Microstructure regulation of Mg–2Zn–0.4Ca magnesium alloy by rolling speed for enhanced biocorrosion resistance

This study investigated the effects of rolling speed on the microstructure, mechanical properties, and corrosion behavior of Mg–2Zn–0.4Ca magnesium alloy in SBF. The results indicate that rolling speed strongly controls dynamic recrystallization (DRX), grain size, and dislocation density. Although the sample rolled at 768 mm/s showed a relatively high fraction of DRXed grains, retained coarse deformed grains and high GND density caused pronounced microstructural inhomogeneity. At 1024 mm/s, the alloy obtained the finest average grain size (3.51 μm) and the lowest dislocation density, achieving a good balance between grain refinement and defect regulation. Consequently, its ultimate tensile strength (UTS) and elongation (EL) reached 291.39 MPa and 9.9%, respectively. When the rolling speed increased to 1280 mm/s, DRX was suppressed, while the fractions of deformed grains and unindexed regions increased, leading to degraded mechanical properties. Corrosion tests revealed that the 1024 mm/s sample had the lowest corrosion rate, hydrogen evolution volume, and corrosion current density, owing to its homogeneous microstructure, reduced local distortion, and dense, stable corrosion product layer. Overall, moderate rolling speed can synergistically improve microstructural uniformity, mechanical properties, and corrosion resistance, providing guidance for plastic processing of biodegradable Mg alloy sheets.