1990 Fiscal Year Final Research Report Summary
"Creep Test of New Materials at High Temperatures in a HVEM"
| Project/Area Number |
63850140
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| Research Category |
Grant-in-Aid for Developmental Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Research Field |
Physical properties of metals
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
SATO Akikazu Tokyo Institute of Technology The Graduate School at Department of Materials Science and Engineering Professor, 大学院・総合理工学研究科, 教授 (20089824)
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| Co-Investigator(Kenkyū-buntansha) |
MORI Tsutomu Tokyo Institute of Technology The Graduate School at Department of Materials Sci, 大学院総合理工学研究科, 教授 (40016259)
KATO Masaharu Tokyo Institute of Technology The Graduate School at Department of Materials Sci, 大学院総合理工学研究科, 助教授 (50161120)
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| Project Period (FY) |
1988 – 1990
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| Keywords | In-situ observation / Refractory alloys / High temperature / deformation / Shape memory alloy / High voltage electron / Microscope |
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| Research Abstract |
A side entry type creep machine was designed for the in-situ high temperature testing in a high voltage electron microscope. A miniature tensile specimen was heated by a direct current and deformed under a constant load applied by a soft spring. Use of the soft spring enabled one to control the load and to observe the dislocation motion easily at any high temperatures accompanying thermal expansion. The results obtained in the present study are summarized as follows.
1) The studies of deformation of proton irradiated Mo and Fe-Cr-Ni single crystals were made in cooperation with the Nuclear Materials Division at the National Research Institute for Metals. Channeling deformation and dislocation reactions involved in the elimination of faulted loops in the proton irradiated Fe-Cr-Ni (fcc) and perfect loops in the proton irradiated Mo (bcc) are examined in detail to identify the responsible mechanisms causing the inhomogeneous deformation in irradiated materials.
2) Operation of a pole mechanism was confirmed in gamma->epsilon martensitic transformation in a Fe-Mn-Si shape memory alloy. It was the key in recording the dynamic process to slow down the dislocation multiplication by adjusting the deformation temperature near T_O so that the chemical driving force for the gamma->epsilon transformation is minimized. The in-situ observation of epsilon->gamma reverse transformation was also made successfully by applying a small load during heating as to prevent bending due to thermal expansion. It was revealed that the reverse transformation takes place at different temperatures in the range 373-673K depending on the complexity at the epsilon-epsilon intersection.
3) An intermetalic compound Ni_3Al was deformed at various temperatures in a HVEM. It was found that imoblization of dislocation segments by cross slip from {111} to {100} plane causes increase of a flow stress and hence leading to the high temperature strengthening.
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