2005 Fiscal Year Final Research Report Summary
Basic research on safety of high pressure hydrogen vessels made of aluminum alloys for fuel cell vehicles
| Project/Area Number |
16360344
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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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| Project Period (FY) |
2004 – 2005
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| Keywords | Al-Mg-Si Alloy / high humidity environment / slow strain rate testing / hydrogen embrittlement / Si excess alloy / Si-rich Precipitates / exfoliation of interface / liner material |
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| Research Abstract |
Research has been made on susceptibility to hydrogen embrittlement of Al-Mg-Si base alloys which will be used for high pressure hydrogen vessels of future fuel cell vehicles : the pressure will be increased up to 700Mpa or 1000Mpa in a near future. At first, the effect of alloy composition and aging condition on the susceptibility was examined on Al-Mg-Si alloys having rather low solute contents compared to those in A6061 alloy by means of a slow stain rate testing (SSRT) under high relative humidity. It was made clear that an alloy having excess silicon showed the susceptibility : ductility obtained by testing at an initial strain rate of 10^<-7>/s was lower than that at a rate of 10^<-4>/s. In contrast to this, an alloy having a composition of Mg/Si=2 and additive copper was immune to hydrogen embrittlement with the inverse result. The embrittlement was revealed to be related to exfoliation of the interface between the matrix and silicon-rich precipitates formed on grain boundaries.
Next, the susceptibility was also examined on three alloys, i.e., A6066, A6013 and A6070 alloys, which had been developed for body sheet materials of automobiles because of their higher strength than that of A6061 alloy being used for the vessel at 35Mpa. It was shown that these alloys were immune to hydrogen embrittlement : ductility was higher when tested at 10^<-7>/s than at 10^<-4>/s. The reason may be partly attributed to hydrogen trapping effect caused by densely distributed precipitates in the matrix and partly to the refinement of the silicon-rich precipitates formed on grain boundaries. The effect of copper addition was revealed to the refinement of silicon-rich precipitates on the grain boundary. As a result, these alloys were regarded to be promising candidates for the future liner materials of the hydrogen vessels.
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Research Products
(6 results)
