The effect of medium-temperature rolling on microstructure and mechanical properties of extruded Mg–Al–Ca–Mn alloy sheets

The development of low-cost and high-performance magnesium alloy sheets is crucial for lightweight manufacturing. In this study, we demonstrate a medium-temperature rolling process at 250 °C that achieves large plastic deformation in an extruded Mg-1.2Al-0.6Ca-0.4Mn (wt.%) sheet. A multi-scale characterization approach reveals how varying rolling reductions govern microstructural evolution and mechanical properties. The results show that the maximum single-pass reduction without edge cracking under these medium-to-low temperature conditions is ∼ 30%. The sheet processed with a total ∼ 50% reduction over two passes exhibits an optimal mechanical property combination: a yield strength (YS) of ∼ 271 MPa, an ultimate tensile strength (UTS) of ∼ 283 MPa, and a fracture elongation (EL) of 6.6%. Microstructural analysis indicates that increased rolling strain induces significant grain refinement, reducing the average grain size from ∼ 6.7 μm in the as-extruded state to a minimum of ∼ 3.0 μm. Low rolling temperature and large deformation lead to high density of residual dislocations, and more nano-scale Al 8 Mn 5 phase and Al 2 Ca phase are precipitated. Furthermore, large-strain deformation followed by high-temperature annealing effectively weakens and modifies the basal texture, reducing the texture strength from ∼ 29.7 to ∼ 5.4 m.r.d., which contributes to improved ductility. The superior strength–ductility synergy is attributed to the concerted effects of grain refinement, dislocation hardening, precipitation strengthening, and texture modification. This study provides theoretical guidance for the preparation of low-cost and high-performance magnesium alloy sheets and the realization of industrialized and efficient processes.