Region of Research

 Mechanisms controlling the joint performance of structural and functional materials, which obtained by fusion welding, liquid-state/solid-state bonding, and solid-state bonding, are metallographically characterized to establish a scientific basis to produce joint materials featuring superior performance. The microstructures of the weld-deposited metal, the heat-affected zone of fusion-welded joints, and the interfacial region of solid-state bounded joint are thoroughly investigated utilizing various methods such as X-ray diffraction, electron-microscopy observation, elementary analysis, EBSP analysis, and numerical modeling and simulation. Formation processes of the microstructures and their relation to joint performance are discussed from the material scientific viewpoint.

Current Research Subjects

  1. Weld microstructure analyses of structural material such as steel
  2. Bonding mechanism of solid-state joining of metals and ceramics, and its application to microstructural control
  3. Application of welding and joining phenomena to development of advanced materials
  4. Synthesis of new functional materials at welding and joining interface
  5. Evaluation of the effect of microstructure on mechanical behavior of structural materials joints

K. Ito


(supplementary assignment)


Friction stir process (FSP) was performed on TIG weld beads in SS400 steel plates. FSP formed the equiaxed fi ne grain structure, which produced signifi cant increase in the number of cycles to failure. The increase became large with decreasing an applied stress amplitude and with decreasing an average grain size (TIG+FSP(L)).

Direct solid-state diffusion bonding of zirconium carbide (ZrC) with ultrahighmelting point of about 3500°C.
(a) Reduction of the bonding temperature by reducing ZrC grain size.
(b)(c) Cross-sectional EBSD images around the bonding interface for the ZrC joints with diff erent average grain size.

Measurement and simulation of deformation behavior at crystalline grain scale of austenitic stainless steel. (a) Orientation map obtained by electron backscatter diff raction (EBSD) technique. (b) Measurement of deformation by digital image correlation (DIC) method. (c) Numerical simulation of microscopic deformation by fi nite element method incorporating crystal plasticity.

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