Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
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Volume 62, Issue 2
February
Displaying 1-6 of 6 articles from this issue
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Paper
Paper
  • Study on Cutting Properties and Threading of Porous Titanium
    Yuki SAKAMOTO, Hayato ABE
    2015 Volume 62 Issue 2 Pages 53-58
    Published: February 15, 2015
    Released on J-STAGE: March 31, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.53
    JOURNAL OPEN ACCESS
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    Biomaterials such as artificial bones, joints, and dental implants need to have the following properties, that is biocompatibility and mechanical properties similar to those of a metal. For these biomaterials, titanium and its alloys have been used in modern clinics. Especially, the medical concern with research of the porous titanium used as biomaterials has been growing for the last several years. However, very few attempts have been made at study on cutting properties of porous titanium. The aim of this study is to clarify the cutting properties of the porous titanium by vibration cutting. Surface roughness was stable when the amount of depth of cut is 0.1 mm. For threading processing of porous titanium, it was possible to process without deleting the titanium particle. The young’s modulus was 9.8～20.3 GPa, which is lower than the value for human cortical bone. This is can be adjusted in strength by annealing. We found that can be processed while retaining the characteristics of the porous titanium by vibration cutting.
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Special Issue: Important Subjects for Research and Application of Permanent Magnets
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  • Approach of Elements Strategy Initiative Center for Magnetic Materials toward Development of Critical-Element-Free High-Performance Permanent Magnets
    Satoshi HIROSAWA
    2015 Volume 62 Issue 2 Pages 61-66
    Published: February 15, 2015
    Released on J-STAGE: March 31, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.61
    JOURNAL OPEN ACCESS
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    In order to clarify and sort out entangled structure-related factors that determine the intrinsic coercivity of permanent magnet materials, both atomic-resolution microstructural analyses and description of the dynamics of magnetization associated with the microstructure are required. These are extremely challenging requirements that need further developments of analytical tools and computational techniques. Elements Strategy Initiative Center for Magnetic Materials (ESICMM) sets platforms for these two areas of investigations where researchers from various backgrounds interact with each other and develop an integrated description of structure-coercivity phenomena as a multi-physics phenomenon. This article briefly describes the ESICMM activities in these platforms and a few examples of its current achievements in the subfields of Dy–free Nd–Fe–B and new materials exploration.
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  • Magnetic Domain Observation of Nd–Fe–B Sintered Magnet at Elevated Temperature
    Masaaki TAKEZAWA, Hirofumi OGIMOTO, Yuji MORIMOTO
    2015 Volume 62 Issue 2 Pages 67-71
    Published: February 15, 2015
    Released on J-STAGE: March 31, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.67
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    Magnetization reversal and its propagation in sintered Nd–Fe–B magnets were clearly observed at elevated temperature up to 150 ˚C using a Kerr microscope, image processing, and photo editing. Simultaneous magnetization reversal in several grains along the easy axis direction occurred at elevated temperature, and the extent of simultaneous magnetization reversal increased with temperature. This indicates that reduction in the coercivity of Nd–Fe–B sintered magnets at elevated temperatures is attributable to decrease in anisotropy and insufficient pinning of domain walls at grain boundaries.
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Paper
  • Propagation mechanism of magnetized and demagnetized regions in Nd–Fe–B sintered magnet
    Kurima KOBAYASHI, Kimiko URUSHIBATA
    2015 Volume 62 Issue 2 Pages 72-76
    Published: February 15, 2015
    Released on J-STAGE: March 31, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.72
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    Nd–Fe–B sintered magnet is one of the most interesting materials especially for applications in EV and HV motor parts. This study deeply concerns to coercivity of the magnets, and that also relates to the serious Dy resource problem being watched recently. We investigated the magnetization and demagnetization mechanisms in commercial NEOMAX–48 magnet using EBSD, MFM, and Cs–TEM. The orientation of crystal grains mainly on c–plane (EBSD), domain structures of magnetized and demagnetized regions including the intermediate states (MFM), and the chemical composition and crystal and micro-structures including the thickness (Cs–TEM), all at the same position in the same magnet sample were studied. The propagation of magnetized and demagnetized regions surrounding the miss-orientated small number of grains was observed. The grain boundaries (GB) between (A) magnetized-magnetized grains and between (B) magnetized-demagnetized grains are similar thickness of 1.2−2.0 nm and similar amorphous structure including about 30 % of Fe, except the different oxygen contents of 10 % (A) and 40 % (B). As conclusion, the magnetic states of surface grains are mainly governed by the magnetic flux from the inside grains, and the GBs ((A) and (B)) have no specific different characteristics as chemical composition and crystal structure.
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