The Dynamic Recrystallization in a Hot-Compressed Al-Zn-Mg-Cu-Sc-Zr Alloy: the Role of Strain Rate

The effects of strain rates (0.001-1 s-1) on the microstructures and mechanical performance of the novel Al-Zn-Mg-Cu alloy through hot compression at 300 degrees C are investigated in detail. With the increase of strain rate, the dislocation density increases from 0.06 x 1013 to 3.77 x 1013 m-2, which promotes the dynamic precipitation kinetics. And the volume fraction of eta precipitates is calculated by the differential scanning calorimetry curves increasing from 1.36% to 3.94%. Both dislocations and precipitates promote to increase the hardness of the Al-Zn-Mg-Cu alloy. The large number of eta precipitates in high-strain-rate samples hinders the recrystallization process by impeding the movement of dislocations and grain boundaries, decreasing the volume fraction of recrystallized grains to 3.1%. Continuous/discontinuous dynamic recrystallization occurs preferentially at low strain rates, and discontinuous dynamic recrystallization is rarely observed in high-strain-rate samples. In addition, because the process of continuous dynamic recrystallization promotes the transformation from low-angle grain boundaries to high-angle grain boundaries, more continuous dynamic recrystallized grains and less low-angle grain boundaries can be observed in low-strain-rate samples. With increasing strain rate, the dislocation density and the volume fraction of precipitates gradually increase, resulting in an increase in sample hardness. In addition, continuous/geometric dynamically recrystallized grains occur in all samples, whereas discontinuous dynamic recrystallization occurs preferentially in low-strain-rate conditions due to the lack of eta precipitate pinning. Low-strain-rate samples have more recrystallized grains.image (c) 2023 WILEY-VCH GmbH