2005 Fiscal Year Final Research Report Summary
A study on the clarification of formation mechanism, environmental embrittlement and fatigue behavior of nanocrystals
| Project/Area Number |
16560617
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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 |
Structural/Functional materials
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| Research Institution | Doshisha University |
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Principal Investigator |
MIMAKI Takuro Doshisha Univ., Faculty of Engg., Professor, 工学部, 教授 (20066244)
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| Co-Investigator(Kenkyū-buntansha) |
MIYAMOTO Hiroyuki Doshisha Univ., Faculty of Engg., Asso.Professor, 工学部, 助教授 (10298698)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Ultra-fine grain / ECAP technique / Single crystal / Severe deformation / Shear band / SCC sensitivity / Impact strength / Deformation twin |
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| Research Abstract |
Ultra-fine grain copper samples were produced by ECAP (Equal-Channel angular pressing) technique using well-oriented copper single crystals having, <001>, <011>. and <111> axis direction. The investigations were performed during the formation of ultra-fine crystals by severe plastic deformation. The fining process in the formation of ultra-fine grains was divided to the following three groups ; (1)Shear bands were formed parallel to the shear direction of the initial single crystal inserted, (2)Deformation bans were deformed to the insert direction of the single crystal and (3)Both bands described above were not formed. The dislocation structure of the shear band were formed by very dense and tuft-like microbands and the mirror relationship was observed between the microband and the matrix. From a detailed TEM observation, the deformation twins with about 200 nm width were observed. The formation mechanism of the deformation twin was clarified as the "Pole mechanisms".
From the investig
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ations on behavior of crack initiation and propagation, it was clarified that crack initiation and propagation mode were intergranular type and tendency of the relation between stress intensity factor and crack propagation rate was divided to two regions as same as the practical use materials. The SCC sensitivity was extremely decrease by the crystal fining. The cracks in specimen produced from single crystals were branched off to many direction, snaked and it takes much time to propagate, compared with the specimen produced from polycrystals.
Impact test was performed using ultra-fine grained aluminum. From the results, the impact strength of the ultra-fine grained aluminum was 1.6〜2.3 times higher than the practical use aluminum. Under both room and very low temperature, 77K, the impact strength was showed the very clear strain rate dependence, and the impact strength was increased with strain rate increasing.
These results described above were already published in Phil.Mag.Letters, Scripta Materialia, Mater. Sci. & Engg. and etc. Less
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Research Products
(14 results)
