Improving mechanical anisotropy and corrosion resistance of extruded AA7075 alloy by warm cross rolling and annealing

Abstract

The anisotropy of mechanical properties and poor corrosion resistance are important problems for high strength aluminum plate. In this study, the combined process of hot extrusion and warm cross rolling was conducted on AA7075 alloy, and both the extruded and rolled plates were annealed at various temperatures. The effects of warm cross rolling and annealing on the microstructure, mechanical properties, and corrosion behavior were studied. The results indicated that both cross rolling and annealing weakened the intensity of main textures of brass, Dillamore, and S. Compared to the extruded plate, the cross rolled ones exhibited higher hardness, higher conductivity, and lower anisotropy of tensile strength. Both cross rolling and annealing made the tensile strength of a plate along different directions more uniform. Moreover, annealing greatly enhanced the corrosion resistance by consuming the distortion energy, reducing the number of crystalline defects and increasing the fraction of low-Σ coincident site lattice grain boundaries. After annealing, the rolled AA7075 plates exhibited better corrosion resistance than the extruded ones, since they possessed lower fractions of brass texture, finer grains, and higher fraction of low-Σ coincident site lattice grain boundaries.