The microstructure and stress corrosion resistance of 6005 A-T6 aluminum alloy joints by friction stir welding were studied using optical microscope

scanning electron microscope and four points bending stress corrosion methods. The results show that the hardness distribution of the joint is W-shape

the lowest hardness appears at the heat affected zone

and the hardness is improved at the weld nugget zone

and the highest hardness appears at the base metal. The main strengthening phase of the base metal is Q’ phase

most of which is disappeared at the weld nugget zone

and where exists lots of dislocation and the main strengthening mechanism is fine grain strengthening

dislocation strengthening and solid solution strengthening. Friction stir welded joint shows good stress corrosion resistance

however corrosive pitting is also happened

and the weakest part of the welded joint is in the heat affected zone.