| Project/Area Number |
18560689
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Material processing/treatments
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
SAKAI Taku The University of Electro-Communications, Faculty of EC, Professor (40017364)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,840,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥240,000)
Fiscal Year 2007: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2006: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Keywords | Severe plastic deformation / Multi-directional forging / Fine-grained structure / Microshear band / Kink band / Continuous dynamic recrystallization / Grain fragmentation / Anneasling / 温間,冷間加工 / ミクロシアバンド / 焼なまし / 連続再結晶 |
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| Research Abstract |
The process and mechanisms of fine-grained structure formation during severe large deformation was studied in multi-Directional forging (MDF) and a single pass compression at low and high temperatures by using Cu and Al, Mg and Fe alloys. The relationships between deformation characteristics and evolution process of microstructures were systematically analyzed, and the main results obtained were summarized as follows.
1. Several kinds of deformation bands such as microshear and kink bands are generated in grain interiors in above a critical strain. The density and the misorientations of their boundaries increase with straining, leading to fragmentation of original grain interiors and finally formation of new fine-grains. The process of such strain-induced grain formation is concluded to be controlled by in-situ or continuous dynamic recrystallization.
2. Deformation bands are developed in various directions in three-dimensional space during MDF, leading to formation of fine-grained structures in large strain. This means that MDF is one of effective methods for fine-grained structure formation.
3. The process of new fine grain formation in a wide temperature interval can be classified into the three stages : (1) formation of conventional dislocation substructures accompanied with embryos of deformation bands (DBs) in stage 1 (ε<2) ; (2) development of large scale DBs followed by grain fragmentation, leading to new grain formation along DBs at moderate strains in stage 2 (2<ε<4) ; (3) development of new grained structures at high strains in stage 3 (ε>4).
4. Annealing of such strain-induced grain structure can not be controlled by conventional discontinuous recrystallization including nucleation and growth of new grains, but also by in-situ or continuous static recrystallization, in which grain growth takes place accompanied with recovery.
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