| 1. |
Xiaohuan Chen, Yan Zhang, Fang Zhao, Mingqiang Tang, Mingliang Xiang, Juntao Huo, Meng Gao, Yaocen Wang, Noriharu Yodoshi, Liyuan Zhang, Junqiang Wang, Fabrication and excellent performance of amorphous FeSiBCCr/organic-inorganic hybrid powder core, Journal of Non-Crystalline Solids, 10.1016/j.jnoncrysol.2023.122482, 616, 2023.09, Soft magnetic composites (SMCs) are widely used in relevant inductance components in power and electronic fields. The development of high frequency devices requires SMCs to exhibit good insulation and excellent soft magnetic properties. The insulation coating for SMCs is crucial, and it is necessary to ensure that the coating thickness is uniform and maintains excellent adhesion to the powder. In the present work, a novel and efficient solution for the formation of insulating coatings, i.e. phytic acid/silane (denoted as PAS) organic-inorganic hybrid solution, was prepared by the condensation reaction between PA and γ-(2,3-epoxypropoxy) propyl trimethoxy silane. The FeSiBCCr@PAS powder with a core-shell structure has been successfully prepared through chemical reaction in a modified PAS solution. The effects of insulating coating content on the magnetic and mechanical properties of FeSiBCCr@PAS powder cores were systematically investigated. The PAS hybrid insulating coating can significantly improve the DC-bias performance and reduce the core loss. The optiomal powder core, which was prepared by using the powder coated with 3 g/L phytic acid, exhibits a minimum core loss (P50mT/1MHz) of 2979.2 mW/cm3, high effective permeability μe(0.1A/m) of 33.8, and superior DC-bias(100Oe) performance of 80.8%. Present work developed an effective method to prepare high performance powder cores with good soft magnetic and mechanical properties.. |
| 2. |
Ziyan Hao, Linzhuo Wei, Lei Gao, Yaocen Wang, Xiaojun Bai, Xing Tong, Xiaoyu Liang, Noriharu Yodoshi, Rie Umetsu, Yoshiyuki Kawazoe, Yan Zhang, Chongde Cao, Effect of P addition on soft magnetic properties of Fe–Si–B–P–Cu–C nano-crystalline alloys, Intermetallics, 10.1016/j.intermet.2022.107713, 151, 2022.12, The effect of P addition on the nano-crystallization of Fe81.5Si0.5B15.5-xPxCu0.5C2 (x = 0, 4.5, 7.5, 11 at.%) amorphous alloys under various heating rates has been studied. Appropriate P addition enhanced the thermal stability of Fe–Si–B–P–Cu–C amorphous alloys. The results also revealed that P addition could decrease the required critical heating rate for the low coercivity and improve the magnetic softness of annealed samples. Although as commonly found in most Fe-based nano-crystalline alloys, a small amount of P addition (4.5 at.%) could effectively help reduce the coercivity when a high heating rate was applied during nano-crystallization, the high heating rate failed to decrease the coercivity in 7.5 at.% P-added alloys and even reversely caused the deterioration of magnetic softness for excessive P addition (11 at.%). The unusual phenomenon in the alloy with 11 at.% P addition lies in the fast increase of diffusion rate with rising temperature and delayed nucleation, which are caused by the weakened bond energy and increased segregation energy, respectively. The results suggest that the improvement of magnetic softness for Fe-based nano-crystalline alloys through simply increasing the P addition would meet its ceiling, due to the limited decrease in coercivity and even increase through applying high heating rate with excessive P concentration. The understanding of P role on the nano-crystallization mechanism could contribute to the compositional design of high-performance soft magnetic Fe-based alloys with an acceptable heating rate in industry.. |
| 3. |
Ziyan Hao, Linzhuo Wei, Yaocen Wang, Yoshiyuki Kawazoe, Xiaoyu Liang, Rie Umetsu, Noriharu Yodoshi, Xing Tong, Weixing Xia, Yan Zhang, Chongde Cao, Effect of Si addition on the magnetic properties of FeNi-based alloys with L10 phase through annealing amorphous precursor, Journal of Alloys and Compounds, 10.1016/j.jallcom.2022.166029, 920, 2022.11, As a promising candidate of rare-earth free hard magnetic materials, L10-FeNi has been paid much attention in the last decades. However, it is difficult to be artificially fabricated due to its low thermal stability and sluggish diffusion ability of atoms below the crucial temperature of 320 °C. In this study, a promising method of annealing amorphous precursor was extensively developed through (Fe50Ni50)84−xSixP16 (x = 0, 4 at%) and (Fe50Ni50)86−xSixP14 (x = 2, 4, 8 at%) alloys. Especially, the effect of Si on the formation of L10 phase in annealed FeNi-based alloys was investigated and clarified. It is found Fe42Ni42P16 with a much low crystallization temperature could be an appropriate basic amorphous alloy for the formation of L10 phase. The addition of Si enhanced the thermal stability of Fe-Ni-P amorphous alloys. Interestingly, Si could stabilize the L10 phase in annealed samples and increase its disordering temperature above which L10-FeNi phase could deteriorate into soft magnetic phase. As expected, appropriate Si addition indeed improved the hard magnetic properties of the annealed alloys and samples with high coercivity above 900 Oe was obtained. Further Si addition would deteriorate the magnetic-crystalline anisotropy of L10 phase and decrease the coercivity of annealed Fe-Ni-Si-P alloys. Nevertheless, the results indicate that increasing the order-disorder transition temperature through element doping in L10 lattice would be a promising strategy for the massive formation of L10-FeNi like other ordered phases (i.e. L12-FeNi, L10-CoPt), and could substantively contribute to the artificial fabrication of FeNi-based rare-earth free magnets in future.. |
