抄録
The 6061-0 aluminum alloy sheet with two millimeter thick was welded by friction-stir-welding (FSW) at various welding conditions. Microstructure of the welds was investigated by optical microscopy in order to characterize the plastic flow pattern in the weld and change in size and morphology of the matrix grain structure from the original pancake-like structure in the parent sheet. The transverse cross section in the weld revealed that the boundary between the stir zone and the TMAZ (thermo-mechanically-affected-zone) exhibited a linear shape from the top to the bottom through the sheet thickness. An onion-ring pattern, which was common in the friction-stir-welded thick plate, was not detectable in the present stir zone. The wavy striations were observed in the transverse- and longitudinal-cross section of the weld. These were traces of the oxide films on the butt surface of the parent sheet and these provided the base for the evaluation of characteristic plastic flow in the friction-stir welded thin sheet. Yield strength and UTS of the weld were almost equivalent to those of the parent sheet. On the other hand, the reduced elongation was obtained. The weld was shown to break in the HAZ (heat-affected-zone).
