1995 Fiscal Year Final Research Report Summary
HREM Study of high temperature metals and ceramics
| Project/Area Number |
06044169
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
NEMOTO Minoru Faculty of Engineering, Kyushu University, Professor, 工学部, 教授 (90005265)
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| Co-Investigator(Kenkyū-buntansha) |
MCCARTNEY Martha r Center for High Resolution elctron Microscopy, ASU., 高分解能電子顕微鏡センター, 教授
SMITH David j Center for High Resolution elctron Microscopy, ASU., 高分解能電子顕微鏡センター, 教授
MATSUMURA Sho Faculty of Engineering, Kyushu University, 工学部, 助教授 (60150520)
TOMOKIYO Yoshitsugu Faculty of Engineering, Kyushu University, 工学部, 助教授 (40037891)
HORITA Zenji Faculty of Engineering, Kyushu University, 工学部, 助教授 (20173643)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Intermetallics / Heat Resistance Alloys / High Regalution Electron microscopy / Analytical electron microscopy / Canugent-Beam Elecron Diffraction / Precipitation hardening / High-tenpeatare creep deformation / Site Occuponny / Submicrometer-grained |
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| Research Abstract |
Intermetallics and ceramics, which are attractive as heat-resistance meterials, were examined by high-resolution electron microscopy (HREM), analytical lectron microscopy (AEM) and eneg-filtered electron microscopy (EFEM).The internal structures of the intermetallics and ceramics were controlled by various heat treatments including straining. The results obtained in this stuy are summarized as folows.
(1) It was possible to obtaine a fine dispersion of Ni_2AlTi and Ni_2AlHf precipitate particles in NiAl intermetallics.There was a significant improvement of the creep strength (about 10 orders of magnitude) when compared with the NiAl without the particles. HREM revealed that the interaction between dislocations and particles is an attractive type. The threshold stress for the deformation was found to be about 270 MPa.
(2) Addition of Fe to NiAl intermetallics was effective at higher stresses to ncrease the creep strength. HREM showed that subboundaries were formed in the creep deformation of NiAl with Fe, whereas no subboundaries were observed in the deformation of NiAl without Fe. It was oncluded thet the creep deformation of NiAl with Fe is the alloy type and that of NiAl without Fe is the metal type.
(3) EFEM showed that addition of Mn to TiAl reduced the strength of covalent bonding between Ti and Al and lowered the c/a to activate many slip system. It was then suggested that the ductility of TiAl can be improved by an addition of Mn.
(4) AEM showed that alloying elements of Mn and Fe, which are effetive to improve ductility of Ni_3Al, were located at both the Al and Ni sites in almost an equal magnitude. In this experiment, delocalization effect were corrected using disordered phases.
(5) HREM showed that the grain bondaries of submicrometer-grained Al-Mg alloys produced by intense plastic straining tehnique contained a regular or irregular arrangement of facets and steps and thus were in a high energy non-equilibrium state.
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