Microstructure and mechanical property of multi-pass low-strain rolled Mg-Al-Zn-Mn alloy sheet

Abstract Effect of different rolling reductions on the microstructure and mechanical properties of Mg-6Al-3Zn-0.1Mn wt.% alloys were investigated by means of scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The results show that after rolling the as-extruded Mg-Al-Zn-Mn alloy, more second phases are dynamically precipitated. The grains are also gradually refined with increasing the total reduction due to the dynamic recrystallization, and the average grain sizes are estimated to be ∼7.2 μm, ∼3.7 μm, ∼1.2 μm for the as-extruded Mg alloy, ∼34% and ∼60% rolled samples, respectively. On the other hand, the high-density contraction twins have been activated in as-rolled Mg samples, which can effectively separate the Mg matrix and a similar grain refinement effect can be afforded. Moreover, the dislocations are significantly multiplied during the rolling process. Consequently, the tensile strength of the Mg alloy is gradually increased, and the ∼60% rolled Mg alloy exhibits the optimal mechanical properties, with the ultimate tensile strength (UTS) of ∼363 MPa and the elongation of ∼7.2%.