Abstract: Bimodal magnesium (Mg) alloys exhibit a favorable strength-ductility synergy through the interaction between dynamically recrystallized (DRXed) and unDRXed regions. However, the influence of orientation configurations within DRXed regions on the deformation behavior remains insufficiently understood. In this study, four bimodal AZ31 samples with comparable DRXed grain sizes and fractions but distinct grain orientation configurations were fabricated via hot extrusion. The global and local orientation configurations of soft-oriented DRXed grains (basal Schmid factor > 0.3) were quantitatively assessed. A soft-surrounding-soft configuration facilitated early basal slip and enhanced ductility but led to pronounced plastic incompatibility and low yield strength (YS). A hard-surrounding-soft configuration increased but limited ductility due to poor slip transfer. In contrast, the B1 sample exhibited a (soft+hard)-surrounding-soft configuration that moderated stress gradients and enhanced crack resistance, achieving the best strength-ductility combination. These findings highlight the critical role of multiscale orientation configurations within DRXed regions in controlling deformation mechanisms and provide guidance for designing high-performance bimodal Mg alloys.

Key words: Magnesium alloys, Bimodal grain structure, Texture, Strain partitioning, Crack propagation