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

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

Prof.
K. Ito


Assoc.Prof.
M.Takahashi
(supplementary assignment)


Assist.Prof.
H.Yamamoto


Assist.Prof.
S.M.Hong


 


 


 


 


 


Welding-time variation of penetration shape change in the simulated vibration assisted tandem-pulsed GMAW using the Flow-3D commercial software in the presence of sine-vibration parallel to the welding direction (250 Hz) and the surface tension active elements.


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.


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.


Strengthening of Al/Cu dissimilar joints due to complicated interface produced by pulsed TIG welding with a constricted nozzle; (a) 3D-interfacial structure, (b) top-view and (c) cross-sectional transmission images of the hook-shaped interface reaction layer (yellow), constructed using about 30 images (a serial sectioning technique), in comparison with its (d) top-view and (e) cross-sectional OM images.

 
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