Effect of trace Zn addition on microstructure and corrosion behavior of AA2024 under different aging treatments

Abstract

The effect of trace Zn (0.67 wt%) addition on the microstructure and corrosion behavior of AA2024 under different aging treatments was investigated. The results reveal that, with trace Zn addition, the corrosion depth decreases at the natural aging condition, but increases at the artificial aging treatment (both the peak aging condition and over aging condition). The corrosion morphology of the Zn-containing alloy under different aging treatments is also different from that of the Zn-free alloy. Compared with the Zn-free alloy, the dealloying process of the S phase in the Zn-containing alloy is slower, which are not conducive to the formation of pitting corrosion. Transmission electron microscope shows that trace Zn addition can promote the nucleation of the intragranular Guinier-Preston-Bagaryatski zones which transform into S phases in the subsequent aging process. Compared with the Zn-free alloy, the S phases of the Zn-containing alloy are coarser at the over aging condition. Moreover, details of how the corrosion morphology of Zn-containing alloys changed and the relationship between the microstructure and the corrosion behavior were discussed. • Trace Zn inhibits the dealloying of Intermetallic S particles. • The local corrosion depth at the natural aging condition is small and the local corrosion depth at the artificial aging condition is large in the AA2024 with trace Zn compared with the Zn free alloy. • Zn segregated at the S-Al interface has been characterized. • Trace Zn promotes the growth and coarsening of grain boundary S phase particles in the AA2024 under artificial aging treatments. • Zn promotes the coarsening of S phase at the grain boundary and the aggregation of Zn at the S-Al interface works together on the local corrosion morphology of the alloy.