| 4. |
Hiroshi Nakajima, Akihiro Osako, Noriharu Yodoshi, Yoshiharu Yamada, Hirofumi Tsukasaki, Ken Harada, Yuki Sakai, Kei Shigematsu, Takumi Nishikubo, Masaki Azuma, Shigeo Mori, Magnetization Controlled by Crystallization in Soft Magnetic Fe-Si-B-P-Cu Alloys., Microscopy (Oxford, England), 10.1093/jmicro/dfac042, 2022.08, Soft magnetic materials have low coercive fields and high permeability. Recently, nanocrystalline alloys obtained using annealing amorphous alloys have attracted much interest since nanocrystalline alloys with small grain sizes of tens of nanometers exhibit low coercive fields comparable to that of amorphous alloys. Since nanocrystalline soft magnetic materials attain remarkable soft magnetic properties by controlling the grain size, the crystal grains' microstructure has a substantial influence on the soft magnetic properties. In this research, we examined the magnetic properties of Fe-Si-B-P-Cu nanocrystalline soft magnetic alloys obtained by annealing amorphous alloys. During crystallization, the observation findings reveal the correlation between the generated microstructures and soft magnetic properties.. |
| 5. |
Noriharu Yodoshi, Takahide Endo, Naoya Masahashi, Evaluation of Porosity in Gas-Atomized Powder by Synchrotron X-ray CT and Investigation of the Effect of Gas Species, MATERIALS TRANSACTIONS, 10.2320/matertrans.mt-y2021001, 62, 10, 1549-1555, 2021.10.  |
| 6. |
Y. Hirayama, M. Shigeta, Z. Liu, N. Yodoshi, A. Hosokawa, K. Takagi, Anisotropic Nd-Fe ultrafine particles with stable and metastable phases prepared by induction thermal plasma, JOURNAL OF ALLOYS AND COMPOUNDS, 10.1016/j.jallcom.2021.159724, 873, 2021.08. |
| 7. |
吉年 規治, 遠藤 嵩英, 正橋 直哉, シンクロトロン光X線CTによるガスアトマイズ粉末に含まれる気孔量評価およびガス種の影響調査, 粉体および粉末冶金, 10.2497/jjspm.68.167, 68, 5, 167-174, 2021.05. |
| 8. |
N. Ciftci, N. Yodoshi, S. Armstrong, L. Mädler, V. Uhlenwinkel, Processing soft ferromagnetic metallic glasses: on novel cooling strategies in gas atomization, hydrogen enhancement, and consolidation, Journal of Materials Science and Technology, 10.1016/j.jmst.2020.03.077, 59, 26-36, 2020.12, © 2020 Processing soft ferromagnetic glass-forming alloys through gas atomization and consolidation is the most effective technique to produce bulk samples. The commercial viability of these materials depends on commercial purity feedstock. However, crystallization in commercial purity feedstock is several orders of magnitude faster than in high purity materials. The production of amorphous powders with commercial purity requires high cooling rates, which can only be achieved by extending the common process window in conventional gas atomization. The development of novel cooling strategies during molten metal gas atomization on two model alloys ({(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 and Fe76B10Si9P5) is reported. Hydrogen inducement during liquid quenching significantly improved the glass-forming ability and soft magnetic properties of {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 powders. Spark plasma sintering experiments verified that amorphous rings could be produced regardless of the cooling strategies used. While the saturation magnetization was almost unaffected by consolidation, the coercivity increased slightly and permeability decreased significantly. The magnetic properties of the final bulk samples were independent of feedstock quality. The developed cooling strategies provide a great opportunity for the commercialization of soft ferromagnetic glass-forming alloys with commercial purity.. |
| 9. |
Lei Liu, Hiraku Oda, Tetsuhiko Onda, Noriharu Yodoshi, Takeshi Wada, Zhong Chun Chen, Microstructure and thermoelectric properties of higher manganese silicides fabricated via gas atomization and spark plasma sintering, Materials Chemistry and Physics, 10.1016/j.matchemphys.2020.122990, 249, 2020.07, © 2020 Elsevier B.V. Higher manganese silicides (HMS) powders were successfully prepared by a gas atomization technique. The gas atomized (GAed) powders showed spherical morphologies and a wide particle size distribution. No MnSi and Si phases were detected by XRD analyses, indicating that the high cooling rate during rapid solidification is effective in inhibiting the formation of second phases. When the GAed powders were consolidated by spark plasma sintering (SPS), the densified samples revealed almost the same phase composition as the powders and an isotropic feature. The contrast differences between different grains in backscattered electron images are believed to be associated with orientation differences. The HMS samples SPSed at different temperatures exhibited similar values of the Seebeck coefficient, but larger electrical conductivity and power factor were obtained in the sample SPSed at 1000 °C. Moreover, the HMS samples showed higher fracture toughness compared to those fabricated by a solid-state reaction and SPS process.. |
| 10. |
