Enhancing Stress Corrosion Cracking Resistance in a High Alloying Al–Zn–Mg–Cu Alloy by Controlling Recrystallization Morphology

Al–Zn–Mg–Cu alloys are widely used in aerospace, with recrystallization significantly influencing their stress corrosion resistance. This study examines the impact of recrystallization morphology on corrosion resistance in a high-alloying Al–Zn–Mg–Cu alloy, focusing on lath-shaped and equiaxed recrystallized grains. The findings reveal that, at the same recrystallization fraction, the equiaxed sample has a 2.83 times higher corrosion current density and a 1.15 times higher stress corrosion cracking susceptibility index than the lath sample. However, its critical stress intensity factor is only 89.3% of the lath alloy's. Lath recrystallization demonstrates superior stress corrosion resistance due to larger grain sizes, wider grain boundary precipitate spacing, lower Zn and Mg content, and higher Cu content. Finite element simulations and in-situ tensile tests show that the equiaxed sample experiences more stress concentration and cracking at grain boundaries under the same applied stress. These results provide insights into optimizing the stress corrosion resistance of Al–Zn–Mg–Cu alloys.