This study compares the microstructural evolution, dynamic recrystallization (DRX) behavior, tensile properties, and age-hardenability between the newly developed high-speed-extrudable BA56 alloy and those of the widely recognized AZ31 alloy in industry. Unlike the AZ31 alloy, which retains partially unrecrystallized grains, the high-speed-extruded BA56 alloy demonstrates a coarser but entirely recrystallized and more homogeneous microstructure. The fine-grained structure and abundant Mg₃Bi₂ particles in the BA56 extrusion billet significantly enhance its DRX behavior, thus enabling rapid and complete recrystallization during extrusion. The BA56 alloy contains band-like fragmented Mg₃Bi₂ particles and numerous fine Mg₃Bi₂ particles distributed throughout the material, in contrast to the sparse Al₈Mn₅ particles in the AZ31 alloy. These features contribute to superior mechanical properties of the BA56 alloy, which achieves tensile yield and ultimate tensile strengths of 205 and 292 MPa, respectively, compared to 196 and 270 MPa for the AZ31 alloy. The superior strength of the BA56 alloy, even with its coarser grain size, can be explained by its elevated Hall-Petch constant and the strengthening contribution from the fine Mg₃Bi₂ particles. Additionally, the BA56 alloy demonstrates significant age-hardenability, achieving a 22% enhancement in hardness following T5 aging, attributed to the precipitation of nanoscale Mg₃Bi₂ and Mg₁₇Al₁₂ phases. By contrast, the AZ31 alloy shows minimal hardening due to the absence of precipitate formation during aging. These findings suggest that the BA56 alloy is a promising candidate for the production of extruded Mg components requiring a combination of high productivity, superior mechanical performance, and wide-ranging process adaptability.

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.