Research on the anisotropy of microstructure, mechanical properties, and residual stress of 7055 aluminum alloy profile with complex section

7055 aluminum alloy is a typical lightweight metal widely used in the aerospace field, where components require a uniform microstructure and high mechanical properties. In this paper, reverse extrusion experiments were conducted on a large-section 7055 aluminum alloy profile by using a 150MN reverse extruder. The microstructure, mechanical properties, and residual stress at the positions with different aspect ratios on the profile section were compared and analyzed to elucidate the correlations among these three aspects. The results show that the Brass texture and S texture are formed in the position with a large aspect ratio, which is mainly (112)// ED (Extrusion Direction) fiber orientation. The grains are flat and the anisotropy of mechanical properties is low. As the aspect ratio decreases, the grains transform into a cylindrical shape and the texture types shift towards Copper texture, EXa texture, and Goss texture. Concurrently, the fiber orientation gradually changes to (100) and (111) //ED, resulting in an increase in strength in the ED and an enhanced degree of anisotropy. At the macroscopic level, the yield strength in different directions determines the magnitude of the type I residual stress components. At the microscopic level, the dislocation density is a crucial factor influencing the type I residual stress. The stronger the anisotropy in dislocation density components, the more pronounced the anisotropy in type I residual stress. Second-phase particles and the pinned dislocations can cause significant type III residual stress. Dislocations can balance the inhomogeneous elastic strain on both sides of the dislocation by producing the type III residual stress, and the greater the orientation difference between the two sides of the dislocations, the higher the value of type III residual stress is.