Rui Yamada, Noriharu Yodoshi, Naoyuki Nomura, Junji Saida, Akira Kawasaki, Uniformity of the glassy state of iron-based metallic glassy particles and reproducibility of fabricating microparts, Materials & Design, 10.1016/j.matdes.2020.108667, 191, 108667-108667, 2020.06, The uniformity of the glassy state of [(Fe Co ) Si B ] Nb metallic glassy particles prepared using our own developed technique, called the pulsated orifice ejection method (POEM), was investigated. Differential scanning calorimetry (DSC) results revealed that the thermal histories of the particles prepared from the same batch were almost identical. This suggested that the particles with the same size/volume possessed almost the same glassy state and had advantages as raw materials for microparts. The fabricated final product using our proposed process, termed as micro viscous flow processing, where a single particle is compressed with a precise jig under strictly controlled processing conditions, was confirmed to maintain a fully amorphous structure. DSC scans of each micropart traced nearly the same path, which indicated that their glassy states were still almost identical after processing. The precise control of the temperature and applied load enable the final products to achieve almost the same thermal histories and also geometric shapes. This is the first report that proves the high reproducibility of fabricating Fe-based metallic glassy microparts with high quality. Our proposed sequential process may shed light on a new fabrication technique of microparts using metallic glasses. 0.5 0.5 0.75 0.05 0.2 96 4. |
| 11. |
Hiroki Kurita, Kazuya Sakayanagi, Shoichi Kikuchi, Noriharu Yodoshi, Sophie Gourdet, Fumio Narita, Crack initiation behavior of titanium boride whisker reinforced titanium matrix composites during small punch testing, Material Design & Processing Communications, 10.1002/mdp2.80, 1, 4, 2019.08. |
| 12. |
Hiroki Kurita, Shiori Suzuki, Shoichi Kikuchi, Noriharu Yodoshi, Sophie Gourdet, Fumio Narita, Strengthening Mechanism of Titanium Boride Whisker-Reinforced Ti-6Al-4V Alloy Matrix Composites with the TiB Orientation Perpendicular to the Loading Direction, Materials, 10.3390/ma12152401, 12, 15, 2401-2401, 2019.07, We fabricated fully dense titanium boride (TiB) whisker-reinforced Ti-6Al-4V alloy matrix (Ti6Al4V-TiB) composites, with a homogeneous dispersion, a TiB orientation perpendicular to the loading direction (; two-dimensional random direction) and an intimate Ti/TiB interface without an intermediate interfacial layer in the Ti-6Al-4V alloy matrix, by spark plasma sintering. Microstructural analysis allows us to present the tensile properties of the Ti6Al4V-TiB composites with the theories for discontinuous fiber-reinforced composites. The Ti6Al4V-TiB 10 vol.% composite yielded a Young’s modulus of 130 GPa, an ultimate tensile strength (UTS) of 1193 MPa and an elongation of 2.8%. The obtained experimental Young’s modulus and UTS of the Ti6Al4V-TiB composites were consistent with the theoretical values estimated by the Halpin-Tsai and Shear-lag models. The good agreement between our experimental results and these models indicates that the TiB whiskers behave as discontinuous fibers in the Ti-6Al-4V alloy matrix.. |
| 13. |
Hiroki Kurita, Katsuyoshi Kondoh, Junko Umeda, Noriharu Yodoshi, Tensile Fracture of TiB Whisker Reinforced Ti Alloy Matrix Composites, Materials Science Forum, 10.4028/www.scientific.net/msf.941.1961, 941, 1961-1965, 2018.12, TiB whisker reinforced Ti alloy matrix (Ti–TiB) composites have attracted attention as the aerospace materials with their high specific mechanical properties for long time. However, strengthening mechanism of Ti–TiB composites has not been revealed because of the agglomeration and incomplete precipitation of TiB whiskers in the Ti alloy matrix yet. In this study, we addressed to fabricate fully-dense TiB whisker reinforced Ti-6Al-4V alloy matrix (Ti6Al4V–TiB) composites via powder metallurgical process, which have the microstructure to discuss their tensile properties with the theories for composite materials. The Young’s modulus and ultimate tensile strength of Ti6Al4V–10 vol% TiB composite were 130 GPa and 1193 MPa, respectively. Note that the elongation of Ti6Al4V–10 vol% TiB composite was approximately 2.8 % although the elongations of Ti–TiB composite have been reported are few (; less than 1%) due to the agglomeration of TiB whiskers in Ti matrix.. |
| 14. |
吉年規治, 無容器凝固法による高品位鉄系金属ガラス原料粒子の合成と1粒子の粘性流動加工プロセスによる高精度・高強度マイクロ部品の創製, 先端加工技術, 104, 16, 2018.04. |
| 15. |
Noriharu Yodoshi, Shunpei Ookawa, Rui Yamada, Naoyuki Nomura, Keiko Kikuchi, Akira Kawasaki, Effects of nanocrystallisation on saturation magnetisation of amorphous Fe76Si9B10P5, Materials Research Letters, 10.1080/21663831.2017.1398191, 6, 1, 100-105, 2018.01, © 2017 The Author(s). Amorphous Fe76Si9B10P5 particles were fabricated by a container-free solidification process and subsequent annealing, and their structural and magnetic properties were investigated by X-ray diffraction analysis, transmission electronic microscopy, and vibrating sample magnetometry. The annealing induced the nanocrystallisation of α-Fe and Fe-B compounds. The proportions of the different crystalline phases formed were dependent on the annealing temperature. The saturation magnetisation of the single particles was higher than that of the samples prepared by a conventional quenching process; this was attributable to the higher homogeneity of the nanocrystalline grains of the former as well as their higher α-Fe to Fe-B compound ratio. (Figure presented) IMPACT STATEMENT We have investigated single particles obtained by a container-free solidification process to gain deeper insight into their magnetic properties than is possible with samples obtained by conventional processes.. |
| 16. |
