| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2005: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2004: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
To develop high temperature shape memory alloys, B2-type intermetallics such as XTi (X= Pt, Ir, Rh) were noted. It was confirmed that martensitic transformation from B2 to B19 structures occurred around 1000℃ in PtTi. The same martensitic transformation was observed in the ternary compounds, (Pt, Ir)Ti. The low temperature phase was confirmed as B19 structure. The martensitic transformation temperature of (Pt, Ir)Ti increase up to 1200℃. The crystal structure and microstructure of IrTi and RhTi whose structure at low temperature have not been clear yet, were investigated. It was found that the orthorhombic structure appeared in Ir-rich IrTi. In this orthorhombic structure, <100> direction corresponds to <110> direction of B2 structure, which is stable at high temperature. The B2 phase was found in Ti-rich IrTi. This indicates that martensite transformation temperature degreases with increasing Ti contents. The fine twin structure was found in IrTi as same as PtTi or other compounds. The twin plain was identified as {-111}. In RhTi, the phase transformation from B2 to L1_0 phases was observed.
The crystal structure of (Pt, Ir)Ti at low temperature was identified as B19, but super lattice reflection in TEM observation indicates that the structure is more complex although the basic structure is B19. To understand the detailed structure, HAADF-STEM method was performed for ternary compounds. It was found that HAADF-STEM clearly distinguish the atom positions of Pt or Ir and Ti. Thus, the stacking structure with different layer was observed.
The shape recovery and super elasticity was firstly observed in PtTi, IrTi and (Pt, Ir)Ti. These results indicate high potential of PtTi, IrTi, and (Pt, Ir)Ti as high-temperature shape memory alloys.
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