Deformation behavior and microstructure evolution of Al–5.06Mg–1.67Li–0.51Zn alloy under hot compression

Abstract

The deformation behavior and microstructure evolution of Al–5.06Mg–1.67Li–0.51Zn alloy was investigated under hot compression at a range of temperature from 623 K to 753 K and different strain rates of 0.01–10 s−1. The constitutive equation on hyperbolic sine function and the hot processing maps were established. The hot deformation characteristics of the alloy were studied by optical microscopy and electron backscatter diffraction analysis. It was indicated that the flow stress decreased with the increase of the deformation temperature and the decrease of the strain rate. After the flow stress reached the peak stress at the strain rate of 0.01 s−1, the effects of dynamic recrystallization and work hardening alternated with each other. Meanwhile, the dynamic balance was reached between them, where the flow stress curves appeared periodic fluctuations. With decreasing the lnZ value, the proportion of low-angle grain boundaries in the deformed specimens decreased, and the average misorientation of each grain showed the opposite trend. The low-angle grain boundaries transformed to the high-angle grain boundaries. The migration of high-angle grain boundaries, as well as the merging of sub-grains, was more pronounced. The main dynamic softening mechanism changed from particle-stimulated dynamic recrystallization to geometric dynamic recrystallization and continuous dynamic recrystallization due to the reduced lnZ.