| Project/Area Number |
12450278
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | The University of Tokyo |
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Principal Investigator |
KANNO Motohiro The University of Tokyo, Graduate School of Engineering, Professor, 大学院・工学系研究科, 教授 (60011128)
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| Co-Investigator(Kenkyū-buntansha) |
KURAMOTO Shigeru The University of Tokyo, Graduate School of Engineering, Research Associate, 大学院・工学系研究科, 助手 (10292773)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥11,600,000 (Direct Cost: ¥11,600,000)
Fiscal Year 2001: ¥5,100,000 (Direct Cost: ¥5,100,000)
Fiscal Year 2000: ¥6,500,000 (Direct Cost: ¥6,500,000)
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| Keywords | high strength aluminum alloy / hydrogen embrittlement / duetrium / grain boundary fracture / slow strain rate tensite test / stress corrosion cracking / A7075 / coarse grained alloy / アルミニウム合金 / 質量分析計 |
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| Research Abstract |
Stress corrosion cracking (SCC) has been a serious problem in high strength aluminum alloys such as AI-Zn-Mg-Cu and Al-Cu-Mg alloys. Although it is believed that hydrogen embrittlement plays an important role in the SCC, few direct evidence has been revealed. This study was undertaken to demonstrate that SCC in a mild atmosphere obtain is a kind of hydrogen embrittlement. First, it was determined that a coarse grained Al-Zn-Mg-Cu alloy without grain refiners showed a quite low ductility with intergranular fracture when tested at a strain rate of 1.67x10-7/s, though the alloy showed a high ductility with transgranular fracture when tested at strain rates of 10-3〜10-4/s. Next, it was revealed that the alloy showed a quite high ductility in an environment with low humidity below 30 % when tested the lowest strain rate. This suggested that the embrittlement, I.e., quite low ductility is caused by hydrogen. In order to determine this presumption, the alloy specimen was strained about 1 % in an environment with heavy water vapor and subsequently tensile tested by use of a high vacuum tensile testing machine equipped with a quadrapole mass spectrometer. It was made clear that hydrogen is emitted from the specimen during deformation up to fracture. This means that the intergranular fracture as above is caused by hydrogen. The same embrittlement was also observed in commercially available alloys, A7075 anda7050 when tested at the lowest strain rates in an atmosphere with high humidity, and the embrittlement was caused by hydrogen by use of duetrium.
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