Dynamic microstructural evolution in Mg-4Zn-2Al-2Sn alloy during hot deformation

The dynamic microstructural evolution of the Mg-4Zn-2Al-2Sn (ZAT422) alloy during hot deformation was studied. The compression tests were carried out under the strain rate of 0.01 s−1 and 5 s−1 at 548 K and the strain rate of 5 s−1 at 648 K. It was shown that the operating mechanisms of dynamic recrystallization (DRX) of ZAT422 alloy during hot deformation were affected by both strain rate and temperature. Parallel or crossed {101¯2} tension twins appeared in the sample deformed to the strain of 0.04 under the strain rate of 0.01 s−1 at 548 K, while new grains with characteristics of discontinuous dynamic recrystallization (DDRX) occurred at corrugated grain boundaries. With the strain rate increasing from 0.01 s−1 to 5 s−1, the effect of twin dynamic recrystallization (TDRX) increased, and necklace structure of DRXed grains formed along the original grain boundaries and the deformation twin boundaries. When the temperature increased to 648 K, continuous dynamic recrystallization (CDRX) occurred within the recrystallized grains, resulting in the further refinement of the microstructure. And it should be noted that TDRX still occurred at this temperature.