Effect of gradient grain structures on corrosion resistance of extruded Al–Zn–Mg–Cu alloy.

The EXCO and IGC corrosion behavior of an extruded rod of Al–Zn–Mg–Cu alloy with gradient granular grain structure were investigated. The corrosion resistance increased gradually from the center to the surface of the extruded rod due to the increase of distance between η precipitates and the decrease of the precipitate length along grain/sub-grain boundary, which is assumed as the result of the gradually decrease of grain/sub-grain size from the center to the surface. • The precipitate distance along grain boundaries increases with the decrease of grain size of the Al–Zn–Mg–Cu alloy. • The precipitate length along grain boundaries decreases with the decrease of grain size. • The corrosion resistance could be improved with the increase of the distance between η precipitates. [ABSTRACT FROM AUTHOR]