An AZ80 alloy with ultra-high strength and good ductility has been successfully prepared by a novel processing route of combining extrusion and caliber rolling. The caliber rolled (CRed) AZ80 alloy has a necklace grain structure with ultrafine dynamic recrystallized (DRXed) grains formed around the micro-scale deformed grains, which is remarkably different from the uniform microstructure of as-extruded sample free from caliber rolling. In addition, both the deformed region and the DRXed part in CRed AZ80 alloy exhibit more random basal texture than that of the as-extruded sample. Furthermore, the CRed AZ80 alloy demonstrates an excellent comprehensive mechanical property with the ultimate tensile strength of 446MPa and elongation of 13%, respectively. These good mechanical properties of CRed AZ80 alloy can be attributed to the synthetic effects of necklace bimodal microstructure containing ultra-fine grains, profuse Mg₁₇Al₁₂ precipitates, and the modified texture.

An exceptionally high-strength rare-earth-free Mg–8Al–3Bi (AB83) alloy was successfully fabricated via extrusion and caliber rolling. After three-pass caliber rolling, the homogenous microstructure of the as-extruded AB83 alloy was changed to a necklace-like bimodal structure consisting of ultra-fine dynamic recrystallized (DRXed) grains and microscale deformed grains. Additionally, both Mg₁₇Al₁₂ and Mg₃Bi₂ nanoprecipitates, undissolved microscale Mg₁₇Al₁₂, and Mg₃Bi₂ particles were dispersed in the matrix of caliber-rolled (CRed) AB83 alloy. The CRed AB83 sample demonstrated a slightly weakened basal texture, compared with that of the as-extruded sample. Consequently, CRed AB83 showed a tensile yield strength of 398 MPa, an ultimate tensile strength of 429 MPa, and an elongation of 11.8%. The superior mechanical properties of the caliber-rolled alloy were mainly originated from the combined effects of the necklace-like bimodal microstructure containing ultra-fine DRXed grains, the homogeneously distributed nanoprecipitates and microscale particles, as well as the slightly modified basal texture.

A Mg-1.32Bi-0.72Ca (BX11) alloy having bimodal grain structure was successfully prepared by a novel processing route of combining extrusion and three-pass caliber rolling. The first extruded and then caliber-rolled (E-CRed) alloy demonstrates a necklace-like grain structure with ultrafine grains formed around the microscale deformed grains, which is remarkably different from the uniform microstructure of the as-extruded alloy. In addition, the E-CRed BX11 alloy exhibits strong basal texture which is mainly original from the microscale deformed grains. Furthermore, the E-CRed BX11 alloy demonstrates excellent comprehensive mechanical properties, with an ultra-high yield strength of 351 MPa and a good elongation to failure of 13.2%. The significant strength improvement can be mainly attributed to the significant grain refinement and much stronger basal texture compared with the as-extruded sample.