2005 Fiscal Year Final Research Report Summary
Improvement of resistance to environment-assisted cracking of high strength aluminum alloys for the next generation
| Project/Area Number |
16560612
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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 | Kansai University (2005)
Osaka University (2004) |
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Principal Investigator |
HARUNA Takumi Kansai University, Faculty of Engineering, Lecturer, 工学部, 専任講師 (70243186)
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| Co-Investigator(Kenkyū-buntansha) |
FUJIMOTO Shinji Osaka University, Department of Materials Science and Processing, Professor, 大学院・工学研究科, 教授 (70199371)
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| Project Period (FY) |
2004 – 2005
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| Keywords | environment-assisted cracking / aluminum alloy / chloride solution / electrochemical potential / pH / breakdown of passive film / absorption of hydrogen |
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| Research Abstract |
We have investigated environment-assisted cracking (EAC) and hydrogen absorption of Al-Mg-Mn (5083) alloys in 0.1 M chloride solutions of pHs 1,3, and 7 at 25℃. We employed a slow strain rate EAC testing apparatus and a thermal desorption gas analyzer (TDA).
The following results were obtained from the EAC tests : (1)Under a potential over a film-breakdown potential of about -740 mV_<Ag/AgCl>, a fracture strain in the solution of any pH was smaller than that obtained in the inert (air) condition. In addition, the fracture strain decreased with lowering pH. (2)Under a cathodic potential of -1000 mV_<Ag/AgCl>, the fracture strain obtained in the solution of any pH was almost the same as that in the inert condition. (3)At -1500 mV_<Ag/AgCl>, the fracture strain in the solution of pH 1 was almost the same as, and those in the solutions of pH 3 and 7 were smaller than that in the inert condition.
The following results were obtained from the TDA tests : (4)Under a potential over the film-breakdown potential, remarkable hydrogen absorption was not detected in the solution of any pH. (5)In the solution of pH 1, remarkable hydrogen absorption was not detected in the cathodic potential region to -1500 mV_<Ag/AgCl>. Besides, the amount of hydrogen absorption in the solutions of pHs 3 and 7 slightly increased with lowering potential. Further, the amount of hydrogen absorption increased with an increase in pH.
In comparison with Al-Mg-Si (6061) alloy investigated last year, it is found that this Al-Mg-Mn alloy is hard to absorb hydrogen in any potential condition, and slight hydrogen absorption may relate to decrease in fracture strain. Finally, it is suggested in the whole research that both the materials avoid strength-degradation related to environment when the materials are used as their electrochemical potentials are maintained around -1000 mV_<Ag/AgCl>
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