Microstructure Evolution of the Near-Surface Deformed Layer and Corrosion Behavior of Hot Rolled AA7050 Aluminum Alloy

The current study investigates the influence of hot rolling on the microstructure evolution of the near-surface region on AA7050 aluminum alloy and the corrosion performance of the alloy. It is revealed that hot rolling resulted in grain refinement in the near-surface region, caused by dynamic recrystallization, and equiaxed grains less than 500 nm can be clearly observed. Fibrous grains were evident in the hot rolled AA7050 aluminum alloy with relatively lower rolling temperature or larger rolling reduction, caused by the more severe elemental segregation at grain boundaries, which inhibited the progression of dynamic recrystallization. The density of the precipitates in the fibrous grain layer was higher, compared with those in the equiaxed grain layer, due to the increased dislocation density, combined with more severe elemental segregation, which significantly promoted the nucleation of precipitates. With the co-influence exerted by low density of precipitates and dislocations on the improvement of the corrosion performance of the alloy, the rolled AA7050 alloy with decreased density of precipitates and dislocations exhibited better corrosion resistance.

Automated summary

This study investigates the effect of hot rolling on the microstructure and corrosion performance of AA7050 aluminum alloy. It is found that hot rolling leads to grain refinement in the near-surface region due to dynamic recrystallization, and equiaxed grains with a size less than 500 nm are observed. Fibrous grains are observed in hot rolled AA7050 alloy with lower rolling temperature or larger reduction, attributed to severe elemental segregation at grain boundaries, which inhibits dynamic recrystallization. The density of precipitates in the fibrous grain layer is higher compared to the equiaxed grain layer, promoting nucleation of precipitates due to increased dislocation density and elemental segregation. Rolled AA7050 alloy with decreased density of precipitates and dislocations exhibits better corrosion resistance.