Effect of deformation degree on the mechanical properties of Al-Zn-Mg-Cu alloys: an industrial study

Abstract Hot deformation is a crucial process in the manufacturing of aluminum alloy products, as its parameters exert a profound influence on the ultimate properties of the alloys. This work reports on the Al-Zn-Mg-Cu alloys at a deformation temperature of 450°C, a deformation rate of 5 mm/s, and deformation degrees of 50% and 90% in industrial settings. Following that, an extensive assessment of the alloys’ mechanical characteristics, including their fracture toughness, tensile strength, and fatigue performance. Furthermore, a quantitative analysis of the microstructure was undertaken using OM and EBSD, which revealed that both the average and sub-grain sizes of the two alloys exhibited comparable characteristics. However, the recrystallization fraction showed a difference, with the alloy deformed to 90% exhibiting a higher fraction than the alloy deformed to 50%, while these recrystallized grains are distributed in chains. With the increase of deformation degree from 50% to 90%, the yield and ultimate strengths increase slightly. The opposite law is demonstrated by fatigue crack propagation resistance and fracture toughness. Put otherwise, compared to the alloy deformed to 50%, the alloy deformed to 90% exhibited a faster rate of fatigue crack propagation and a lower fracture toughness. In summary, this research examines how the degree of deformation affects the mechanical characteristics and microstructure of Al-Zn-Mg-Cu alloys.