Improved continuous precipitation kinetics and tensile properties of extruded AZ80 alloy through {10–12} twin formation

Abstract

This study investigates the effect of {10–12} deformation twins on the continuous precipitation behavior of an extruded Mg–8.0Al–0.5Zn–0.2Mn (AZ80) alloy during aging. The extruded AZ80 alloy is compressed along the transverse direction to introduce {10–12} twins, followed by an aging treatment at 300 °C. The extruded material exhibits a twin-free microstructure with low internal strain energy, whereas the pre-twinned material possesses abundant {10–12} twins and has high internal strain energy. The aging results reveal that the peak-aging time of the pre-twinned material (1 h) is one-eighth of that of the extruded material (8 h). Although Mg17Al12 continuous precipitates (CPs) are observed in both the peak-aged materials, these CPs are much smaller and more densely distributed in the pre-twinned material despite the significantly shorter aging time. The CPs size in the peak-aged materials increases in the following order: twinned region in the pre-twinned material (0.47 µm) < residual matrix region in the pre-twinned material (1.71 µm) < matrix region in the extruded material (2.55 µm). Moreover, the CPs number density in the twinned region of the pre-twinned material is approximately 11 times higher than that in the matrix region of the extruded material. The peak-aged pre-twinned material exhibits significantly higher tensile strength and ductility than the peak-aged extruded material. These results demonstrate that the formation of {10–12} twins in the extruded AZ80 alloy substantially accelerates the static precipitation of CPs during aging at 300 °C and improves the tensile properties of the peak-aged material.