Study of pre-martensitic phenomena in shape memory alloys by positron annihilation lifetime spectroscopy
| Project/Area Number |
13650720
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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 | Osaka University |
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Principal Investigator |
ARAKI Hideki Department of Materials Science and Engineering, Osaka University, Associate Professor, 大学院・工学研究科, 助教授 (20202749)
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| Co-Investigator(Kenkyū-buntansha) |
MIZUNO Masataka Department of Materials Science and Engineering, Osaka University, Research Associate, 大学院・工学研究科, 助手 (50324801)
SHIRAI Yasuharu Department of Materials Science and Engineering, Osaka University, Professor, 大学院・工学研究科, 教授 (20154354)
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| Project Period (FY) |
2001 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2002: ¥800,000 (Direct Cost: ¥800,000)
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| Keywords | positron annihilation / shape memory alloy / martensitic transformation / pre-martensitic phenomenon / Ni-Ti alloy / positron lifetime / マンテンサイト変態 |
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| Research Abstract |
Many anomalous phenomena have been observed above martensite start(Ms) temperature, such as softening of the shear constants and increasing of internal friction. However, little information has been ohtained about the change in the electron system of the parent phase prior to the martensitic transformation, which should be the origin of all pre-martensitic phenomena. In this work, the pre-martensitic phenomena in NiTi alloys have been studied by positron lifetime spectroscopy which is quite sensitive to electronic-structural changes of matter.
Near-equiatomic NiTi alloys produced by arcmelting were annealed for 180 ks at 1273 K in argon atmosphere for homogenization and subsequently quenched in iced water. The positron lifetime measurements were made at temperatures between 125 and 320 K using a fast-fast timing coincidence system with a time resolution (FWHM) of 190 ps. In order to determine the Ms temperatures the differential scanning calorimetry (DSC) measurements were also carried out in the temperature range between 150 and 350 K.
We have found an anomalous positron lifetime change above martensitic transformation temperature of Ni51Ti49: positron lifetime increases anomalously with decreasing temperature even at temperatures 100 degrees higher than the Ms temperature of the alloy. Almost the same change in positron lifetime also has been observed on the heating run with little hysteresis, which clearly indicates that the observed pre-martensitic change of positron lifetime is due to the intrinsic electronic-structural change of NiTi alloys which causes so-called pre-martensitic phenomena.
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Report
(3 results)
Research Products
(10 results)
