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

Abstract

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 °C are investigated in detail. With the increase of strain rate, the dislocation density increases from 0.06 × 1013 to 3.77 × 1013 m−2, which promotes the dynamic precipitation kinetics. And the volume fraction of η 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 η 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.