Microstructure of weld interface between 6063 and S45C by means of friction stirring was observed by TEM. The reaction layer was formed along welding direction and depth direction of tool insert. The layers were composed of various intermetallic compounds such as Fe2Al5 and FeAl. The constitution differed with welding conditions. At 500 mm/min of welding speed, the interface had a thin reaction layer. At 1000 mm/min of welding speed, the interface had layered structure. However, both of the weld interfaces had a reaction layer under 1 µm and achieved high tensile strength of weld joint.

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MMC (Metal Matrix Composite) has been focused in recent years due to its high strength and wear resistance. Among the dispersion materials of MMC, Titanium Boride (TiB 2 ) exhibits attractive properties in terms of high stiŠness, high hardness and high corrosion resistance. Therefore, it can be used as protection coating of the structural components according to fabrication of thick coatings. In this study, fabrication of TiB 2 dispersed Fe Cr composite coatings was carried out by MA (Mechanical Alloying) method and LPPS (Low Pressure Plasma Spray). It was possible to fabricate TiB 2 dispersed Fe Cr powders by MA method. Furthermore, the thermal sprayed coatings sustained the dispersion structure. Micro Vickers hardness of the coatings increased with the TiB 2 concentration in the coatings. However, FeCr 50 wt. TiB 2 exhibited quite low hardness. It was considered that the excess TiB 2 made the microstructure of the coating porous. Therefore, fabrication of high hardness TiB 2 dispersed Fe Cr coatings was possible according to the selection of moderate TiB 2 mixing ratio. . 緒 言