Effects of Enhanced Solution Treatment on Stress Corrosion Behavior of Al-Zn-Mg-Cu Alloy

Effects of enhanced solution treatment (EST) on stress corrosion cracking (SCC) of Al-Zn-Mg-Cu alloy were studied. The results suggest that the volume fractions of AlZnMgCu phase and Al2CuMg phase decreased after EST, thus stress concentrators and crack initiations caused by these residual particles were reduced. However, recrystallization developed further and grains grew coarser at the same time. Compared with the ordinary sample (473°C/1 h + T73), the susceptibility index ISCC values for the EST503 (473°C/1 h + 503°C/1 h + T73) and EST513 condition (473°C/1 h + 513°C/1 h + T73) declined from 11.0% to 7.2% and 9.2%, respectively. However, the susceptibility to SCC increased for the EST523 condition (473°C/1 h + 523°C/1 h + T73) and ISCC became 18.8%, due to excessive recrystallization.