Microstructure

mechanical properties and electrochemical corrosion properties of bobbin-tool friction stir welding（FSW）for the 7075 aluminum alloy were studied. The results show that

the welding zone is composed of weld nugget

thermo-mechanically affected zone

heat affected zone and base metal. The weld nugget is composed of fine equiaxed grains

the heat affected zone is composed of coarse deformed grains and the heat affected zone is coarse microstructure of base metal. Due to grain refinement and mechanical work hardening

the hardness of welding zone is markedly improved. However

the tensile strength has no significant increase

which is only 267.84 MPa. The boundary of retreating side and base metal is fuzzy

consisted of inhomogeneous mixed-grain microstructure

which is responsible for the low strength. The corrosion resistance of the surface perpendicular is better than that of the parallel to the weld joint

but the corrosion resistance of the welding zone is worse than that of the base metal.