Enhancing the stress corrosion cracking resistance of a low-Cu containing Al-Zn-Mg-Cu aluminum alloy by step-quench and aging heat treatment

The influence of heat treatment on stress corrosion cracking resistance of a low-Cu containing Al-Zn-Mg-Cu aluminum alloy has been investigated. The results show that the stress corrosion cracking resistance is significantly improved by step-quench and aging heat treatment whereas retrogression and re-aging heat treatment and two-stage over aging heat treatment could hardly enhance the stress corrosion cracking resistance compared with peak aging. The improved stress corrosion cracking resistance of the low-Cu containing Al-Zn-Mg-Cu aluminum alloy subjected to step-quench and aging heat treatment is mainly attributed to grain boundary precipitates with high Cu content, large size and discontinuous distribution.