Abstract:The annealing tests heated by pulsed current (PC) or furnace for AZ31B magnesium sheets were carried out, and the effects of PC on the microstructure and dislocation density of the alloy were analyzed. The results show that PC strengthens the migration of boundaries, and then the twin grains, most of which distribute in the coarse grains, “spheroidize” to equiaxed grains, thus separating the coarse grains and refining the microstructure. This process homogenizes the initial microstructure and eliminate the typically lamellar twin grains. Moreover, PC also strengthens the dislocation annihilation. When the specimens were annealed by PC at 300 °C for 4 min, the dislocation density was even lower than that annealed by furnaces at 400 °C for 3 h before deformation. Furthermore, dislocation annihilation is enhanced with the increase of peak current density and the decrease of pulsed frequency.

Key words: pulsed current; AZ31B magnesium alloy; annealing; microstructure evolution; twinning; dislocation annihilation