Effects of microstructures on corrosion and stress corrosion behaviors of an Al-12.1 at.% Zn alloy

Various heat treatments of an Al-12.1 at. % Zn alloy would bring forth vari ous types of microstructures such as solid solution (SS), continuous precip itation (CP), and discontinuous precipitation (DP), each of which contain r espective shares of distribution of the aluminum-rich phases (cuo, cu) and the zinc-rich phase (beta), and the corrosion behaviors of the said alloy m ay be affected as a result. Electrochemical measurements conducted in a 3 w t. % NaCl solution indicate that respective corrosion rates should be evinc ed in the following order: supersaturated SS < DP < CP, The difference in m icrostructures can also exert an influence on stress corrosion cracking (SC C) of the said alloy. Stress corrosion cracks propagate predominantly in an intercrystalline mode. However, the severe corrosion of precipitation site s may incur a change in crack propagation under applied stress. In that cas e, patches of transgranular fractures are found interspersed in the intergr anular mode.