Abstract:In order to improve the stress corrosion cracking resistance of the weldable Al-Zn-Mg alloys with medium strength, the near-solvus pre-precipitation following high-temperature solution treatment was performed on LC52 and 7039 aluminum alloys. The effect of the pre-precipitation on the microstructure, age hardening and stress corrosion cracking of LC52 and 7039 alloy was investigated. The results show that the near-solvus pre-precipitation can be limited on grain boundary and can enhance the discontinuity of grain boundary precipitates. The stress corrosion cracking resistance of aged Al-Zn-Mg alloys can be improved with non-deteriorated strength and plasticity via pre-precipitation.

Key words:  weldablility; Al-Zn-Mg alloys; medium strength; stress corrosion cracking; precipitation; ageing