Development of Diffraction Techniquesfor Studying Phase Transformation (Synchrotron Radiation and High-Resolution Electron Microscopy)

点击翻译按钮获取中文摘要

The results in the present work are summarized as follows.1) By introducing the omega-type magnet into a conventional electron microscope, the energy-filtering electron diffraction method was established. With this method, the strong background in the electron diffraction due to the inelastic scattering could be removed and complicated diffuse scattering resulting from the phase transformation could now be analyzed quantitatively. For example, the precursor effects on the martensitic transformation in Ti50Ni48Fe2 were investigated by the energy-filtering electron diffraction and in situ dark field electron microscopy, and the existence and the growth process of microdomains containing a transverse atomic displacement were clarified for the first time. Also, the short-range order parameter in Cu3Pd was determined quantitatively by the energy-filtered electron diffraction method.2) The kinetics on the nucleation and growth process is an effective approach to investigate the mechanism of first-order phase transformations for non-equilibrium state. In-situ X-ray diffraction data with an accurate temperature controller and highly sensitive detector attached to rota-unit has been obtained from Au-47.5 at%Cd-0.75at.Cu single crystal. It is understood that the nucleus of the low-temperature phase starts from the surface and grows into the inner part gradually.3) High-angle annular detector dark-field scanning transmission electron microscopy, which is much attention as a new technique for high-resolution electron microscopy, is applied for studying the structure of decagonal quasicrystals. Ordered quasicrystals, which can be interpreted from the projection of NaCl-and CsCl-type hypercubic lattices, have been found.