| Co-Investigator(Kenkyū-buntansha) |
YOSHIMURA Hirofumi Fnkuyama University, Department of Eng., Professor, 工学部, 教授 (70279082)
SUGIMOTO Satoshi Tohoku University, Graduate School of Eng., Assoc. Professor, 大学院・工学研究科, 助教授 (10171175)
FUKAI Yuh Chuou University, Department of Physics, Professor, 理工学部, 教授 (80055136)
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| Research Abstract |
The pressure dependence of structural changes of C15 Laves phase TbFe_2 heated in a hydrogen atmosphere was investigated using PDSC, XRD, DSC and a hydrogen analyzer. Hydrogen absorption in the crystalline state, hydrogen-induced amorphization (HIA), precipitation of TbH_2 and decomposition of the remaining amorphous alloy into ヲチ-Fe and TbH_2 occurred exothermally with increasing temperature above 0.5 MPa H_2, independent of the heating rate. HIA and precipitation of TbH_2 occurred simultaneously in 0.2 MPa H_2 (O.33 K/s) and in 0.1 MPa H_2 (0.17 K/s). On the contrary, hydrogen absorbed crystalline c-TbFe_2H_<3.5> decomposed directly into ヲチ-Fe and TbH_2 in O.1 MPa H_2 (O.33 K/s). That is, no amorphous phase was formed at the lower hydrogen pressure and at a high heating rate. The reason why HIA occurs above the critical hydrogen pressure and below the critical heating rate was discussed on the basis of the hydrogen content absorbed in the crystalline state of The Fe _2. 2) Formation
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of hydrogen-induced superabundant vacancies has been studied in Cr-H, Mn-H, Ni-H and Nb-H alloys and its energetics and structure dependence has been elucidated. 3) The relationship between hydrogen pressure and temperature (P-Tcurve) in the HDDR treatment of the Sm_2Fe_<l7> compound was investigated. The P-T curve suggested that the HDDR condition of the Sm_2Fe_<l7> compound was more sensitive to temperature than that of the Nd_2Fe_<l4>B compound. In addition, for clarifying the mechanism of anisotropic inducement during the HDDR process in the Nd-Fe-B compound, the crystal orientation relationship between the parent Nd_2Fe_<l4>B phase and the disproportionated mixture was investigated. It can be concluded that retaining the crystallographic orientation relationship such as <111>ヲチ-Fe and <111>NdH_2// <001>Nd_2Fe_<l4>B, (110)ヲチ-Fe and (110)NdH_2//(lOO)Nd_2Fe_<l4>B during HDDR treatment is important for the inducement of anisotropy. 4) It has been found that the tensile specimen of ultra-fine grained Ti-6Al-4V alloy elongates until the diameter of the tip of the broken specimen narrowed to the size of a single crystal. The implant (dental part) was produced using the ultra-fine grained material without crack on the surface by the superplastic forming process. These materials may be applicable as biomaterials in medical industries. Less
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