Enhancing the corrosion resistance of high-strength Al-Zn-Mg-Cu alloys after equal channel angular pressing by developing retrogression and re-aging strategies

In this study, a novel strategy is proposed to address the challenge of balancing strength and corrosion in deformed Al-Zn-Mg-Cu alloys. The alloy was strengthened by equal channel angular pressing (ECAP) and the microstructure was optimized by subsequent retrogression and re-aging (RRA) treatment. The results indicated that the high-density dislocations generated by ECAP in the {111}_Al plane further promoted the precipitation of nanoscale η' phases during the RRA process. The total aging time of RRA was further reduced by 62.5 %, and the average size of the precipitates was also reduced from 5.63 nm before RRA to 4.97 nm. Furthermore, RRA resolves the problems of uneven distribution of precipitated phases and elemental segregation during aging of alloys after ECAP. Reducing the maximum intergranular corrosion depth of the alloy from 86.9 µm to 34.2 µm was achieved by a combination of complex corrosion paths provided by the complex corrosion paths and discontinuous grain boundary precipitation phases.