Recrystallization and microstructure evolution of the rolled Mg-3Al-1Zn alloy strips under electropulsing treatment

The microstructural evolution of rolled Mg-3Al-1Zn (AZ31) alloy during electropulsing treatment (EPT) was analyzed. The results indicate that EPT accelerates tremendously the recrystallization and the microstructure of the rolled Mg-3Al-1Zn alloy is refined. A fine grain microstructure with an average grain size about 2 μm is obtained by the EPT with low duty ratio and high current density (LDRHCD-EPT) at low temperature below 359 K for a short time of 320 s. The EPT has two main effects on the samples, the Joule heat and the athermal effect. Based on the experimental data and the theory analysis, we think that the athermal effect plays a key role in the recrystallization of the deformed alloys under EPT and accelerates the nucleation rate of recrystallization during EPT. Furthermore, the subsequent growth of the recrystallization grains is more dependent on the Joule heat than the athermal effect. As a result, in order to obtain refined recrystallization grains, the athermal effect should be strengthened while the thermal effect should be weakened during EPT.