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

Prof.
K. Ito


Assoc.Prof.
Y.Mikami


Assoc.Prof.
M.Takahashi
(supplementary assignment)


Assist.Prof.
H.Yamamoto

Geometry modification and W-rich layer formation for weld toe of high-strength low-alloy steel joints using friction stir processing (FSP) with spherical-tip WC tool, resulting in fatigue strength improvement. Cross-sectional macrostructure of the joints (a) as-welded and modified by FSP with tool travel speed of (b) 100 mm/min and (c) 500 mm/min at the constant rotational speed of 800 mm/min (FSP100/800 and FSP500/800, respectively). EPMA-W maps of (d)-(e) the joints with (d)-(e) FSP100/800 and (f)-(h) FSP500/800. S-N diagram obtained by fatigue tests for those specimens.

Designing high bending strength Nb/Cu and Ta/Cu clads produced by explosive welding (EW) with high micro-hardness intermediate layers (ILs) at their interfaces. (a) Bending stress-strain curves of Nb/Cu and Ta/Cu clads at HCV and LCV; (b) & (d), (c) & (e) EBSD-IPF maps of ILs and their TEM bright field images together with SADs of Nb/Cu and Ta/Cu EW clads, respectively.

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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