Effect of Mn content on the hot deformation behavior and microstructure evolution of Al–Mg–Mn 5xxx alloys

The hot deformation behaviors of Al–Mg–Mn 5xxx alloys with different Mn contents (0.1–1 wt.%) were studied by carrying out uniaxial compression tests over the temperature and strain rate ranges of 350–500 °C and 0.001–1.0 s−1, respectively. In the pre-deformed state, Mn dispersoids appeared in the α-Al matrix once the Mn content reached 0.4%. The density of these dispersoids increased with a further increase in the Mn content. The peak flow stress gradually increased with an increase in the Mn content under a given deformation condition owing to the strong strengthening effect of the dispersoids, and the activation energy of hot deformation also increased with increasing Mn content. The deformed microstructures were analyzed using the electron backscatter diffraction technique, and the dominant restoration mechanisms were classified based on the Zener-Hollomon parameter (Z). Under low-Z deformation conditions, continuous dynamic recrystallization (CDRX) was the principal softening mechanism. At intermediate Z values, CDRX was partially accompanied by particle-stimulated and discontinuous DRX. At higher Z values, dynamic recovery was the only softening mechanism, which was mainly dominated by work hardening.