1994 Fiscal Year Final Research Report Summary
Clarification and Prevention of the Embrittlement in Metallic Materials
| Project/Area Number |
05452285
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Structural/Functional materials
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| Research Institution | The University of Tokyo, Faculty of Engineering |
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Principal Investigator |
KANNO Motohiro The University of Tokyo, Faculty of Engineering, Department of Materials Science, Professor, 工学部, 教授 (60011128)
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| Co-Investigator(Kenkyū-buntansha) |
OKADA Hiroshi The University of Tokyo, Graduate School, Division of Engineering, Department of, 大学院・工学系研究科・博士課程, 大学院生 日本学術振
ITOH Goroh The University of Tokyo, Faculty of Engineering, Department of Materials Science, 工学部, 助手 (80158758)
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| Project Period (FY) |
1993 – 1994
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| Keywords | fracture of metallic materials / intergranular fracture / trace impurity / mass spectrometer / ultra high vacuum testing machine for materials / hudrogen partial pressure / impurity sodium / impurity hydrogen |
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| Research Abstract |
The effect of trace impurities on the embrittlement of an A1-4%Cu alloy caused by intergranular fracture was studied in the last fiscal year. The GD-MS (glow discharge mass spectrometer) suggested that intergranular fracture of peak aged specimens was due to trace impurity of sodium below l mass ppm. It was concluded that the intergranular fracture was closely related to impurity sodium, since the addition of sodium up to 1 mass ppm to the alloy, which was made from 99.999% purity aluminum and 99.996% copper, increased intergranular fracture.
In the current fiscal year, the research was made on the effect of impurity hydrogen on the fracture of various metallic materials. It has been shown that hydrogen is evolved from tensile test specimens of pure copper, pure titanium and pure aluminum and their alloys at the time of fracture by use of a newly developed tensile testing machine which is equipped with a ultra high vacuum specimen chamber and a quadrupole mass spectrometer. Hydrogen may
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be evolved from specimens during deformation prior to fracture, but it was impossible to detect hydrogen during deformation because of high partial pressure of hydrogen in the specimen chamber. Therefore, an ion pump was added to the newly developed machine to decrease the partial prssure of hydrogen and as a result an ultra high vacuum of 10^<-9>Pa was attained. However, the detection of hydrogen during deformation was still difficult because of the evolution of gasses from the quadrupole mass spectrometer being used. Thus, the present mass spectrometer was replaced by a new quadrupole mass spectrometer which was designed to work well under ultra high vacuum. The partial pressure of hydrogen during testing was lowered for one order and the hydrogen was successfully detected even during deformation.
In the course of testing, it was found that methane was evolved together with hydrogen at the time of fracture and detection limit is much lower in the case of methane because of its low partial pressure in the specimen chamber. In addition, hydrogen is evolved from intergranular fracture surface of a specimen of iridium which is expected to become a new material for high temperature use. This suggests that hydrogen is also related to the intergranular fracture of iridium specimens. The decrease in the amount of impurity hydrogen may be needed to increase the ductility of iridium. Less
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Research Products
(6 results)
