2001 Fiscal Year Final Research Report Summary
STRUCTURE CONTROLL AND IMPROVEMENT OF HIGH TEMPERATURE SHAPE MEMORY PROPERYIES OF TiPdNi ALLOY WITH NEW PRECIPITATE PHASE
| Project/Area Number |
12650700
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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 | KUMAMOTO UNIVERSITY |
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Principal Investigator |
NISHIDA Minoru KUMAMOTO UNIVERSITY, GRADUATE SCHOOL OF SCIENCE AND TECHNOLOGY, PROFESSOR, 大学院・自然科学研究科, 教授 (90183540)
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| Project Period (FY) |
2000 – 2001
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| Keywords | SHAPE MEMORY ALLOY / AGING AND PRECIPITATION / ORDER-DISORDER TRNSITION / THERMOELASTIC MARTENSITIC TRANSFORMATION / TRANSMISSION ELECTRON MICROSCOPY / ELECTRON DIFFRACTION / LONG PERIOD STACKING STRUCTURE / ANTIPHASE DOMAIN BOUNDARY |
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| Research Abstract |
Since martensitic transformation temperature of Ti-Pd-Ni alloys can be controlled from ambient temperature to around 800 K by substitutional ratio of Pd and Ni, the application of me alloys have been expected in various fields. To improve the materials properties the microstructure control with precipitation of secondary phase has been attempted in Ti-rich and Pd and Ni-rich alloys.
The authors have found out that quenched Ti_<45>Pd_<45>Ni_<10> alloy shows peculiar phase transformations. Upon heating in DSC measurement, an endothermic reaction occurs firstly around 373 K, which corresponds to the reverse martensitic transformation from B19 to B2 structure. Subsequently, a pair of exothermic and endothermic peaks is observed from 550 to 740 K, which is due to the appearance and disappearance of new order phase with long period stacking structure. One of characteristic feature in electron diffraction pattern of the new phase is superlattice spots at 1/8 position in the row of reflections of 111_<B2>*. Finally, an exothermic reaction which corresponds to the formation of Ti_2(PdNi)_3 phase is detected around 850 K. More interesting phenomenon, which is the parent phase stabilization with low temperature aging below 500 K, is discovered. The ω diffuse streak with rather strong intensity is observed in electron diffraction patterns taken from the stabilized B2 phase. It is confirmed that the diffuse streak is a kind of precursor phenomena of the ordering. Morphological and crystallographic aspects of the new order phase are also discussed. The reversible shape memory effect can be generated by using the new order phase. However, the amount of shape change is smaller than that of Ni-rich Ti-Ni alloy with Ti_3Mi_4 precipitates.
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