Effects of Zn and aging condition on mechanical properties and local corrosion behavior of 2056 aluminum alloy

The effects of Zn and aging condition on mechanical properties,intergranular corrosion resistance,exfoliation corrosion resistance and microstructure of 2056 aluminum alloy were investigated by means of tensile testing,intergranular corrosion experiments,exfoliation corrosion experiments,polarization curves measurement and transmission electron microscopy(TEM) analysis.The results show that trace Zn distributes uniformly in the alloy and it can promote the precipitation of S′ phase which can improve the strength and decrease the electrochemistry corrosion kinetics.The precipitation of S equilibrium phases along the grain boundaries decreases and distributes discontinuously,and the precipitate free zone(PFZ) becomes narrower in the alloy containing Zn,which can enhance the exfoliation corrosion resistance and the intergranular corrosion resistance of the alloy.After T8 temper,the strength improves and the plasticity decreases,less S′ phase precipitates uniformly at the grain interface.The precipitation of S equilibrium phases along the grain boundaries decreases and the PFZ becomes much narrower,which can improve the intergranular corrosion resisitance and exfoliation corrosion resistance compared with T6 temper.The test of polarization curves in the 3.5% NaCl solution reveals the same conclusion.