Achieving ultra-fine grains and high corrosion resistance of Al–Zn–Mg–Cu alloy by ECAP and post cold rolling

The ultra-fine grain structure of Al–Zn–Mg–Cu alloy was prepared by equal channel angular pressing (ECAP) and post cold rolling (CR) combined deformation process. The effect of different rolling deformation on the microstructure, microhardness and corrosion behavior of the ECAP alloy were studied. The results show that with the increase of rolling deformation, the dislocation density increased, the grain and second phases of the deformed alloy were obviously refined. Grain refinement was mainly due to the gradual transformation of some subgrain boundaries and low angle grain boundaries (LAGBs) of deformed alloys into high angle grain boundaries (HAGBs), which eventually form fine grains. The microhardness improvement was attributed to dislocation strengthening, fine grain strengthening and second phase strengthening. Simultaneously, the corrosion behavior of the alloy was tested by immersion corrosion and intergranular corrosion, which revealed that high-density lattice defects, refined grain and second-phase particles can improve the corrosion resistance of the deformed alloys.