A novel bottom-up fabrication strategy of heterostructured extruded magnesium alloys based on multiple heterogeneities in as-cast billets

Heterostructured magnesium alloys demonstrate superior mechanical performance. A novel bottom-up fabrication strategy of heterostructures was proposed by preconstructing multiple heterogeneities in rheo-squeeze casting AZ91 billets. The primary α 1 -Mg and α 2 -Mg secondary matrices in the billet exhibited multiple heterogeneities in grain morphology, composition, and β-Mg 17 Al 12 phase (β-phase) distribution. During extrusion, the β-phase governed the dynamic recrystallization and grain growth behaviors through particle-stimulated nucleation and pinning effects. These effects were further modulated by the heterogeneity of β-phase distribution in billets. The secondary matrix exhibited higher β-phase density, consequently enhancing these effects and refining recrystallized grains relative to the primary matrix. This research helps to expand the design strategies for heterostructured alloys.