Abstract
Grain size gradient materials are a type of new structural material with the advantages of both coarse and fine grains. To study the effect of normal gradient grain on the mechanical properties and microstructure of aluminum alloy tube during hydroforming, the normal gradient grain distribution of the outer fine and inner coarse grains was obtained using spinning and annealing methods, and the biaxial stress was acquired using hydraulic bulging experiments. The thickness of the outer refined area was 105, 470, and 570 μm, respectively, where the grain size was refined to within 50 μm. Under biaxial stress, the tensile strength of the tube was 79, 89, and 106 MPa, the maximum expansion rates were 18%, 17%, and 10%, and the work-hardening indexes were 0.19, 0.20, and 0.17, respectively. The gradient grain tube with a refined thickness of 470 μm exhibited both strength and plasticity and was suitable for the hydroforming of aluminum alloy tubular parts. With increasing refined grain area, the density of the low angular grain boundary increased and make the chance of stitching dislocation increased in the process of intracranular deformation. However, the increase in the refined region weakened the deformation coordination, leading to a decrease in plasticity.
Effects of Ce-Rich Mischmetal on Microstructure Evolution and Mechanical Properties of 5182 Aluminum Alloy