N. Yodoshi, S. Ookawa, R. Yamada, A. Kawasaki, A. Makino, Temperature dependency of viscosity of Fe76Si9B10P5 supercooled liquid and hetero-amorphous structure, Journal of Alloys and Compounds, 10.1016/j.jallcom.2016.04.032, 679, 164-168, 2016.09, © 2016 Elsevier B.V. All rights reserved. In this study, we evaluated the thermal stability and fragility of Fe76Si9B10P5 supercooled liquid by using micrometer-scale particles prepared via a container-less solidification process. After construction of time-temperature-transformation (TTT) diagram of crystallization by means of isothermal DSC under various temperatures, we could successfully measure the viscosity of the particles in the supercooled liquid region by employing the single particle compressive test (SPCT). It is revealed that the temperature dependency of viscosity cannot be well fitted by the Vogel-Fulcher-Tammann (VFT) formula but can be fitted by an Arrhenius plot. The Angell plot indicates that the apparent fragility is higher than that of SiO2 and the fabricated particles have hetero-amorphous structures composed of high-density nanoscale clusters dispersed uniformly in a glassy matrix phase.. |
| 17. |
Jian Luan, Parmanand Sharma, Noriharu Yodoshi, Yan Zhang, Akihiro Makino, Mechanically strong nanocrystalline Fe-Si-B-P-Cu soft magnetic powder cores utilizing magnetic metallic glass as a binder, AIP Advances, 10.1063/1.4944766, 6, 5, 2016.05, © 2016 Author(s). We report on the fabrication and properties of soft magnetic powder cores with superior mechanical strength as well as low core loss (W). Development of such cores is important for applications in automobiles/devices operating in motion. High saturation magnetic flux density (Bs) Fe-Si-B-P-Cu powder was sintered with Fe55C10B5P10Ni15Mo5 metallic glass (MG) powder in its supercooled liquid state by spark plasma sintering. The sintered cores are made from the nanocrystalline powder particles of Fe-Si-B-P-Cu alloy, which are separated through a magnetic Fe55C10B5P10Ni15Mo5 MG alloy. Low W of ∼ 2.2 W/kg (at 1T and 50 Hz), and high fracture strength (yielding stress ∼500 MPa), which is an order of magnitude higher than the conventional powder cores, were obtained. Stronger metal-metal bonding and magnetic nature of MG binder (which is very different than the conventional polymer based binders) are responsible for the superior mechanical and magnetic properties. The MG binder not only helps in improving the mechanical properties but it also enhances the overall Bs of the core.. |
| 18. |
N. Yodoshi, R. Yamada, A. Kawasaki, A. Makino, Evaluation of critical cooling rate of Fe76Si9B10P5 metallic glass by containerless solidification process, Journal of Alloys and Compounds, 10.1016/j.jallcom.2015.04.088, 643, S1, S2-S7, 2015.06, © 2015 Elsevier B.V. All rights reserved. We aim to prepare monodispersed and homogenous spherical particles of pure Fe76Si9B10P5 metallic glass with a low content of nucleation sites, and to evaluate the intrinsic glass-forming ability of Fe76Si9B10P5 alloys by containerless solidification. Monodispersed Fe76Si9B10P5 particles were successfully prepared by our originally developed pulsated orifice ejection method under He and Ar gas atmosphere. All obtained particles, with diameters ranging from 313 to 664 μm, were identified as single glassy or amorphous phases by X-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The critical cooling rate to form the fully glassy or amorphous phase was estimated in less than 550 K/s by a Newtonian cooling model. The results show that the Fe76Si9B10P5 alloy has sufficient glass-forming ability under restrained nucleation conditions.. |
| 19. |
Yan Zhang, Parmanand Sharma, Noriharu Yodoshi, Akihiro Makino, Production of a magnetic material with the ability to change from very soft to semi-hard magnetic, Journal of Applied Physics, 10.1063/1.4916812, 117, 17, 2015.05, © 2015 AIP Publishing LLC. Development and magnetic properties of an alloy that can change from very soft to semi-hard magnetic are reported. We found that as quenched ribbons of Fe75.3Pt8B12P4Cu0.7 alloy are amorphous by X-ray. Heat treatment in the temperature range of 400-450°C causes formation of many α-Fe grains in the amorphous matrix. Hard magnetic L10 FePt grains appear at ∼520°C. This alloy shows a high saturation magnetic flux density [Bs (≈ Ms)>1.55T] along with the ability to vary coercivity (Hc) from ∼25A/m to 11000A/m. The Hc can be increased further to more than 21000A/m, but at the expense of a significant decrease in Bs. The ability to control magnetic properties lies in a precise control over the soft and hard magnetic phases, which are strongly exchange coupled.. |
| 20. |
N. Yodoshi, R. Yamada, A. Kawasaki, A. Makino, Micro viscous flow processing of Fe-based metallic glassy particles, Journal of Alloys and Compounds, 10.1016/j.jallcom.2013.12.256, 615, S1, S61-S66, 2014.12, © 2014 Elsevier B.V. All rights reserved. Fe-based metallic glasses are difficult to plastically form into complex shapes in their supercooled liquid region because of their rather high viscosity and low thermal stability. In this study, we proposed a novel two-step fabrication process for micro components using viscous flow of an Fe-based metallic glass. First, we prepare mono-sized [(Fe0.5Co0.5)0.75 Si0.05B0.2]96Nb4 spherical particles with precisely controlled volumes that correspond to the desired micro component volume. It is essential that the prepared spherical particles be composed of a single glassy phase. Then, one prepared particle is die-pressed into one micro component under the supercooled liquid region. The main deformation mechanism is viscous flow and the micro hot-press apparatus was used to realize the optimal processing conditions for micro viscous flow. The processed micro gear maintained the fully glassy phase, resulting in excellent mechanical strength, up to 1125 HV on average by the Vicker hardness test. Crystallization of the material during processing has been discussed related to the process temperature and deformation rate using the model of Kaysser and Arzt.. |
