Radial-shear rolling of high-strength aluminum alloys: Finite element simulation and analysis of microstructure and mechanical properties

The effect of high-temperature radial-shear rolling (RSR) on the strain and stress distributions in the cross-sections of processed rods has been studied using finite element method simulation for the industrial 7075 alloy and compared with that for the new Al7Zn2.8Mg0.7Ni0.55Fe0.2Zr alloy. The simulation has revealed a gradient strain distribution along the cross-section of the processed rods for both alloys. The lowest stress has been observed in the central part of the rods, whereas the peripheral zones have had the highest strain with a factor of more than 1.5. For both alloys, the maximum true strain localized in the peripheral zones of the rods (similar to 10) has proven to be substantially higher than the true strain (similar to 2.1) caused by change in the overall (linear) dimensions of the rods. The results of numerical simulation of the stress and strain distributions have been in a good agreement with the as-deformed structure. For example, we have observed the formation of a gradient structure consisting of deformed fibrous grains in the central parts of the rods (in the vicinity of their axes) whereas in the middle of rod diameter and in the surface layers that are exposed to the highest stress and strain the structure contained more equiaxed and finer grains formed during dynamic recrystallization. The results of uniaxial tensile tests have revealed that the mechanical properties of the 7075 alloy (UTS similar to 390 MPa, YS similar to 280 MPa and delta similar to 9.9%) after RSR are comparable to those of the new alloy the microstructure of which additionally contains fine intermetallic particles. Thus, radial-shear rolling can be considered as an efficient industrial technology of high-strength aluminum alloys allowing one to achieve a combination of high strength and ductility in as-processed materials with a gradient grain structure.