Martensitic Transformation and its Composition Dependence in Ti-Ni-Cu Shape Memory Alloys
| Project/Area Number |
16560584
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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 |
Physical properties of metals
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| Research Institution | Foundation for Advancement of International Science |
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Principal Investigator |
OTSUKA Kazuhiro Foundation for Advancement of International Science, Research Development Division, Senior Researcher, 研究開発部, 専任研究員 (50029881)
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| Co-Investigator(Kenkyū-buntansha) |
OHBA Takuya Shimane University, Department of Materials Science, Professor, 総合理工学部, 教授 (00211110)
MORITO Shigekazu Shimane University, Department of Materials Science, Assoc. Prof, 総合理工学部, 助教授 (00301242)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | shape memory alloy / martensitic transformation / Ti-Ni-Cu alloy / synchrotron radiation / high damning material / internal friction / twin / hydrogen / 2段変態 |
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| Research Abstract |
Ti_<50>Ni_<50-x>Cu_x alloys attract much attention recently as vibration-proof materials with high internal friction. These alloys show 2-stage B2-B19(orthorhombic)-B19'(monoclinic) martensitic transformation for 10=x=15, but it is not clear whether they show 2-stage transformation for x>15 or not. Meanwhile, the head researcher previously found that for x>15 the alloys show very high internal friction peak (Q^<-1>=0.2) called "broad peak" at around 250K. In order to understand the origin of the broad peak, it is inevitable to understand the characteristics of the martensitic transformation of the alloys including the compositions x>15.For this purpose we carried out x-ray diffraction experiments with extremely high intensity at synchrotron facilities (SPring-8). Consequently we confirmed the 2^<nd> stage transformation also occurs for x>15, and we could determine the transformation temperatures. Furthermore, very peculiar characteristics were found such that only a very small fraction
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of specimens show the 2^<nd> transformation for 12=x=20. From these results it became possible to separate multiple internal friction peaks. Thus we carried out detailed internal friction experiments using DMA. Consequently we confirmed that the broad peak is a relaxation peak with the following activation energies ; E=0.67eV(x=20),E=0.76eV (x=16). Furthermore, by carrying out single crystal experiments, we found that the broad peak disappears if twins are eliminated by tensile stress. This is a direct evidence to show twins are necessary to observe the broad peak. Meanwhile, there are some reports that hydrogen is necessary to observe the broad peak. By carrying out de-hydrogenation experiments we also confirmed that the broad peak disappear by de-hydrogenation. From these experiments we can conclude that both twin boundaries and H are necessary to observe the high broad peak. Furthermore, we found that a new relaxation peak appears at around 178K after de-hydrogenation. These results are now submitted to Acta Materialia including the discussion of the origin of the broad peak. Less
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Report
(3 results)
Research Products
(11 results)
