Dislocation characteristics and dynamic recrystallization in hot deformed AM30 and AZ31 alloys

Zn addition to Mg alloys activates non-basal slip or twinning with solute softening effects. On the other hand, the effects of the Zn solute on the macroscopic dislocation behavior and dynamic recrystallization are not completely understood. Moreover, it is unclear if <c+a> slip can be affected by changes in the c/a ratio of solute atoms. This study was conducted to understand the solute strengthening of Zn addition and its effects on the dislocation characteristics and dynamic recrystallization. A hot torsion test was performed on both AM30 and AZ31 alloys up to a high strain to investigate the Zn solute effect on the dislocation characteristics and dynamic recrystallization. The dislocation components of the hot torsioned alloys were evaluated by X-ray line profile analysis and electron backscatter diffraction. The results showed that the Zn solutes slightly accelerate strain accumulation at the initial stages of hot deformation, which accelerated recrystallization at high strain. The dislocation characteristics were changed dynamically by Zn addition: fortified <c+a>-type slip, dislocation arrangement and strain anisotropy parameters. The most important point was that the dislocation characteristics were changed dramatically at the critical strain for recrystallization and high strain regions. The addition of Zn also acted greatly in these strain areas. This indicates that the rapid formation of <c+a>-type slip at the serrated grain boundaries occurs at the initiation of dynamic recrystallization and the increase in the grain triple junction because grain refinement has a great influence on the dislocation characteristics at high strain.