Significantly improving corrosion resistance of Al−5Zn alloy by adjusting its Zn phase and dislocation distribution

A balance between strength and corrosion resistance in 7xxx series aluminum (Al) alloys is difficult to achieve because of their diverse secondary phases. In this study, the Al−5Zn binary alloy was selected as a simplified representative of the 7xxx series Al alloys, and four distinct equal-channel angular pressing (ECAP) passes of 4, 8, 12, and 16 were used to adjust the Zn phase and dislocation distribution in the alloy. The corrosion behavior and mechanical properties of the alloy were evaluated by performing electrochemical and tensile tests as well as optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results indicate that the Al−5Zn alloy exhibits the highest polarization resistance value and the lowest corrosion current density after 16 ECAP passes. Additionally, its overall mechanical properties with ultimate tensile strength of 224 MPa, yield strength of 199 MPa, and elongation of 21.3% are excellent. The fragmentation and uniform distribution of the Zn phase as well as the even distribution of dislocations contribute to exceptional corrosion resistance and mechanical properties.