| 21. |
N. Yodoshi, R. Yamada, A. Kawasaki, A. Makino, Stress relaxation behavior of Fe-Co-Si-B-Nb metallic glassy alloys in their supercooled-liquid state, Journal of Alloys and Compounds, 10.1016/j.jallcom.2014.05.006, 612, 243-251, 2014.11, Iron-based metallic glasses have attracted much attention for use as microscale components in many devices because they provide unique processability with nanoscale precision. Fe-based metallic glasses, however, do not have enough resistance against crystallization, and therefore their incubation time for crystallization is too short. To prevent crystallization, the processing temperature cannot be set too high within the supercooled-liquid region, and high processing speeds are required. Taking this into consideration, the viscoelastic properties were observed during the viscous-flow microprocessing of a single metallic glassy particle of [(Fe0.5Co0.5) 0.75Si0.05B0.2]96Nb4 metallic glass to identify its relaxation behavior of on the micrometer scale during a compressive test at 833 K. The relaxation behavior is found to be well described by the Kohlrausch-Williams-Watt model. The dependence of the ratio of the viscosity to the modulus of rigidity on the compressive speed during deformation was also investigated by constructing the master curve describing the behavior of the elasticity and viscosity fractions versus the apparent relaxation time. At a compressive strain rate of 4.5 × 10-2 s-1, the Fe-based metallic supercooled liquid behaved as a viscoelastic fluid, although at a compressive strain rate of 4.5 × 10 -3 s-1, its behavior was almost viscous. From the master curve, it can be concluded that the effect of the compressive speed on the ratio of the viscosity to the modulus of rigidity can clearly be observed, and the viscous-flow behavior of a [(Fe0.5Co0.5) 0.75Si0.05B0.2]96Nb4 metallic supercooled liquid can be predicted at any processing speed. © 2014 Elsevier B.V. All rights reserved.. |
| 22. |
N. Yodoshi, R. Yamada, A. Kawasaki, A. Makino, Interface observation of iron based metallic glassy powder in pressurized liquid phase sintered compaction, Euro PM 2014 Congress and Exhibition, Proceedings, 2014.11, To consolidate [(Fe0.5Co0.5)0.75Si0.05B0.2] 96 Nb4 metallic glassy powder to full density, a pressurized liquid phase sintering was employed, which was intended to promote a viscous flow deformation of solid particles and also to enhance the intergranular permeation of the liquid phase. Al-32.5wt.%Cu was chosen as a liquid phase component having low melting point. The mixed powders were sintered by induction heating furnace with heating rate of 200 K/min and applying pressure of 400 MPa for maintaining the amorphous phase. SEM and TEM observations shows the interfacial reaction layers were formed between metallic glassy phase and liquid phase. While this layer can contribute for to reinforce the fracture strength, the layer interferes with deformation of metallic glassy powders and also interferes with squeezing of liquid phase. This study report the interfacial microstructure between the powder particles by TEM observations.. |
| 23. |
N. Yodoshi, R. Yamada, A. Kawasaki, A. Makino, Pressurized liquid phase sintering of iron based metallic glassy powder with Al-Cu eutectic alloy, International Powder Metallurgy Congress and Exhibition, Euro PM 2013, 2013.10, The compressive fracture strength of the obtained metallic glass composite was found to be as high as 1820 MPa and the fracture w)as observed to be intragranulartype, suggesting a good bonding in the particle-binding phase interface.,To consolidate [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glass powder to full density, a pressurized liquid phase sintering was employed, which was intended to promote densification. Al-Cu eutectic alloy was chosen as a liquid phase component. However, the wettability of the glassy alloy with the AI-32.5wt%Cu alloy was revealed to be poor. Therefore, sintering pressure was applied to the compacts to promote a viscous flow deformation of glassy particles and also to enhance the intergranular permeation of the liquid phase. The liquid phase was found to fill completely the intergranular space of the powder compact, and the microstructure could be controlled by the punch displacement to squeeze out a part of the liquid phase from the compact.. |
| 24. |
山田 類, 吉年 規治, 川崎 亮, Fe系およびPd系金属ガラス球形粒子作製時の冷却速度と容器壁の影響, 日本金屬學會誌, 10.2320/jinstmet.77.139, 77, 4, 139-146, 2013.04, Preparation of Fe-based and Pd-based metallic glassy particles with a diameter of around 500 μm were investigated. Firstly, we measured the critical cooling rate of Pd42.5Cu30Ni7.5P20 metallic glass and our results showed that its critical cooling rate was about 0.4 K/s. Pd-based metallic glassy spherical particles with fully amorphous structure were successfully prepared by heating the samples on the Al2O3 substrate up to their melting points and cooling under the cooling rate of around 3 K/s. In contrast, [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glassy particles cannot be prepared by the same process. This seemed to be caused by a reaction between the Fe-based metallic glass and the Al2O3 substrate around its melting point. This result suggested that containerless solidification method is expected to be used to prepare Fe-based metallic glassy particles. We successfully prepared mono-sized spherical particles of [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glass by Pulsated Orifice Ejection Method (POEM) as an ideal process for Fe-based metallic glasses.
