The Effects of Grain-Boundary Inclusions on High-Temperature Fracture of Metals
| Project/Area Number |
60420046
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属材料(含表面処理・腐食防食)
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| Research Institution | Yokohama National University (1986)
Tokyo Institute of Technology (1985) |
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Principal Investigator |
TANAKA Ryohei Yokohama National University, 工学部, 教授 (80016188)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIHARA Michiko Yokohama National University, 工学部, 助手 (70111705)
HORIE Shiro Tokyo Institute of Technology, 大学院総合理工学研究科, 助手 (90114892)
KATO Masaharu Tokyo Institute of Technology, 大学院総合理工学研究科, 助教授 (50161120)
MORI Tsutomu Tokyo Institute of Technology, 大学院総合理工学研究科, 教授 (40016259)
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| Project Period (FY) |
1985 – 1986
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| Project Status |
Completed (Fiscal Year 1986)
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| Budget Amount *help |
¥15,500,000 (Direct Cost: ¥15,500,000)
Fiscal Year 1986: ¥6,000,000 (Direct Cost: ¥6,000,000)
Fiscal Year 1985: ¥9,500,000 (Direct Cost: ¥9,500,000)
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| Keywords | High-temperature fracture / Dispersion-hardened alloy / Grain-boundary sliding / Intergranular fracture / Void growth / Intermediate-temperature Embrittlement / Diffusion-controlled deformation / 引張試験 / 高温変形 / 結晶粒界介在物 / 動的再結晶 |
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| Research Abstract |
This research project is aimed to examine the effects of grain-boundary inclusions on high-temperature deformation and fracture behavior of metals.
For the experimental part of the project, copper polycrystals with dispersed Ge <O_2> particles on grain boundaries were used as a model system and high-temperature deformation and fracture characteristics were investigated in detail.
As temperature increases from room temperature to 900 K, ductility first decreases with a minimum at around 600 K and then increases again. The degree of such intermediate-temperature embrittlement is sensitive to both strain rate and the size of the Ge <O_2> particles at grain boundaries. Microscopic observation of fracture surfaces has revealed that the initial decrease of ductility occurs concurrently with the occurrence of grain-boundary sliding (GBS) and that the recovery of ductility at higher temperatures is due to the initiation of extensive recrystallization.
From the above experimental results, it is concluded that at the intermediate temperature range, local stresses which concentrate near the Ge <O_2> particles at the sliding grain boundary induce the formation of voids which eventually grow and coalesce to cause intergranular fracture. At higher temperatures, the stress concentration is relaxed by the recrystallization, resulting in the recovery of ductility.
As the theoretical part of the project, diffusion-controlled GBS and the growth of voids on grain boundaries were examined by considering the change in the overall mechanical (Gibbs) free energy of a system containing a grain boundary or a void. It is found that these problems can be treated in a simple unified manner without knowing local stress fields and that the GBS rate and the void growth rate can be derived very easily. The knowledge derived from this theoretical study is considered to be very useful in understanding various aspects of high-temperature deformation and fracture behavior.
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Report
(2 results)
Research Products
(11 results)
