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Ozaki Yukiko Last modified date:2019.06.18

Professor / Department of Materials Science and Engineering,Faculty of Engineering
Department of Materials Science and Engineering
Faculty of Engineering


Graduate School
Undergraduate School
Other Organization


E-Mail
Homepage
(under construction)
Phone
092-802-2941
Academic Degree
Dr.Sci.
Field of Specialization
Powder Metallurgy, Magnetic Materials
Research
Research Interests
  • 1) Analysis of intrinsic fracture mechanism of porous materials by X-ray CT observation
    2) Creating heterogeneous sintered steel with reguard to both strength and toughness.
    3) Thermodynamic analysis of alpha- /beta- relaxation process observed in metallic glasses, and proposal of low energy deformation process by promoting these atomic relaxations.
    4) Analysis of orgin of coercivity in powder iron magnetic core.
    keyword : metallic glass, sintered materials, powder magnetic core
    2016.09~2023.03.
Academic Activities
Papers
1. Y. Ozaki, Y. Mugita, M. Aramaki, S. Ooue, O. Furukimi, F.Jiang, T.Tsuji, A. Takeuchi, M. Uesugi and K. Ashizuka, Four-dimensional (4D) Observation of Ductile Fracture in Sintered Iron using Synchrotron X-ray Laminography., Powder Metallurgy, 10.1080/00325899.2019.1585032, 62, 2, 145-154, 2019.02, Synchrotron X-ray laminography was used to reveal the time evolution of the three-dimensional (3D) morphology of micropores in sintered iron during a tensile test. 3D snapshots showed networked open pores growing wider than 20 µm along the tensile direction, resulting in internal necking of the specimen. Finally, these pores initiated cracks perpendicular to the tensile direction by coalescing with surrounding preexisting microvoids or secondary-generated voids immediately before fracture. Topological analysis of the barycentric positions of these microvoids showed that they formed two-dimensional networks within a ~20 µm-radius area. This indicates that microvoid coalescence could occur on shear planes formed close to the enlarged open pores or between closed pores by strain accumulation and play an important role in crack initiation..
2. Y. Ozaki, Y. Mugita, M. Aramaki, S. Ooue, O. Furukimi, F.Jiang, T.Tsuji, A. Takeuchi, M. Uesugi and K. Ashizuka, Four-dimensional (4D) Observation of Ductile Fracture in Sintered Iron using Synchrotron X-ray Laminography., Proc. EuriPM2018, 2018.10, Synchrotron X-ray laminography was used to reveal the time evolution of the three-dimensional (3D) morphology of micropores in sintered iron during a tensile test. 3D snapshots showed networked open pores growing wider than 20 µm along the tensile direction, resulting in internal necking of the specimen. Finally, these pores initiated cracks perpendicular to the tensile direction by coalescing with surrounding preexisting microvoids or secondary-generated voids immediately before fracture. Topological analysis of the barycentric positions of these microvoids showed that they formed two-dimensional networks within a ~20 µm-radius area. This indicates that microvoid coalescence could occur on shear planes formed close to the enlarged open pores or between closed pores by strain accumulation and play an important role in crack initiation..
3. Takashita Takuya, Nakamura Naomichi, Ozaki Yukiko, Influence of Particle Shape on Microstructure and Magnetic Properties of Iron Powder Cores, Material Transactions, 57, 11, in press, 2016.09, The coercive force of an iron powder core decreases with an increase in the circularity of raw iron powder. Microstructural observation reveals that the crystal grain size of the iron powder core is reduced through recrystallization during the stress relief annealing after the powder compaction. An analysis of the work hardening behavior through the compaction process shows that a rounder particle shape leads to a smaller particle deformation, resulting in a reduction of the crystal grain refinement through recrystallization. A grain boundary pinning model well describes the reduction of coercive force with the increase in the eventual grain size..
4. Unami Shigeru, Uenosono Satoshi, Ozaki Yukiko, Fatigue strength of sintered and carburized compacts made of molybdenum hybrid-alloyed steel powder., Adv. Powder Merall. Part. Mater. , 10, 56-65, 2016.07.
5. Ozaki Yukiko, Takamuya Tsuguyuki, Ono Tomoshige, Mechanisms of stick-slip vibration during warm compaction of iron powder., Adv. Powder Merall. Part. Mater., 01.10-01.18, 2015.09.
6. Ono Tomoshige, Sato Takanori, Ozaki Yukiko, Approach for reducing variation in weight of PM green parts in mass productive pressing line by addition of nanoparticle to raw material powder., Adv. Powder Merall. Part. Mater., 21, 03.26-03.33, 2014.09.