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| 25. |
N. Yodoshi, R. Yamada, A. Kawasaki, R. Watanabe, Evaluation of viscosity for Fe-based metallic glass in the supercooled liquid region by a single-particle compressive test, Scripta Materialia, 10.1016/j.scriptamat.2012.08.034, 67, 12, 971-974, 2012.12, A new method for determining the viscosity of the supercooled liquid region of metallic glasses by means of a single-particle compressive test (SPCT) is proposed. A spherical metallic glassy particle several hundred micrometers in diameter is uniaxially pressed using a precisely controlled micro-hot-pressing system. Assuming viscous flow of the material, we derived the viscosity as a function of compressive load and displacement under a constant crosshead speed. SPCT is effective in evaluating metallic glass viscosity regardless of glass forming capability. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.. |
| 26. |
森田 直志, 吉年 規治, 山田 類, 川崎 亮, 加圧含浸法および圧力付加液相焼結法によるFe系金属ガラス粉末固化成形, 日本金屬學會誌, 10.2320/jinstmet.76.653, 76, 12, 653-660, 2012.12, In a previous paper we reported that slightly pressurized liquid phase sintering permits to fabricate fully dense Fe-based metallic glass composites, that the phase content of dual phase structure can be controlled by pressure squeezing of the liquid phase, and that the fracture strength increases with an increase in solid phase volume fraction. Throughout the process the pore shape at the contact of the particles, and accordingly the shape of the liquid phase at the particle contacts, were found to keep a cusp-shaped morphology, which implies and guarantees a complete penetration of the molten alloy into the pore space. In the present study, a model experiment was employed using a mono-sized spherical Fe-based metallic glassy powder to show an advantage of the present process for the fully dense composite structure and for the control of the composition of the two phase structure. Two types of experiments were conducted; one is pressure infiltration in which hot pressed solid skeleton was impregnated with a molten alloy, and the other is a squeezing liquid phase sintering, in which a mixture of the solid metallic glass powder and a liquid-phase alloy powder was hot pressed to control the relative density and the content of the liquid phase by squeezing out the molten alloy. The squeezing liquid phase sintering was found to give fully dense compacts, compared to the solid sintering of the metallic glass powder, which gives the relative density of 97.5% at most. An incomplete penetration of molten alloy into the dense preform and also the formation of peripheral pores near the die wall in the case of the infiltration process are discussed.
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| 27. |
Ayako Miura, Wei Dong, Masahiro Fukue, Noriharu Yodoshi, Kenta Takagi, Akira Kawasaki, Preparation of Fe-based monodisperse spherical particles with fully glassy phase, Journal of Alloys and Compounds, 10.1016/j.jallcom.2011.02.044, 509, 18, 5581-5586, 2011.05, In this study, we prepared monodisperse spherical particles of a desired diameter using [(Fe0.5Co0.5)0.75B 0.2Si0.05]96Nb4 alloy; the particles were prepared by using an atomization process developed by us. The particles have perfect sphericity and narrow size distribution along with a homogeneous composition. The phase transitions of particles from the fully glassy phase to the crystalline phase via mixed phase structures occurred as the particle diameter was increased; the particles produced in the fully glassy phase in an argon atmosphere had a diameter of less than 300 μm. This allowed the estimation of the intrinsic critical cooling rate for the particles with a fully glassy phase, Rc:Rc varied in the range of 700-900 K/s and depended only on the initial temperature of the alloy melt. © 2011 Elsevier B.V. All rights reserved.. |
| 28. |
N. Yodoshi, R. Yamada, N. Morita, A. Kawasaki, R. Watanabe, Synthesis of Fe based metallic glass-Pd based metallic glass composite by slightly pressured liquid phase sintering, Materials Transactions, 10.2320/matertrans.M2010197, 51, 11, 2056-2062, 2010.11, To consolidate [(Fe0.5Co0.5)0.75Si 0.05B0.2]96Nb4 metallic glass powder to full density, a pressurized liquid phase sintering was employed, which was intended to promote densification by an enhanced wetting of a liquid phase with solid particles. Pd42.5Ni7.5P20Cu30 metallic glass powder, which has been reported to have a high glass forming ability and the lowest critical cooling rate of glass formation of 0.067 K/s, was chosen as a liquid phase component. The melting point of the Pd 42.5Ni7.5P20Cu30 metallic glass alloy of 763 K is lower than the glass transition temperature of the [(Fe 0.5Co0.5)0.75Si0.05B 0.2]96Nb4 metallic glass alloy of 808 K. However, the wettability of this alloy with the Pd42.5Ni 7.5P20Cu30 alloy was revealed to be poor. Therefore, sintering pressure was applied to the compacts to promote a viscous flow deformation of solid particles and also to enhance the intergranular permeation of the liquid phase. A specially designed micro-hot press was devised for the pressure-sintering experiment. A pseudo-wettability was observed during pressure-sintering, and the liquid phase was found to fill completely the intergranular space of the powder compact. The relative density of 64-95%, as well as the sintering structure, could be controlled by the punch displacement to squeeze out a part of the liquid phase from the compact. The compressive fracture strength of the obtained metallic glass composite was found to be as high as 2051 MPa, and the fracture was observed to be intragranular type, suggesting a good bonding in the particle-binding phase interlace. ©2010 The Japan Institute of Metals.. |
| 29. |
