2000 Fiscal Year Final Research Report Summary
New developments on displacive phase transformations
| Project/Area Number |
09242103
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Research Institution | University of Tsukuba |
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Principal Investigator |
OTSUKA Kazuhiro University of Tsukuba, Institute of Materials Science, Professor, 物質工学系, 教授 (50029881)
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| Co-Investigator(Kenkyū-buntansha) |
TADAKI Tsugio Osaka Women's University, Faculty of Science, Professor, 理学部, 教授 (90029885)
SABURI Toshio Kansai University, Faculty of Engineering, Professor, 工学部, 教授 (40029020)
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| Project Period (FY) |
1997 – 1999
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| Keywords | displacive phase transformation / martensitic transformation / pretransformation phenomena / lattice defects / kinetics of transformation / shape-memory thin films / nano-particles / lattice softening |
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| Research Abstract |
For the five themes studied in this group, the abstracts of the results are described for each theme.
(a) The mechanism of 1st order displacive transformations : The elastic constants of Ti-Ni alloy system (Ti-Ni, Ti-Ni-Cu, Ti-Ni-Fe) were measured systematically by utilizing "the parallelepiped resonance method" prior to the martensitic transformations. As a result, close relations were found to exist between the three kinds of martensitic transformations and the temperature dependence of elastic constants (c', c_<44>), and elastic anusotropy (A ≡ c_<44>/c').
(b) The interaction of lattice defects with 1st order displacive transformation : The all aspects of the long-standing problem of "rubber-like behavior" was consistently explained by introducing "SC-SRO (Symmetry-Conforming Short Range Order) principle" (Nature, 1997) with respect to point defects upon displacive transformation. Furthermore, other new phenomena such as "microstructure memory" and "two-way shape memory" effects were
… More
found based on this principle (Phys.Rev.Lett., 2000).
(c) New approach to thermodynamics of 1st order displacive transformations : For Kakeshita's theory, who treated athermal and isothermal martensitic transformations in a unified manner, systematic experiments were carried out. Thus the theory was justified by showing that an isothermal transformation will change into athermal one under magnetic field, and an athermal one into an isothermal one under hydrostatic pressure etc.
(d) 1st order displacive transformations in thin films : The structures of Ti-Ni thin films produced by sputter-deposition technique were systematically studied by TEM.As a result, five precipitation states were found to exist as a function of composition and aging temperature.
(e) 1st order displacive transformations in nanometer-sized alloy paricles : The martensitic transformations of nano-particles of Au-Cd and Fe-Ni alloys were observed in-situ by TEM, by using a newly developed apparatus directly connected TEM and vacuum evaporation chamber. As a result, the transformations temperatures of the alloys were found to decrease greatly, but the cause was found not to be explained by the previous theory. Less
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