to basal slips. The specimens show gull-shape after deformation. On the other hand, when the neutral plane and the axis were parallel to (1120) and [1100], the specimen deformed due to {1012} twinning. However, it broke after a few percent of deformation, and then it showed V-shape. The specimen, whose neutral plane and axis are (1120) and [0001] also deformed due to basal slips. Relationship between bending yield stress of the specimens and CRSS of basal slip, or {1012} twin was discussed.
Fig. 7 Fullsize ImageOptical micrographs of (a) appearance of C specimen, (b) {1012} twins and a crack observed from (c) [0001] and (d) [1120] after the bending test.View full abstractDownload PDF (3904K)
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