7. Maetani Toshio, Unami Shigeru, Ozaki Yukiko, Effect of a Newly Developed Machinability Aid on Machinability of Sintered Steels. , Powder Metallurgy World Congress & Exhibition. Yokohama, Japan (CD-ROM). 2012,, P-T7-74., 2012.12.
8. Ozaki Yukiko, Uenosono Satoshi, Tagami N, Noda Reiji, Horio Masayuki, Kuwagi Kenji, Experimental and numerical investigations of the die filling of iron powders., Adv. Powder Merall. Part. Mater., 1, 3.35-3.46, 2006.09.
9. Ozaki Yukiko, Uenosono Satoshi, Ogura Kuniaki, An analysis of the compaction behaviors of iron powders during warm compaction., Adv. Powder Merall. Part. Mater., 1, 2.109-2.155, 1999.09.
Presentations
1. Yukiko Ozakia, Yasutaka Mugita, Masatoshi Aramaki, Satoshi Ooue, Kosuke Ashizukab, Akihisa Takeuchi, Masayuki Uesugi and Osamu Furukimia, Four-dimensional (4D) Observation of Ductile Fracture in Sintered Iron using Synchrotron X-ray Laminography , EuroPM 2018 Conference and Exhibitions, Birbao, 2018.10, Using synchrotron X-ray laminography, time evolution of the 3-dimensional (3D) morphology of micropores in sintered iron during a tensile test is revealed for the first time. The 3D snapshots showed networked open pores growing wider than 20 m of width along the tensile direction, resulting in the internal necking of the specimen. Finally, the enlarged-open pores initiated cracks perpendicular to tensile direction by coalescing with surrounding micro-voids pre-existent or secondary generated just before fracture. Therefore, by the topological analysis of their barycentric positions, these micro-voids formed 2-demensional networks in the area within about 20 m round. It indicates that coalescence of micro-voids could occur on share planes formed close to the enlarged-open pore by strain accumulation and play an important role in the crack-initiation..
2. Muhammad Kozin, Naoya Yamada, Masatoshi Aramaki, Yukiko Ozaki ,Osamu Furukimi, Wear Resistance of Sintered Pure Iron Treated by Acetylene Gas Carburizing Process, JSPM International Conference on Powder and Powder Metallurgy 2017 ~60th Anniversary, 2017.11, The wear resistance without lubrication of sintered pure iron treated by vacuum carburizing process was investigated. The sliding test results revealed that the wear volume of the specimen treated by the C2H2 gas carburizing decreased about 75% in comparison with the one without the heat treatment. The wear profile observation by Laser microscope of friction surface for the specimen treated by the C2H2 gas carburizing was seemed to be a relatively shallow. In contrast, in specimen without the heat treatment, the relatively deep valley was observed. In addition, a micro-ploughing track and relatively deep scar parallel to the sliding direction which is the characteristic of abrasive wear were observed in the specimen without the heat treatment. Nano-indentation hardness at near the surface of the specimen treated the C2H2 gas carburizing increased from value of HIT amounted to 1751 N/mm2 before heat treatment to 7699 N/mm2 after the heat treatment. The EBSD analysis results showed that the carburized layer consisted of a tempered martensitic phase and a small amount of a retained austenite phase. From these results, it can be concluded that the enhanced wear resistance of the C2H2 gas carburizing specimen is attributed to the increase in the hardness due to the presence of the martensitic phase layer at the surface. This layer is considered to inhibit the surface degradation due to micro-ploughing or exfoliation resulting in a high wear rate..
3. Takashita,Takuya, Nakmaura, Naomichi, Ozaki, Yukiko, Influence of Microstructure on Hysteresis Loss of Pure Iron Powder Core., World PM2016 Congress & Exhib, 2016.10, [URL].
4. Maetani,Toshio, Unami,Shigeru, Ozaki,Yukiko, Yamanichi,Y., Properties of sintered compacts and heat-treated compacts after sintering made of low Cr prealloyed steel powder. , Euro PM 2013, 2013.09.
5. Maetani,Toshio, Unimi,Shigeru, Ozaki, Yukiko, Effect of a Newly Developed Machinability Aid on Machinability of Sintered Steels., Powder Metallurgy World Congress & Exhibition., 2012.10.
6. Shimotomai,M., Fukuda,Y., Fujita,A., Ozaki,Y., Corrosion-Resistant Nd-TM-B Magnet., INTERMAG '90, 1990.09.
7. Takajyo,S., Ozaki,Y., Frequency dependence of the permeability and iron loss of iron powder dust cores for high frequency applications. Power Convers., Motion HFPC Conf. 1998, 1998.09.
Membership in Academic Society
  • Europian Powder Metallurgy Association (EPMA)
Educational
Other Educational Activities
  • 2016.09.