N. Yodoshi, R. Yamada, A. Kawasaki, R. Watanabe, Consolidation of [(Fe0.5Co0.5)0.75Si 0.05B0.2]96Nb4 metallic glassy powder by SPS method, Materials Transactions, 10.2320/matertrans.M2009093, 50, 9, 2264-2269, 2009.09, Metallic glasses have been reported to exhibit excellent properties, such as high strength, high corrosion resistance, high wear resistance, which result from their amorphous structure. Because of a drastic reduction in their viscosities in supercooled liquid region, metallic glasses have an excellent workability through viscous deformation for the production of various industrial parts. Recently, much attention has been paid to Fe-based metallic glasses because of their rich resources in addition to their excellent mechanical and magnetic properties. However, due to their poor glass-forming ability, the size of the Fe-based bulk metallic glass by conventional casting techniques is limited. In the present investigation, nearly fully densified disk-shaped compacts of [(Fe0.5Co0.5)0.75Sio 0.5Bo0.2.2]96Nb4 metallic glass were produced from a gas-atomized amorphous powder by spark plasma sintering (SPS). The processing temperature and the time that assure the supercooled liquid state of the compacts were determined from the Time-Temperature-Transformation (ttt) diagram that was constructed by isothermal differential scanning calorimetry. The mechanical properties of the consolidated samples were evaluated by compression test. Comparatively low values of the fracture stress. Young's modulus and yielding stress of SPSed sample compared to the casted samples were observed, which is discussed on the basis of the integrity of the interparticle bonding. © 2009 The Japan Institute of Metals.. |
| 30. |
三浦 彩子, 董 偉, 福江 正浩, 吉年 規治, 宮崎 孝道, 川崎 亮, パルス圧力付加オリフィス噴射法で作製したFe系金属ガラス合金単分散粒子の構造評価とガラス相形成のための臨界冷却速度, 日本金屬學會誌, 10.2320/jinstmet.73.636, 73, 8, 636-642, 2009.08, Mono-sized [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 alloy particles with desired particle size and high sphericity have been prepared by Pulsated Orifice Ejection Method (POEM). Each particle has uniform compositional distribution along with the same composition during processing. Phase transition of a particle from fully amorphous to amorphous/crystalline and then fully crystalline shows that the diameter of a single fully amorphous particle is less than 300 μm in Ar atmosphere and 700 μm in He atmosphere. The critical diameter of a fully amorphous phase particle shifts toward larger diameter with an increase in the initial melt temperature. The critical cooling rate to realize fully amorphous phase is estimated to be in the range of (700-900 K×s-1), which only depends on the initial melt temperature, irrespective of the atmospheres gases.
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| 31. |
吉年 規治, 森田 直志, 山田 類, 川崎 亮, 渡辺 龍三, 圧力付加液相焼結法によるFe系金属ガラス-Pd系金属ガラス複合材の作製, 日本金屬學會誌, 10.2320/jinstmet.73.643, 73, 8, 643-650, 2009.08, To consolidate [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glass powder to full density, a pressurized liquid phase sintering was employed, which was intended to promote densification by an enhanced wetting of a liquid phase with solid particles. Pd42.5Ni7.5P20Cu30 metallic glass powder, which has been reported to have a high glass forming ability and the lowest critical cooling rate of glass formation of 0.067 K/s, was chosen a liquid phase component. The melting point of the Pd42.5Ni7.5P20Cu30 metallic glass alloy of 763 K is lower than the glass transition temperature of the [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glass alloy of 808 K. However, the wettability of this alloy with the Pd42.5Ni7.5P20Cu30 alloy was revealed to be poor. Therefore, sintering pressure was applied to the compacts to promote a viscous flow deformation of solid particles and also to enhance the intergranular permeation of the liquid phase. A specially designed micro-hot press was devised for the pressure-sintering experiment. A pseudo wettability was observed during pressure-sintering, and the liquid phase was found to fill completely the intergranular space of the powder compact. The relative density of 64-95%, as well as the sintering structure, could be controlled by the punch displacement to squeeze out a part of the liquid phase from the compact. The compressive fracture strength of the obtained metallic glass composite was found to be as high as 2051 MPa, and the fracture was observed to be intragranular type, suggesting a good bonding in the particle-binding phase interface.
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| 32. |
山田 類, 吉年 規治, 川崎 亮, 渡辺 龍三, ＳＰＳ法によるＦｅ‐Ｃｏ系金属ガラス粉末の固化成形, 日本金属学会誌, 10.2320/jinstmet.73.299, 73, 4, 299-305, 2009.04, Metallic glasses have been reported to exhibit excellent properties such as high strength, high corrosion resistance, high wear resistance, resulting from their random structure. In addition, metallic glasses usually exhibit a drastic reduction in viscosity in the supercooled liquid region. Therefore, metallic glasses have excellent workability in this temperature range and it has already been reported that large size of bulk metallic glasses are successfully fabricated in several Zr-, Pd-based metallic glasses.
In recent years, Fe-based metallic glasses have been intensively studied because of their excellent mechanical performance, excellent magnetic properties and rich resources. However, due to their poor glass forming ability, the size of bulk metallic glasses is limited using a copper mold casting technique.
In the present study, [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 bulk metallic glasses are fabricated by spark plasma sintering (SPS) of amorphous powders which have been prepared by a gas atomization. To find optimum conditions in the SPS process, Time-Temperature-Transformation diagram (TTT diagram) is also constructed by isothermal differential scanning calorimetry. After consolidation of metallic glassy powders, mechanical properties of consolidated glassy specimens are measured by compressive tests.
As a result, the TTT diagram can be constructed and maximum incubation time can be predicted at any holding temperature. Using SPS method, large size and nearly 100% relative dense glassy compacts are obtained with a loading pressure of 75 MPa and 400 MPa, comprising full amorphous in the case within incubation time. Compressive tests indicate that mechanical properties of consolidated specimens are still low, and one of the reasons may be the formation of approximately 50 nanometer crystalline phases between each particle observed by Transmission Electron Microscope (TEM).
