Effect of precipitate state on the stress corrosion behavior of 7050 aluminum alloy

Abstract

The effect of precipitate size and state on stress corrosion property of 7050 aluminum alloy has been investigated for the first time. The results suggest that 7050 aluminum alloy with fine precipitates in matrix and discontinuous copper-rich precipitates at grain boundary exhibits excellent stress corrosion resistance. The different precipitates in matrix lead to electrochemical heterogeneity and different corrosion susceptibility, due to the different coherence with matrix and alloy element matrix solute content. The discontinuous grain boundary precipitates can hinder corrosion cavities connecting into a continuous crack, and copper-rich grain boundary precipitates can retard hydrogen embrittlement, during the stress corrosion process. Furthermore, the in-situ electrochemical impedance spectroscopy (EIS) in real time suggests that precipitate state has obvious influence on passivation during the stress corrosion process. Fine nanoscale precipitates in matrix are beneficial to maintaining continuous passivation, and the copper-rich grain boundary precipitate is beneficial to repassivation.