Microstructure, Non-Basal Texture and Strength-Ductility of Extruded Mg-6Bi-3Zn Alloy

To investigate the influence of Zn-alloying on the microstructure and tensile mechanical properties of Mg-6Bi alloy after hot extrusion, a new ternary Mg-6Bi-3Zn alloy was prepared by extrusion at 300 °C. The microstructures, texture, dynamic precipitates and tensile mechanical behaviors of the extruded alloy were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), electron backscattered diffraction (EBSD) and a material testing machine at room temperature. After extrusion, the Mg-6Bi-3Zn alloy possesses a bimodal microstructure with elongated large unrecrystallized (unDRXed) grains and fine dynamic recrystallized (DRXed) grains. In addition, non-basal <202_1>//ED, <448_3>//ED and <112_1>//ED textures are observed within DRXed grains due to the Zn addition, leading to texture weakening in the extruded Mg-6Bi-3Zn alloy. Zn addition facilitates the dynamic precipitation behavior, leading to a 12.2% area fraction of Mg₃Bi₂ precipitates with an average size of 39.2 nm. Furthermore, incorporation of Zn atoms in Mg₃Bi₂ phases and segregation of Zn at the grain boundary are found. The extruded Mg-6Bi-3Zn alloy exhibits a tensile strength of 336 ± 7.1 MPa and a yield strength of 290 ± 5.5 MPa, as well as an elongation of 11.5%. Therefore, Zn addition is beneficial to enhance strength and keep good ductility for the extruded Mg-6Bi-3Zn alloy.