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| 33. |
三浦 彩子, 董 偉, 吉年 規治, 川崎 亮, 柳本 勝, パルス圧力付加オリフィス噴射法による単分散Fe系金属ガラス合金粒子の作製と評価, 粉体および粉末冶金, 10.2497/jjspm.56.9, 56, 1, 9-17, 2009.01, The mono-sized [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 metallic glass micro spherical particles with narrow size distribution and high sphericity have been successfully prepared by Pulsated Orifice Ejection Method (POEM). The desired size of particles can be formed by adjusting process parameters, such as the rod displacement, the time for reaching the pulse voltage from zero voltage, the applied pressure and so on. The glassy fraction determined by enthalpy released for the particles during continuous heating in DSC, based on 70.23 J·g−1 as the enthalpy released of a fully amorphous particle (as proved by X-ray diffraction), shows that the changes of phase in one particle from single amorphous phase to amorphous crystalline mixed phase and then overall crystalline occur within the range of 350 mm and 400 mm in diameters. The critical cooling rate for the occurrence of crystalline in single amorphous phase is estimated to be within the range of 700 and 800 K·sec−1, which is slightly lower than that measured by time-temperature transformation diagram of the bulk metallic alloy, and supposed to be affected by the initial temperature of the melt.. |
| 34. |
渡辺 龍三, 吉年 規治, 加藤 秀実, 川崎 亮, 金属ガラス粉末のホットプレス緻密化制御, 粉体および粉末冶金, 10.2497/jjspm.55.709, 55, 10, 709-714, 2008.10, The equations for the densification control by viscous flow in the hot pressing of metallic glass powders are derived and a criterion for the full densification thereof and an approach for the porosity control are proposed. The kinetic equations are derived on the basis of Arzt's hot pressing theory; in which the densification is modeled by the contraction of the Bolonoi cell of the random dense packing of spherical particles. The constitutive equation for the viscous flow is obtained from the hitherto proposed creep rate equation setting the rate exponent to be unity. The hypothetical constraint for the deformation due to the three grain edges formed in the later stage of densification is taken into account as a modification of the pressure term in the kinetic equations. The relative density is expressed as functions of hot pressing time and the ratio of the viscosity and the pressure. It is shown that the time required for full densification of metallic glass powders depends only on the viscosity/pressure ratio. The criterion for the full densification is expressed as a straight line on the time-viscosity/pressure ratio plane, which divides the area into full-dense and porous areas. The porosity control of the metallic glass powder compacts is also demonstrated as another practical application of the present theory. The results are discussed on the basis of the reported data.. |
| 35. |
吉年 規治, 三浦 彩子, 董 偉, 川崎 亮, パルス圧力付加オリフィス噴射法による球形単分散 Fe-Co 系金属ガラス粒子の作製, 日本金属学会誌, 10.2320/jinstmet.72.686, 72, 9, 686-692, 2008.09, Metallic glasses are potentially applied for accurate micro parts because of their good formability and transferability as well as high mechanical properties and excellent magnetic properties. So the raw materials that the volume is precisely controlled are needed for a highly accurate processing. In this study, mono-sized spherical particles of Fe-Co-based metallic glass were prepared by Pulsated Orifice Ejection Method (POEM) and the capabilities of their micro-forming process in the glass transition temperature were investigated.
Mono-sized spherical particles of Fe-Co-based metallic glass particles with 200-500 μm of diameter have been obtained by Pulsated Orifice Ejection Method (POEM). The XRD pattern of the particles shows only broad peaks without any crystalline peak. A bright field TEM image of the particles and the selected area diffraction patterns shows only halo patterns that indicate fully amorphous phase. DSC curve shows that supercooled liquid region was ΔT=48 K and a TTT curve can be constructed by isothermal DSC.
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| 36. |
Tokujiro Yamamoto, Noriharu Yodoshi, Teruo Bitoh, Akihiro Makino, Akihisa Inoue, Soft magnetic Fe-based metallic glasses prepared by fluxing and water-quenching, REVIEWS ON ADVANCED MATERIALS SCIENCE, 18, 2, 126-130, 2008.06, [(Fe(0.5)Co(0.5))(0.75)B(0.20)Si(0.05)](96)Nb(4) soft magnetic bulk metallic glasses were prepared by fluxing and water-quenching in a silica tube. Dimension of the bulk metallic glass specimens was up to 7.7 mm in diameter, which is about 1.5 times larger than those prepared by Cu mold-casting. The critical cooling rate of [(Fe(0.5)Co(0.5))(0.75)B(0.20)Si(0.05)](96)Nb(4) alloys with fluxing for forming a metallic glass phase was 150-170 K/s, which was considerably smaller than that without fluxing. Saturation magnetization was 1.13 T, and coercivity was lower than 20 A/m. Fluxing suppresses heterogeneous nucleation by isolating the nucleation sites from the molten alloys and improves their glass-forming ability.. |
| 37. |
Tokujiro Yamamoto, Noriharu Yodoshi, Hisamichi Kimura, Akihisa Inoue, Effects of additional elements on microstructures of Zr-based metallic glass ribbons, THERMEC 2006, PTS 1-5, 10.4028/www.scientific.net/MSF.539-543.2000, 539-543, 2000-+, 2007.03, Effects of Fe, Co and Al addition to Zr55Al10Ni5Cu30 and Zr70Cu30 metallic glass ribbons were studied. 20 at.% of Fe addition prevented Zr55Al10Ni5Cu30 molten alloys from being supercooled and resulted in nanocrystallization, while Zr55Al10Ni5Cu30 alloys containing 20 at.% Co could be quenched into a supercooled liquid region. Fe addition also degraded Zr70Cu30 metallic glass, while Al addition improved both glass phase stability and mechanical properties. Degradation of Zr-based metallic glass by Fe addition originates in the large negative enthalpy of mixing Fe with Cu.. |
