Grain refinement and enhanced mechanical properties of rolled and annealed Mg–3Al alloy through trace Ca addition

• Minor Ca addition (0.2 wt.%) to Mg–3Al alloy induces Al 2 Ca particle formation. • Al 2 Ca particles promote {10–11}–{10–12} double twinning in the as-rolled microstructure. • Double twins act as nucleation sites, enhancing static recrystallization during annealing. • Ca-added AX30 alloy exhibits finer grains and stronger basal texture after annealing. • AX30 alloy achieves 48% higher strength–ductility product than the Ca-free A3 alloy. This study investigates the effect of trace Ca addition on the microstructural evolution and mechanical properties of an Mg–3Al (A3) alloy. The addition of 0.2 wt.% Ca leads to the formation of thermodynamically stable Al 2 Ca phase. These Al 2 Ca particles act as localized stress concentrators during deformation, altering the twinning sequence by reducing the activity of {10–12} extension twins and facilitating the formation of {10–11}–{10–12} double twins, which ultimately provide additional nucleation sites for recrystallization during subsequent annealing. Consequently, the annealed Mg–3Al–0.2Ca (AX30) alloys exhibit a finer recrystallized grain structure compared to the annealed A3 alloy, while retaining a strong basal texture. These microstructural features contribute significantly to the strength enhancement in the annealed AX30 alloy, primarily through improved grain boundary and texture strengthening. Theoretical yield strength estimations, accounting for contributions from five mechanisms—grain boundary, dislocation, texture, solid solution, and particle strengthening—closely match experimental results, with grain boundary and texture effects identified as dominant. The AX30 alloy annealed at 350 °C exhibits the highest elongation among the tested conditions, attributed to its reduced dislocation density and refined grain structure. As a result, the overall tensile property, defined as the product of yield strength and elongation, is improved by up to 48% with the addition of 0.2 wt.% Ca to the A3 alloy. These findings demonstrate that even trace Ca additions can effectively tailor microstructure and substantially enhance the mechanical properties of Mg–Al sheet alloys.