New developments on displacive phase transformations

对于该组研究的五个主题，每个主题都描述了结果的摘要。(a)一级位移相变机制：利用平行六面体共振法系统地测定了Ti-Ni，Ti-Ni-Cu，Ti-Ni-Fe合金系马氏体相变前的弹性常数。结果表明，这三种马氏体相变与弹性常数（c '，c_<44>）和弹性各向异性（A_（c_<44>/c'））的温度依赖关系密切。(b)晶格缺陷与一阶位移变换的相互作用：通过引入关于位移变换时的点缺陷的“SC-SRO（对称一致短程有序）原理”（Nature，1997），一致地解释了“橡胶状行为”的长期存在的问题的所有方面。此外，还发现了“微结构记忆”和“双向形状记忆”效应等新现象， ...更多信息 基于该原理发现的（Phys.Rev.Lett.，2000年）。(c)一级位移相变热力学的新途径：对于统一处理非热和等温马氏体相变的Kakeshita理论，进行了系统的实验。从而证明了在磁场作用下等温转变为无热转变，在静水压力作用下无热转变为等温转变等理论的正确性。(d)薄膜中的一级位移相变：用透射电镜系统地研究了Ti-Ni薄膜的结构，发现Ti-Ni薄膜中存在五种沉淀态，它们与成分和时效温度有关。(e)纳米合金颗粒中的一级位移相变：利用TEM和真空蒸发室直接相连的装置，对Au-Cd和Fe-Ni合金纳米颗粒的马氏体相变进行了原位观察。结果发现，合金的相变温度大大降低，但其原因不能用以前的理论来解释。少

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