Flow stress and microstructural evolution of the horizontal continuous casting Al-0.96Mn-0.38Si-0.18Fe alloy during hot compression

Hot compression tests of the horizontal continuous casting Al-0.96Mn-0.38Si-0.18Fe alloy were preformed on Gleeble-1500 system in the temperature range from 350°C to 500°C and at strain rate range from 0.01s^-1 to 10s^-1, and the associated microstructural changes were studied by the observations of optical metallographic and transmission electron microscope. The results show that the flow stress below 450°C and at higher strain rates increases with increasing strain and tends to be constant after a peak value, showing a steady state flow until high strains. While above 450°C and at lower strain rates, the flow stress reaches a plateau and then decline slightly, showing a flow softening. The peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener-Hollomon parameter in the hyperbolic-sine equation with the hot deformation activation energy of 159.24kJ/mol. The steady state flow results from dynamic recovery whereas flow softening is associated with dynamic recrystallization and dynamic transformation of precipitates. The designed columnar coarse grains were capable of GDRX above 450°C and at lower strain rates.